Model-specific capabilities

Additional source and measure features:

• Model 2601B, 2602B, and 2604B System SourceMeter^® instruments:
  • Source ±DC voltage from 5 µV to 40.4 V
  • Source ±DC current from 100 pA to 3.03 A
  • Source ±pulse current up to 10 A
  • Measure ±pulse current up to 10 A
  • Measure ±DC voltage from 100 nV to 40.8 V
  • Measure ±DC current from 100 fA to 3.06 A
• Model 2611B, 2612B, and 2614B System SourceMeter^® instruments:
  • Source ±DC voltage from 5 µV to 202 V
  • Source ±DC current from 2 pA to 1.515 A
  • Source ±pulse current up to 10 A
  • Measure ±pulse current up to 10 A
  • Measure ±DC voltage from 100 nV to 204 V
  • Measure ±DC current from 100 fA to 1.53 A
• Model 2634B, 2635B, and 2636B System SourceMeter^® instruments:
  • Source ±DC voltage from 5 µV to 202 V
  • Source ±DC current from 1 fA to 1.515 A
  • Source ±pulse current up to 10 A
  • Measure ±pulse current up to 10 A
  • Measure ±DC voltage from 100 nV to 204 V
  • 2635B and 2636B: Measure ±DC current from 100 aA to 1.53 A
  • 2634B: Measure ±DC current from 1 fA to 1.53 A

Voltage and current

The following table lists the source and measure limits for the voltage and current functions. The full range of operation is explained in Operating boundaries.

Source V

When configured to source voltage (V-source) as shown in the figure below, the 2600B functions as a low-impedance voltage source with current limit capability and can measure current (I-meter) or voltage (V-meter).

Sense circuitry is used to monitor the output voltage continuously and make adjustments to the V‑source as needed. The V-meter senses the voltage at the HI / LO terminals (2-wire local sense) or at the device under test (DUT) (4-wire remote sense using the sense terminals) and compares it to the programmed voltage level. If the sensed level and the programmed value are not the same, the V‑source is adjusted accordingly. Remote sense eliminates the effect of voltage drops in the test leads, ensuring that the exact programmed voltage appears at the DUT. With 4-wire sensing enabled, both remote sense leads must be connected or incorrect operation occurs. For the 2601B, 2602B, 2611B, 2612B, 2635B, and 2636B, use contact check to verify that the sense leads are connected (see Contact check measurements).

Source I

When the instrument is configured to source current (I-source), as shown in the figure below, the instrument functions as a high-impedance current source with voltage limit capability and can measure current (I-meter) or voltage (V-meter).

For 2-wire local sensing, voltage is measured at the HI / LO terminals of the instrument. For 4-wire remote sensing, voltage is measured directly at the device‑under‑test (DUT) using the sense terminals. This eliminates any voltage drops that may be in the test leads or connections between the instrument and the DUT.

The current source does not require or use the sense leads to enhance current source accuracy. However, if the instrument is in 4-wire remote sense mode, the instrument may reach limit levels if the sense leads are disconnected. With 4-wire remote sensing selected, the sense leads must be connected or incorrect operation results.

Source I measure I, source V measure V

The System SourceMeter^® instrument can measure the same function that it is sourcing. For example, when sourcing a voltage, you can measure voltage. Conversely, if you are sourcing current, you can measure the output current. For these operations, the measure range is the same as the source range.

This feature is valuable when operating with the source in compliance. When in compliance, the programmed source value is not reached, so measuring the source lets you measure the actual output level.

Measure only (voltage or current)

The figures below show the configurations for using the instrument exclusively as a voltmeter or ammeter.

As shown in the following figure, to configure the instrument to measure voltage only, set it to source 0 A and measure voltage.

Set the voltage limit to a level that is higher than the measured voltage. If the voltage limit is set to a level that is lower than the measured voltage, excessive current flows into the instrument. This current could damage the instrument. Also, when connecting an external energy source to the instrument when it is configured as a current source, set the output off state to the high-impedance mode. See Output-off states for more information on the output-off states. See “Limits” in the Model 2600B User's Manual for details on compliance limits.

In the following figure, the instrument uses a 2-wire local sensing configuration and is set to measure current only by setting it to source 0 V and measure current. Note that to obtain positive (+) readings, conventional current must flow from HI to LO.

Contact check

The Models 2604B, 2614B, and 2634B do not perform contact check measurements.

When a contact check measurement is made, two small current sources switch between the HI and SENSE HI terminals and the LO and SENSE LO terminals. By controlling the switches illustrated in the following figure, the current from these sources flows through the test leads and through the contact resistance, as shown. To accurately measure the resulting contact resistance, the differential amplifier outputs are measured once with the current sources connected, and again with the current sources disconnected. This allows for compensation of various offset voltages that can occur.

Autozero

The ADC of the 2600B uses a ratiometric analog to digital (A/D) conversion technique. To ensure reading accuracy, the instrument must periodically obtain fresh measurements of its internal ground and voltage reference. Separate reference and zero measurements are used for each aperture.

As summarized in the table below, there are different settings for autozero. By default, the instrument is set to AUTO, which automatically checks these reference measurements whenever a signal measurement is made. If the reference measurements are out of date when a signal measurement is made, the instrument automatically makes two more A/D conversions, one for the reference and one for the zero, before returning the result. Thus, occasionally, a measurement takes longer than normal.

This extra time can cause problems in sweeps and other test sequences in which measurement timing is critical. To avoid the extra time for the reference measurements in these situations, you can select OFF. This setting disables the automatic reference measurements. Note that with automatic reference measurements disabled, the instrument may gradually drift out of specification.

To minimize the drift, make a reference and zero measurement immediately before a critical test sequence. You can use the ONCE setting to force a refresh of the reference and zero measurements used for the current aperture setting.

Autozero settings
Autozero setting	Description
OFF	Turns automatic reference measurements off.
ONCE	After immediately making one reference and one zero measurement, turns automatic reference measurements off.
AUTO	Automatically makes new acquisitions when the 2600B determines reference and zero values are out-of-date.

Setting autozero from the front panel

To change autozero from the front panel:

1. Press the CONFIG key.
2. Press the MEAS key.
3. Turn the navigation wheel to select AUTO-ZERO, and then press the ENTER key or the navigation wheel.
4. Turn the navigation wheel to select the mode (OFF, ONCE, or AUTO), and then press the ENTER key or the navigation wheel.
5. Press the EXIT (LOCAL) key to return to the previous display.

Setting autozero from a remote interface

To set autozero from a remote interface:

Use the autozero command with the appropriate option shown in the following table to set autozero through a remote interface (see smuX.measure.autozero). For example, send the following command to activate channel A automatic reference measurements:

smua.measure.autozero = smua.AUTOZERO_AUTO

Autozero command and options
Command*	Description
smuX.measure.autozero = smuX.AUTOZERO_OFF	Disable autozero. Old NPLC cache values are used when autozero is disabled (see NPLC caching).
smuX.measure.autozero = smuX.AUTOZERO_ONCE	After immediately making one reference and one zero measurement, turns automatic reference measurements off.
smuX.measure.autozero = smuX.AUTOZERO_AUTO	Automatically makes new reference and zero measurements when the 2600B determines values are out-of-date.
* smuX can be smua for channel A or smub for channel B

NPLC caching

NPLC caching speeds up operation by caching A/D reference and zero values for up to the ten most recent measurement aperture settings. Whenever the integration rate is changed using the SPEED key, or a user setup is recalled, the NPLC cache is checked. If the integration rate is already stored in the cache, the stored reference and zero values are recalled and used. If the integration rate is not already stored in the cache, a reference and zero value is acquired and stored in the cache when the next measurement is made. If there are already ten NPLC values stored, the oldest one is overwritten by the newest one. When autozero is off, NPLC values stored in the cache are used, regardless of age.

Requesting readings

You can request readings by including the appropriate measurement command as the argument for the print() command. The following programming example illustrates how to request a channel A current reading:

print(smua.measure.i())

Source-measure programming example

The following SMU programming example illustrates the setup and command sequence of a basic source‑measure procedure with the following parameters:

• Source function and range: Voltage, autorange
• Source output level: 5 V
• Current compliance limit: 10 mA
• Measure function and range: Current, 10 mA

-- Restore 2600B defaults.

smua.reset()

-- Select voltage source function.

smua.source.func = smua.OUTPUT_DCVOLTS

-- Set source range to autorange.

smua.source.autorangev = smua.AUTORANGE_ON

-- Set voltage source to 5 V.

smua.source.levelv = 5

-- Set current limit to 10 mA.

smua.source.limiti = 10e-3

-- Set current range to 10 mA.

smua.measure.rangei = 10e-3

-- Turn on output.

smua.source.output = smua.OUTPUT_ON

-- Print and place the current reading in the reading buffer.

print(smua.measure.i(smua.nvbuffer1))

-- Turn off output.

smua.source.output = smua.OUTPUT_OFF

Front-panel triggering example

This example uses the front panel to configure the trigger parameters to meet the following requirements:

• Manual triggering (TRIG key)
• Infinite trigger count (cycle indefinitely through measurement cycles)
• Interval (time between measurements): 1 s
• Delay (time from trigger to measurement): 2 s

To configure the trigger parameters:

1. Press the CONFIG key, and then the TRIG key.
2. Select TRIGGER-IN, and then press the ENTER key or the navigation wheel.
3. Select MANUAL, and then press the ENTER key or the navigation wheel.
4. Select COUNT, then select INFINITE, and then press the ENTER key or the navigation wheel.
5. Select INTERVAL, set the interval to 1 s, and then press the ENTER key or the navigation wheel.
6. Choose DELAY, set the delay to 2 s, and then press the ENTER key or the navigation wheel.
7. Use the EXIT (LOCAL) key to return to the normal display.
8. Press the OUTPUT ON/OFF control to turn the output on.
9. Press the TRIG key. A 2 s delay occurs before the first measurement. The instrument cycles through measurements indefinitely with a 1 s interval between measurements.
10. Press the OUTPUT ON/OFF control again to stop making readings.

Ohms ranging

The front‑panel ohms function does not use ranging. The instrument formats a calculated resistance reading (V/I) to best fit the display. There may be leading zeros if the ohms reading is less than 1 mO.

Basic ohms measurement procedure

When you use the MODE key to select ohms measurement, the 2600B is automatically configured as a current source with a level of 1 mA. To change the source function, source value, or compliance value (in other words, customize the standard ohmmeter configuration of the MODE key), then use the following steps to make ohms measurements. The following procedure assumes that the 2600B is already connected to the device under test (see “DUT test connections” in the Series 2600B User's Manual).

The following procedure requires dual-channel instruments (2602B, 2604B, 2612B, 2614B, 2634B, and 2636B) to be placed in single-channel display mode. For these models, press the DISPLAY key to select single-channel display mode. See “Display mode” in the Series 2600B User's Manual.

To make an ohms measurement:

1. Press the SRC key to select the source function.
2. Set the output source, as indicated by the units in the source field on the display. The flashing digit (cursor) indicates which value is presently selected for editing.
3. Move the cursor to the digit to change, then press the navigation wheel to enter the EDIT mode.
4. Use the RANGE keys to select a range that accommodates the value you want to set. For best accuracy, use the lowest possible source range.
5. Enter the source value.
6. Press the ENTER key or the navigation wheel to complete editing
7. Press the LIMIT key to edit the voltage or current limit. When programming a voltage limit, set the voltage limit above the maximum expected voltage across the resistor under test. When programming a current limit, set the current limit at or above the maximum expected current through the resistor under test.
8. Move the cursor to the digit to change, then press the navigation wheel to enter the EDIT mode, as indicated by the EDIT indicator.
9. Enter the limit value, then press the ENTER key or the navigation wheel to complete editing.
10. Press the MEAS key to display voltage or current.
11. Make sure that AUTO measurement range is on (press the AUTO key if needed).
12. Press the MEAS key as many times as needed to display ohms.
13. Press the OUTPUT ON/OFF control to turn the output on.
14. View the displayed reading (press the TRIG key if necessary). When finished, press the OUTPUT ON/OFF control to turn the output off.

Remote ohms command

Use the smuX.measure.r() function to get a resistance reading.

The programming example below illustrates how to get a resistance reading from SMU A:

reading = smua.measure.r()

See Remote source-measure commands for more commands to set up source and measure functions, and Introduction to TSP operation for more details.

Ohms programming example

The following programming example illustrates the setup and command sequence of a typical ohms measurement procedure with the following parameters:

• Source function: Current, 10 mA range, 10 mA output
• Voltage measure range: Autorange
• Voltage compliance: 10 V
• Sense mode: 4‑wire

-- Restore 2600B defaults.

smua.reset()

-- Select the current source function.

smua.source.func = smua.OUTPUT_DCAMPS

-- Set the source range to 10 mA.

smua.source.rangei = 10e-3

-- Set the current source to 10 mA.

smua.source.leveli = 10e-3

-- Set the voltage limit to 10 V.

smua.source.limitv = 10

-- Enable 4-wire ohms.

smua.sense = smua.SENSE_REMOTE

-- Set the voltage range to auto.

smua.measure.autorangev = smua.AUTORANGE_ON

-- Turn on output.

smua.source.output = smua.OUTPUT_ON

-- Retrieve a resistance reading.

print(smua.measure.r())

-- Turn off output.

smua.source.output = smua.OUTPUT_OFF

Ohms sensing

Ohms measurements can be made using either 2-wire or 4-wire sensing. See “DUT test connections” in the Series 2600B User's Manual for information on connections and sensing methods.

The 2-wire sensing method has the advantage of requiring only two test leads. However, as shown in the following figure (2-wire resistance sensing), test lead resistance can seriously affect the accuracy of 2-wire resistance measurements, particularly with lower resistance values.

The 4-wire sensing method, as shown in the following figure (4-wire resistance sensing), minimizes or eliminates the effects of lead resistance by measuring the voltage across the resistor under test with a second set of test leads. Because of the high input impedance of the voltmeter, the current through the sense leads is negligible, and the measured voltage is essentially the same as the voltage across the resistor under test.

Basic power measurement procedure

If you need to customize the standard wattmeter configuration of the MODE key, perform the following steps to make power measurements. The following procedure assumes that the 2600B is already connected to the device under test (DUT) as explained in “DUT test connections” in the Series 2600B User's Manual.

Hazardous voltages may be present on all output and guard terminals. To prevent electrical shock that could cause injury or death, never make or break connections to the 2600B while the output is on. Turn off the equipment from the front panel or disconnect the main power cord from the rear of the 2600B before handling cables. Putting the equipment into an output‑off state does not guarantee that the outputs are powered off if a hardware or software fault occurs.

To perform power measurements from the front panel:

1. If the instrument has two channels (2602B, 2604B, 2612B, 2614B, 2634B, and 2636B), press the DISPLAY key to place it in single-channel display mode.
2. Set source function and value. Press the SRC key to select the voltage or current source function, as required.
3. Set the output voltage or current to an appropriate value.
4. Move the cursor to the digit to change, then press the navigation wheel to enter the EDIT mode.
5. Use the RANGE keys to select a range that accommodates the value you want to set. For best accuracy, use the lowest possible source range.
6. Enter the source value.
7. Press the ENTER key or the navigation wheel to complete editing.
8. Press the LIMIT key and set the voltage or current limit high enough for the expected voltage or current across the DUT to be measured.
9. Press the LIMIT key.
10. Move the cursor to the digit to change, then press the navigation wheel to enter the EDIT mode, as indicated by the EDIT indicator.
11. Enter the limit value, then press the ENTER key or the navigation wheel to complete editing.
12. Press the MEAS key as many times as needed to display power.
13. Press the OUTPUT ON/OFF control to turn the output on.
14. View the displayed reading (press the TRIG key if necessary).
15. When finished, press the OUTPUT ON/OFF control again to turn the output off.

Power measurements using the remote interface

The following paragraphs summarize basic power measurement commands using the remote interface and also give a programming example for a typical power measurement situation.

Remote power reading command

The programming example below illustrates how to get a power reading from SMU A:

reading = smua.measure.p()

See Remote source-measure commands for more commands necessary to set up source and measure functions and also Introduction to TSP operation.

Power measurement programming example

The following programming example illustrates the setup and command sequence for a typical power measurement procedure with the following parameters:

• Source function: Voltage, source autorange, 5 V output
• Current measure function and range: Current, autorange
• Current compliance: 50 mA

-- Restore 2600B defaults.

smua.reset()

-- Select voltage source function.

smua.source.func = smua.OUTPUT_DCVOLTS

-- Enable source autoranging.

smua.source.autorangev = smua.AUTORANGE_ON

-- Set voltage source to 5 V.

smua.source.levelv = 5

-- Set current limit to 50 mA.

smua.source.limiti = 50e-3

-- Set current range to autorange.

smua.measure.autorangei = smua.AUTORANGE_ON

-- Turn on the output.

smua.source.output = smua.OUTPUT_ON

-- Retrieve a power reading.

print(smua.measure.p())

-- Turn off the output.

smua.source.output = smua.OUTPUT_OFF

Contact check commands

The following table summarizes the contact check commands. For a more complete description of these commands, refer to the “TSP command reference” section of the Series 2600B Reference Manual.

Basic contact check commands
Command	Description
flag = smuX.contact.check()	Determine if contact resistance is lower than threshold.
rhi, rlo = smuX.contact.r()	Measure the aggregate contact resistance.
smuX.contact.speed = speedSetting	Set speedSetting to one of the following: 0 or smuX.CONTACT_FAST 1 or smuX.CONTACT_MEDIUM 2 or smuX.CONTACT_SLOW
smuX.contact.threshold = rvalue	Set resistance threshold for the contact check function.

Contact check programming example

The following programming example illustrates the setup and command sequence for a typical contact check measurement. These commands set the contact check speed to fast and the threshold to 100 O. Then, a contact check measurement against the threshold is made. If it fails, a more accurate contact check measurement is made, and the test is aborted. If it does not fail, the output is turned on, and the test continues.

-- Restore defaults.

smua.reset()

-- Set contact-check speed to fast.

smua.contact.speed = smua.CONTACT_FAST

-- Set the contact-check threshold to 100 ohms.

smua.contact.threshold = 100

-- Check contacts against threshold.

if not smua.contact.check() then

-- Set speed to slow.

smua.contact.speed = smua.CONTACT_SLOW

-- Get aggregate resistance readings.

rhi, rlo = smua.contact.r()

-- Return contact resistances to the host.

print(rhi, rlo)

-- Terminate execution.

exit()

end

-- Turn output on and continue.

smua.source.output = smua.OUTPUT_ON

Pulse characteristics for the 2601B, 2602B, and 2604B

The following figure and table illustrate the pulse regions for each SMU. The programmed current and voltage levels for both SMUs must fall within the same pulse region. Refer to the 2600B specifications on tek.com/keithley for the latest pulse width and duty cycle information. Measurements are given priority over source and display operations, so make sure that the measurement time does not exceed the allowable pulse width and duty cycle in a particular pulse region.

Pulse region specification
Region (quadrant diagram)	Region maximum	Maximum pulse width	Maximum duty cycle
1	1 A at 40 V	DC, no limit	100%
1	3 A at 6 V	DC, no limit	100%
2	1.5 A at 40 V	100 ms	25%
3	5 A at 35 V	4 ms	4%
4	10 A at 20 V	1.8 ms	1%
5	5 A at 6 V	10 ms	10%

Pulse characteristics for the 2611B, 2612B, 2614B, 2634B, 2635B, and 2636B

The following figure and table illustrate the pulse regions for each SMU. The programmed current and voltage levels for both SMUs must fall within the same pulse region. Refer to the 2600B specifications on tek.com/keithley for the latest pulse width and duty cycle information. Measurements are given priority over source and display operations, so make sure that the measurement time does not exceed the allowable pulse width and duty cycle in a particular pulse region.

Pulse region specifications
Region (quadrant diagram)	Region maximum	Maximum pulse width	Maximum duty cycle
1	100 mA at 200 V	DC, no limit	100%
1	1.5 A at 20 V	DC, no limit	100%
2	1 A at 180 V	8.5 ms	1%
3	1 A at 200 V	2.2 ms	1%
4	10 A at 5 V	1 ms	2.2%

Guidelines for combining SMU outputs

When combining the outputs of two 2600B SMUs, restrict operation to pulse only or limited duty cycle operations whenever possible. DC operation in Region 1 is possible if necessary.

Do not place two voltage sources in parallel.

Do not place two current sources in series.

Carefully consider the appropriate output-off mode (smua.source.offmode) and output-off function (smua.source.offfunc) whenever changes are made to the source function. An alternative is to always use the high impedance output-off mode (smua.source.offmode = smua.OUTPUT_HIGH_Z).

To obtain the cleanest pulse edges and sweep steps, the rise and fall times of the individual SMUs must be similar. For comparable rise and fall times, the source range, source level, and limit range of SMU 1 should match the source range, source level, and limit range of SMU 2. Because you cannot set the source limit range directly, you must choose limit values that cause both SMUs to operate on the same limit range.

Additional configuration guidelines are presented in the following topics. Additional information, including examples of combining SMU instruments, is available in application notes on tek.com/keithley.

Source current using two 2600B instruments in parallel

This example shows the recommended approach for setting the source and limit ranges and levels when combining SMU current sources in parallel.

The values are based on the current and voltage levels available in Region 4 of a 2601B, 2602B, or 2604B SMU, as shown in the table in Combining SMU outputs. For information about generating pulses with a 2600B, refer to Using timers to perform pulse mode sweeps.

This configuration allows the combined SMUs to supply more current than a single SMU current source can provide. In this example, SMU 1 and SMU 2 each supply one-half of the total current for the SMU combination.

In this configuration, it is best practice to use only one SMU to limit the voltage output of the SMU combination. In this example, SMU 2 limits the voltage. A good approach for making sure that both SMUs are set to the same source limit range, which is recommended, is to set SMU 1 to the maximum voltage allowed in Region 4, then set the limit for SMU 2 ten percent lower.

A 10% source limit margin is generally recommended, but this value can be adjusted to meet the requirements of a specific application.

Configure two 2600B SMUs to get the maximum pulsed current level possible in Region 4:

20 A with 18 V source limit

SMU 1 configuration (sources one-half of the total pulse current):

Source function:

smua.source.func = smua.OUTPUT_DCAMPS

Source range:

smua.source.rangei = 10

Idle (bias) source level (source level at the base of pulse):

smua.source.leveli = 0

Idle (bias) source limit (source limit at base of pulse):

smua.source.limitv = 6

Pulse source level (source level at top of pulse):

smua.trigger.source.listi({10})

Pulse source limit. SMU 2 controls the source limit for the combined SMUs. Set the voltage source limit of SMU 1 to the maximum voltage allowed in Region 4:

smua.trigger.source.limitv = 20

Output-off mode:

smua.source.offmode = smua.OUTPUT_NORMAL

Output-off function:

smua.source.offfunc = smua.OUTPUT_DCAMPS

Normal output-off voltage limit:

smua.source.offlimitv = 20

SMU 2 configuration (sources one-half of the total pulse current):

Source function:

smua.source.func = smua.OUTPUT_DCAMPS

Source range:

smua.source.rangei = 10

Idle (bias) source level (source level at base of pulse):

smua.source.leveli = 0

Idle (bias) source limit (source limit at base of pulse). Set the SMU 2 idle source limit ten percent lower than the SMU 1 idle source limit:

smua.source.limitv = 5.4

Pulse source level (source level at top of pulse):

smua.trigger.source.listi({10})

Pulse source limit. SMU 2 controls the source limit for the combined SMUs. Set the voltage source limit of SMU 2 ten percent lower than the source limit of SMU 1:

smua.trigger.source.limitv = 18

Output-off mode:

smua.source.offmode = smua.OUTPUT_NORMAL

Output-off function:

smua.source.offfunc = smua.OUTPUT_DCVOLTS

Current limit for normal output-off mode (this is the maximum current that flows between the two SMUs when the output is off):

smua.source.offlimiti = 1e-3 -- default

Voltage compliance must be ten percent lower than the voltage compliance of SMU 1. This causes SMU 1 to control the maximum voltage across the DUT. Voltage compliance limit (maximum):

smua.trigger.source.limitv = 18

Source voltage using two 2600B instruments in series

This example shows the recommended approach for setting the source and limit ranges and levels when combining SMU voltage sources in series.

The following values are based on the current and voltage levels available in Region 4 of a 2601B, 2602B, or 2604B SMU, as shown in the table in Combining SMU outputs. For information about generating pulses with a 2600B, refer to Using timers to perform pulse mode sweeps.

This configuration supplies more voltage than a single SMU voltage source can provide. In this example, SMU 1 and SMU 2 each supply one-half of the total voltage for the SMU combination. For the back-to-back series connection shown, the total voltage of the combined SMUs is V _{SMU 2} - V_{SMU 1}. To obtain a net differential voltage that is twice V_SMU 2, the polarity of SMU 1 is set to the opposite of the polarity of SMU 2.

In this configuration, it is best practice to use only one SMU to limit the current output of the SMU combination. In this example, SMU 2 limits the current. A good approach for making sure that both SMUs are set to the same source limit range, which is recommended, is to set SMU 1 to the maximum current allowed in Region 4, then set the limit for SMU 2 ten percent lower.

A 10% source limit margin is generally recommended, but this value can be adjusted to meet the requirements of a specific application.

Configure two 2600B SMUs to get the maximum pulsed voltage level possible in Region 4:

40 V with 9 A source limit

SMU 1 configuration (sources one-half of the total pulse voltage):

Source function:

smua.source.func = smua.OUTPUT_DCVOLTS

Source range:

smua.source.rangev = 20

Idle (bias) source level (source level at base of pulse):

smua.source.levelv = -1e-12

Source polarity changes incur a 100 µs settling delay. Because the number 0 is treated as a positive value in the 2600B, negative-going pulses with a 0 V bias level require the source to change polarity. To ensure the proper pulse timing of SMU 1 and SMU 2, it is best to eliminate the SMU 1 polarity changes and avoid the associated 100 µs time penalty. The easiest way to do this is set the bias level to a negative value that is significantly less than the programming resolution of the instrument, such as -1e-12. Functionally, this value is the same as zero, but it is mathematically negative, which eliminates the polarity change.

Idle (bias) source limit (source limit at base of pulse):

smua.source.limiti = 1

Pulse source level (source level at top of pulse):

smua.trigger.source.listv({-20})

As explained in the note above, the polarity of SMU 1 is generally the opposite of the voltage polarity across the device. To achieve a positive voltage across the device, program SMU 1 to a negative voltage level. For example, to output 40 V across the device, program SMU 1 to -20 V and SMU 2 to +20 V. To achieve a negative voltage across the device, program SMU 1 to a positive voltage level and SMU 2 to a negative voltage level.

Pulse source limit. SMU 2 controls the source limit for the combined SMUs. Set the current source limit of SMU 1 to the maximum current allowed in Region 4:

smua.trigger.source.limiti = 10

Output-off mode:

smua.source.offmode = smua.OUTPUT_NORMAL

Output-off function:

smua.source.offfunc = smua.OUTPUT_DCVOLTS

Normal output-off current limit:

smua.source.offlimiti = 1e-3 --(default)

SMU 2 configuration (sources one-half of the total pulse voltage):

Source function:

smua.source.func = smua.OUTPUT_DCVOLTS

Source range:

smua.source.rangev = 20

Idle (bias) source level (source level at base of pulse):

smua.source.levelv = 0

Idle (bias) source limit (source limit at base of pulse). This is similar to the pulse source limit. Set the SMU 2 idle source limit ten percent lower than the SMU 1 limit:

smua.source.limiti = 0.9

Pulse source level (source level at top of pulse):

smua.trigger.source.listv({-20})

Pulse source limit. SMU 2 controls the source limit for the combined SMUs. Set the current source limit of SMU 2 ten percent lower than the source limit of SMU 1:

smua.trigger.source.limiti = 9

Output-off mode:

smua.source.offmode = smua.OUTPUT_NORMAL

Output-off function:

smua.source.offfunc = smua.OUTPUT_DCVOLTS

Normal output-off current limit (0.9 mA, which is 10% less than the SMU 1 output-off limit):

smua.source.offlimiti = 0.9e-3

Source voltage with extended current using two 2600B instruments in parallel

This example shows the recommended approach for setting the source and limit ranges and levels when combining a SMU voltage source in parallel with a SMU current source.

The values are based on the current and voltage levels available in Region 4 of a 2601B, 2602B, or 2604B SMU, as shown in the table in Combining SMU outputs. For information about generating pulses with a 2600B, refer to Using timers to perform pulse mode sweeps.

The purpose of this configuration is to supply more current than a single SMU voltage source can provide. In this example, SMU 2 controls the voltage applied to a device-under-test (DUT). At full power, SMU 1 supplies 47% of the current required by the load and SMU 2 supplies 53%. SMU2 sinks excess current from SMU 1 when DUT current draw is less than the maximum current of the SMU combination.

Proper operation of this configuration requires that SMU 1 does not limit the voltage from SMU 2 and that SMU 2 does not limit the current from SMU 1. To accomplish this:

• Set the voltage source level of SMU 2 ten percent lower than voltage source limit of SMU 1.
• Set the current source level of SMU 1 ten percent lower than the current source limit of SMU 2.
• Set the voltage source limit of SMU 1 to the maximum voltage allowed in Region 4.
• Set the current source limit of SMU 2 to the maximum current allowed in Region 4.

These settings ensure that both SMUs are set to the same source and limit ranges, as recommended.

A 10% source limit margin is generally recommended, but this value can be adjusted to meet the requirements of a specific application.

Configure two 2600B SMUs to obtain the maximum pulsed voltage level possible in Region 4:

18 V with 19 A capacity

SMU 1 configuration (supplies additional current that SMU 2 alone cannot provide):

Source function:

smua.source.func = smua.OUTPUT_DCAMPS

Source range:

smua.source.rangei = 10

Idle (bias) source level (source level at base of pulse):

smua.source.leveli = 0

Idle (bias) source limit (source limit at base of pulse):

smua.source.limitv = 6

Pulse source level (source level at top of pulse). Set the pulse source level ten percent lower than the current source limit of SMU 2:

smua.trigger.source.listi({9})

Pulse source limit. SMU 1 voltage source limit must be greater than the maximum voltage supplied by SMU 2. Set the voltage source limit of SMU 1 to the maximum voltage allowed in Region 4:

smua.trigger.source.limitv = 20

Output-off mode:

smua.source.offmode = smua.OUTPUT_NORMAL

Output-off function:

smua.source.offfunc = smua.OUTPUT_DCAMPS

Normal output-off voltage limit (40 V maximum):

smua.source.offlimitv = 20

SMU 2 configuration (SMU 2 controls the voltage applied to the device‑under‑test):

Source function:

smua.source.func = smua.OUTPUT_DCVOLTS

Source range:

smua.source.rangev = 20

Idle (bias) source level (source level at base of pulse):

smua.source.levelv = 0

Idle (bias) source limit (source limit at base of pulse):

smua.source.limiti = 1

Pulse source level (source level at top of pulse). Set the source level of SMU 2 ten percent lower than the voltage source limit of SMU 1:

smua.trigger.source.listv({18})

Pulse source limit. The pulse current source limit of SMU 2 must be greater than the maximum current supplied by SMU 1. Set the current source limit of SMU 2 to the maximum current level allowed in Region 4:

smua.trigger.source.limiti = 10

Output-off mode:

smua.source.offmode = smua.OUTPUT_NORMAL

Output-off function:

smua.source.offfunc = smua.OUTPUT_DCVOLTS

Normal output-off current limit:

smua.source.offlimiti = 1e-3

Combining channels in series to output higher voltage

Channels in series can cause hazardous voltage (>30 V_RMS, 42 V_PEAK) to be present and accessible at the 2600B output connector. A safety shield must be used whenever hazardous voltages will be present in the test circuit. To prevent electrical shock that could cause injury or death, never use the 2600B in a test circuit that may contain hazardous voltages without a properly installed and configured safety shield.

When combining two 2600B SMU voltage sources in series, it is possible for the SMU combination to output hazardous voltage levels even though the individual SMUs cannot.

The following figure illustrates a Model 2602B configured with the two channels connected in series to output up to 80 V (40 V per channel).

Whenever hazardous voltage (>30 V_RMS, 42 V _PEAK) is output, a safety shield must completely surround the DUT test circuit. When using a metal safety shield, it must be connected to a known protective earth (safety ground) and chassis ground.

(1) 2602B Channel A: SMU maximum pulse voltage: +40 V
(2) 2602B Channel B: SMU maximum pulse voltage: -40 V
(3) Series SMU maximum pulse voltage (as shown): 80 V

Combining channels in parallel to output higher current

Higher pulse current can be output by connecting two 2600B instrument channels in parallel.

The figure below illustrates the connection scheme of two Model 2602B channels connected in parallel. Two Model 2602B channels can output up to 20 A at 18 V (see Combining SMU outputs). The current delivered to the device under test (DUT) is the sum of the currents output by SMU channels (I_T). Combining the two 2600B instrument channels expands the power envelope.

I₁ Single SMU maximum pulse current: 10 A
I₂ Single SMU maximum pulse current: 10 A
I_T Paralleled SMU channels maximum pulse current (as shown): 20 A

Normal output-off mode

The normal output‑off mode is the default output‑off mode setting. When the source‑measure unit (SMU) is in the normal output‑off mode, you can select either the current or the voltage output‑off function (see Output-off function). You can also specify current and voltage output‑off limits (Output-off limits (compliance)).

When the output is turned off, the output goes to either 0 V or 0 A, depending on the selected output‑off function. Voltage is the default output‑off function.

High-impedance output-off mode

For the high-impedance output-off mode (HI‑Z), the output relay opens when the output is turned off. This disconnects external circuitry from the input and output of the source‑measure unit (SMU). To prevent excessive wear on the output relay, do not use this output-off mode for tests that turn the output off and on frequently.

Zero output-off mode

When the zero output‑off mode is selected, the programmed source remains on the display, but internally, the voltage source is selected and is set to 0 V. Measurements are made and displayed.

When the selected source is voltage, the current compliance setting remains the same as the output‑on value and compliance detection remains active.

When the selected source is current, the current compliance setting is the programmed current source value or 10 percent full-scale of the present current range, whichever is greater.

You can use the 2600B as a current meter when it is in zero output‑off mode because it outputs 0 V but measures current.

To configure the output-off mode from the front panel:

1. Press the CONFIG key.
2. Press the OUTPUT ON/OFF control.
3. Select OFF-STATE.
4. Select MODE.
5. Select the output-off mode: HI-Z (high‑impedance), NORMAL, or ZERO.
6. Press the EXIT key to return to the normal display.

To select the normal output-off mode over a remote interface:*

smua.source.offmode = smua.OUTPUT_NORMAL

To select the high-impedance output-off mode over a remote interface:*

smua.source.offmode = smua.OUTPUT_HIGH_Z

To select the zero output-off mode over a remote interface:*

smua.source.offmode = smua.OUTPUT_ZERO

* smuX can be smua for channel A or smub for channel B

Output-off function

This setting is used only when the output is turned off and the 2600B is set to the normal output‑off mode (smuX.source.offmode = smu X.OUTPUT_NORMAL).

You can set the output-off function to CURRENT or VOLTAGE through the CONFIG menu on the front panel, or by using the smuX.source.offfunc attribute from a remote interface. VOLTAGE is the default output‑off function.

When the output is turned off and the selected output‑off function is VOLTAGE ( smuX.source.offfunc = smuX.OUTPUT_DCVOLTS):

• The source‑measure unit (SMU) sources 0 V.
• The current limit is set by the smuX.source.offlimiti attribute (default 1 mA).

When the output is turned off and the selected output‑off function is CURRENT ( smuX.source.offfunc = smuX.OUTPUT_DCAMPS):

• The SMU sources 0 A.
• The voltage limit is set by the smuX.source.offlimitv attribute (default 40 V).

When the output-off function is set to either voltage or current, the SMU may source or sink a very small amount of power. In most cases, this source or sink power level is insignificant.

Selecting the output-off function

NOTE This setting is used only when the output is turned off and the source‑measure unit (SMU) is in NORMAL output‑off mode.

To configure the output-off function from the front panel:

1. Press the CONFIG key.
2. Press the OUTPUT ON/OFF control.
3. Select OFF-STATE and then select FUNCTION.
4. Select CURRENT or VOLTAGE.
5. Press the EXIT key to return to the normal display.

To configure the output-off function remotely:

To set 0 V output with current limit set by the smuX.source.offlimiti attribute:*

smuX.source.offfunc = smuX.OUTPUT_DCVOLTS

To set 0 A output with voltage limit set by the smuX.source.offlimitv attribute:*

smuX.source.offfunc = smuX.OUTPUT_DCAMPS

* smuX can be smua for channel A or smub for channel B

Output-off limits (compliance)

You can set output-off limits (compliance) for the current and voltage output‑off functions using the CONFIG menu on the 2600B front panel, or by setting the smuX .source.offlimitY attribute from a remote interface. The output‑off limits only apply when the output-off mode is normal.

Setting output-off limits

Setting the output‑off limit for CURRENT (smuX.source.offlimiti) specifies the current limit for the voltage source; setting the output‑off limit for VOLTAGE (smuX.source.offlimitv) specifies the voltage limit for the current source.

To configure the output-off limits from the front panel:

1. Press the CONFIG key.
2. Press the OUTPUT ON/OFF control.
3. Select OFF-STATE and then select LIMIT.
4. Select CURRENT or VOLTAGE.
5. Set the limit value and then press the ENTER key or the navigation wheel.
6. Press the EXIT key to return to the normal display.

To set the current limit in NORMAL output‑off mode remotely:*

smuX.source.offlimiti = iValue

To set the voltage limit in NORMAL output‑off mode remotely:*

smuX.source.offlimitv = vValue

* smuX can be smua for channel A or smub for channel B

Remote programming output-off states quick reference

The content of the following table is a quick reference of commands for programming output-off states from a remote interface.

Output-off state programming quick reference
Command*	Description
smuX.source.offmode = smua.OUTPUT_NORMAL	Selects normal output‑off mode.
smuX.source.offmode = smua.OUTPUT_HIGH_Z	Selects high‑impedance output‑off mode.
smuX.source.offmode = smua.OUTPUT_ZERO	Selects zero output-off mode.
smuX.source.offfunc = smua.OUTPUT_DCVOLTS	Sets 0 V output with current limit specified by the smua.source.offlimiti attribute.
smuX.source.offfunc = smua.OUTPUT_DCAMPS	Sets 0 A output with voltage limit specified by the smua.source.offlimitv attribute.
smuX.source.offlimiti = iValue	Sets current limit in normal output‑off mode.
smuX.source.offlimitv = vValue	Sets voltage limit in normal output‑off mode.
* smuX can be smua for channel A or smub for channel B

Available ranges

The following table lists the available source and measurement ranges for the 2600B.

2601B, 2602B, or 2604B		2611B, 2612B, or 2614B		2634B, 2635B, or 2636B
Voltage ranges	Current ranges	Voltage ranges	Current ranges	Voltage ranges	Current ranges
100 mV	100 nA	200 mV	100 nA	200 mV	100 pA2,3
1 V	1 µA	2 V	1 µA	2 V	1 nA
6 V	10 µA	20 V	10 µA	20 V	10 nA
40 V	100 µA	200 V	100 µA	200 V	100 nA
	1 mA		1 mA		1 µA
	10 mA		10 mA		10 µA
	100 mA		100 mA		100 µA
	1 A		1 A		1 mA
	3 A		1.5 A		10 mA
			10 A1		100 mA
					1 A
					1.5 A
1. The 10 A range is only available in pulse mode. 2. The 100 pA range is only for measurements. 3. The 100 pA measurement range is not available on the 2634B.

Maximum source values and readings

The full-scale output for each voltage and current source range is 101 percent of the selected range, but the full-scale measurement is 102 percent of the range. For example, ±1.01 A is the full-scale source value for the 1 A range, and ±102 mA is the full-scale reading for the 100 mA measurement range. Input levels that exceed the maximum levels cause the overflow message to be displayed. The instrument autoranges at 100 percent of the range.

Measure autodelay

The measure delay is a specific delay that is applied before each measurement is made. This delay is disabled by default (measurements are made immediately). You can change the default delay by setting the smuX.measure.delay attribute either to a specific value or to an autodelay setting (set smu X.measure.delay = smuX.DELAY_AUTO). If the measure delay is set to the autodelay setting, a range-dependent delay is applied each time the instrument performs a current measurement. This delay also happens for the measurement that is made after changing current ranges during an autoranged measurement. The default measurement delay varies by model.

You can increase or decrease the autodelay by changing the delay factor (for example, to reduce the delay across all ranges by half, set smuX.measure.delayfactor = 0.5). For additional information, refer to smuX.measure.delayfactor.

Ranging limitations

If the source and measure functions are different (such as source V and measure I, or source I and measure V), you can set source and measure ranges separately. If both the source and the measure functions are the same, the measure range is locked to the source range. In addition, there are other limitations.

• 2601B, 2602B, 2604B: With the 40 V V‑Source range selected, the highest current measurement range is 1 A. With the 3 A I‑Source range selected, the highest voltage measurement range is 6 V. Refer to Operating boundaries for power derating information.
• 2611B, 2612B, 2614B, 2634B, 2635B, 2636B: With the 200 V V-Source range selected, the highest current measurement range is 100 mA. With I-Source ranges above 100 mA selected, the highest voltage measurement range is 20 V. Refer to Operating boundaries for power derating information.

Manual ranging

Use the range keys, and , to select a fixed range:

• To set the source range, press the SRC key, and then use the RANGE keys to set the range.
• To set the measure range, select the single-channel display mode (2602B, 2604B, 2612B, 2614B, 2634B, or 2636B), and then use the RANGE keys to set the range.

If the instrument displays the overflow message on a particular range, select a higher range until an on-range reading is displayed. To ensure the best accuracy and resolution, use the lowest range possible that does not cause an overflow.

Autoranging

To use automatic source ranging, press SRC then the AUTO range key.

To use automatic measure ranging, press the MEAS key followed by the AUTO range key. The AUTO indicator turns on when source or measure autoranging is selected.

When autorange is selected, the instrument automatically sets the best range to source or measure the applied signal. The instrument increases the range to 100 percent of the present range.

When you change a source value, source autoranging is automatically turned off and remains off until you re‑enable it.

Low range limits

The low range limit sets the lowest range that the 2600B uses when autoranging is enabled. This feature is useful for minimizing autorange settling times when measurements require numerous range changes.

To individually set low range limits for Source V, Source I, Measure V, and Measure I:

1. Press the CONFIG key, then press either the SRC key (for source) or the MEAS key (for measure).
2. Select voltage or current source, or measure, as appropriate, and then press the ENTER key or the navigation wheel.
3. Select LOWRANGE, and then press the ENTER key or the navigation wheel.
4. Set the low range to the appropriate setting, and then press the ENTER key or the navigation wheel.
5. Press the EXIT (LOCAL) key twice to return to the main display.

Range considerations

The source range and measure range settings can interact depending on the source function. Additionally, the output state (on or off) can affect how the range is set. The following table describes these interactions.

If...	Then...	Notes
The source function is the same as the measurement function (for example, sourcing voltage and measuring voltage)	The measurement range is locked to be the same as the source range.	The setting for the voltage measure range is retained and used when the source function is changed to current. 2600B example: smua.source.func = smua.OUTPUT_DCVOLTS smua.source.rangev = 1 smua.measure.rangev = 10 -- Prints 1, the source range print(smua.measure.rangev) smua.source.func = smua.OUTPUT_DCAMPS -- Prints 10, the measure range print(smua.measure.rangev)
A source or measurement range for a function is explicitly set	Autoranging for that function is disabled.	Autoranging is controlled separately for each source and measurement function: Source voltage, source current, measure voltage, and measure current. Autoranging is enabled for all measurement functions by default.
Source autoranging is enabled	The output level controls the range.	Querying the range after the level is set returns the range the instrument chose as appropriate.

You send a source level that is out of range while autorange is off	The instrument does not return an error until the output is turned on.	While the output is turned off, the display shows a series of question marks. For example, ???.???mA is displayed for the 100 mA range. The display also shows a series of question marks when pulsing in the extended operating area on the 10 A range.
Measure autoranging is enabled	The measure range changes only when a measurement is made.	Querying the range after the measurement is made returns the range that the instrument chose.

Range programming

Range commands

The following tables summarize commands necessary to control measure and source ranges. See the TSP command reference for more details about these commands.

Measure range commands*
Command**	Description
smuX.measure.autorangei = smuX.AUTORANGE_ON	Enable current measure autorange.
smuX.measure.autorangei = smuX.AUTORANGE_OFF	Disable current measure autorange.
smuX.measure.autorangev = smuX.AUTORANGE_ON	Enable voltage measure autorange.
smuX.measure.autorangev = smuX.AUTORANGE_OFF	Disable voltage measure autorange.
smuX.measure.lowrangei = lowrange	Set lowest current measure range for autorange.
smuX.measure.lowrangev = lowrange	Set lowest voltage measure range for autorange.
smuX.measure.rangei = rangeval	Select manual current measure range.
smuX.measure.rangev = rangeval	Select manual voltage measure range.
* See Available ranges ** smuX can be smua for channel A or smub for channel B

Source range and limit commands*
Command**	Description
smuX.source.autorangei = smuX.AUTORANGE_ON	Enable current source autorange.
smuX.source.autorangei = smuX.AUTORANGE_OFF	Disable current source autorange.
smuX.source.autorangev = smuX.AUTORANGE_ON	Enable voltage source autorange.
smuX.source.autorangev = smuX.AUTORANGE_OFF	Disable voltage source autorange.
smuX.source.limiti = level	Set voltage source current limit (compliance).
smuX.source.limitv = level	Set current source voltage limit (compliance).
smuX.source.limitp = level	Set source power limit (compliance).
smuX.source.lowrangei = lowrange	Set lowest current source range for autorange.
smuX.source.lowrangev = lowrange	Set lowest voltage source range for autorange.
smuX.source.rangei = rangeval	Select manual current source range.
smuX.source.rangev = rangeval	Select manual voltage source range.
* See Available ranges ** smuX can be smua for channel A or smub for channel B

Range programming example

The programming example below illustrates how to control both source and measure ranges. The 2600B is set up as follows:

• Voltage source range: Autorange
• Current measure range: 10 mA
• Voltage source current limit: 10 mA

-- Restore 2600B defaults.

smua.reset()

-- Set V source range to autorange.

smua.source.autorangev = smua.AUTORANGE_ON

-- Select 10 mA measure range.

smua.measure.rangei = 10e-3

-- Set limit level to 10 mA.

smua.source.limiti = 10e-3

Setting display resolution from the front panel

To set the display resolution, press the DIGITS key until the correct number of digits is displayed. Available display resolutions are 4.5, 5.5, and 6.5 digits.

For 2602B, 2604B, 2612B, 2614B, 2634B, and 2636B when they are in dual-channel display mode, the maximum display resolution is 4.5 digits. Pressing the DIGITS key displays a message that advises you to change the display to the indicated channel. This message is also displayed in single-channel display mode when you press the DIGITS key for the channel that is not being displayed.

Setting display resolution from a remote interface

The following table summarizes use of the display.smuX.digits command. See the TSP command reference for more information.

Digits commands
Command*	Description
display.smuX.digits = display.DIGITS_4_5	Set the display to 4.5 digits.
display.smuX.digits = display.DIGITS_5_5	Set the display to 5.5 digits.
display.smuX.digits = display.DIGITS_6_5	Set the display to 6.5 digits.
* smuX can be smua for channel A or smub for channel B

Digits programming example

-- Select 5.5 digits.

display.smua.digits = display.DIGITS_5_5

Setting the speed from the front panel

Press the SPEED key (or use the CONFIG menu) to display the following menu items:

• FAST: Sets the measurement speed to 0.01 PLC (fast performance, but accuracy is reduced).
• MED: Sets the measurement speed to 0.10 PLC (speed and accuracy are balanced).
• NORMAL: Sets the measurement speed to 1.00 PLC (speed and accuracy are balanced).
• HI-ACCURACY: Sets the measurement speed to 10.00 PLC (high accuracy, but speed is reduced).
• OTHER: Sets the measurement speed to any value from 0.001 PLC to 25 PLC.

Setting the speed using the remote interface

The following table shows the command that controls speed. See the TSP command reference for more information.

Speed command
Command*	Description
smuX.measure.nplc = nplc	Sets the speed of the A/D converter (nplc = 0.001 to 25).
* smuX can be smua for channel A or smub for channel B

Speed programming example

Use the NPLC command to set the speed of the integrating analog-to-digital converter (ADC). The programming example below illustrates how to set the speed to 10 PLC:

-- Set NPLC to 10.

smua.measure.nplc = 10

Sweep characteristics

For any of the sweep types, program a pulse sweep by configuring the end pulse action. Refer to Pulse mode sweeps for more information.

Linear staircase sweeps

As shown below, this sweep type steps from a start voltage or current value to an ending (stop) value. When enabled, a measurement is made at each point after the source and measurement settling time.

A linear staircase sweep is configured using a start level, a stop level, and the total number of points, including the start and stop points. The step size is determined by the start and stop levels, and the number of sweep points:

step = (stop - start) / (points - 1)

The number of sweep steps actually performed is determined by the trigger count. Refer to Triggering for more information.

The sweep can be either positive-going or negative-going, depending on the relative values of the start and stop parameters. When the sweep starts, the output goes to the start source level. The output then changes in equal steps until the stop level is reached. If the trigger count is greater than the number of points specified, the SMU starts over at the beginning value.

To configure a linear staircase sweep, use the smuX.trigger.source.linearY() command. This function configures the source values the SMU outputs when performing a linear sweep. After configuring the sweep, you must also enable the source action by setting the following attribute:*

smuX.trigger.source.action

* smuX can be smua for channel A or smub for channel B

Example:

-- Configure a sweep from 0 to 10 V in 1 V steps.

smua.trigger.source.linearv(0, 10, 11)

-- Enable the source action.

smua.trigger.source.action = smua.ENABLE

For more information, see smuX.trigger.source.linearY().

Logarithmic staircase sweeps

This type of sweep is similar to the linear staircase sweep. The steps, however, are done on a logarithmic scale.

Like a linear staircase sweep, logarithmic sweeps are configured using a start level, a stop level, and the number of points. The step size is determined by the start and stop levels, and the number of sweep points. However, in a logarithmic sweep, the step size increases or decreases exponentially. To create an increasing logarithmic sweep, set the stop value to be greater than the start value. To create a decreasing logarithmic sweep, set the stop value to be less than the start value. When enabled, a measurement is made at each step after source and measurement settling time. An asymptote can also be used to control the inflection of a sweep.

The number of sweep steps actually performed is determined by the trigger count. See Triggering for more information.

The formula for a logarithmic sweep is:

v_i = A + kbⁱ

Where:

vi	=	The source value at source point i
i	=	The index of points in the sweep (ranges from 0 to N - 1), where N is the number of points in the sweep
k	=	The initial source value as an offset from the asymptote
b	=	The step size ratio
A	=	The asymptote value

The asymptote is used to change the inflection of the sweep curve and allow it to sweep through zero. The following figures depict the effect of the asymptote on the inflection of the sweep curve.

Solving for k and b provides the following formulas:

Where:

Vend	= The source value at the end point
Vstart	= The source value at the start point
N	= The number of points in the sweep
A	= The asymptote value

The number of points in a sweep is one greater than the number of steps in the sweep.

The following figure is an example of a five-point logarithmic sweep from 1 V to 10 V.

In this example:

A = 0, V_start = 1, V_end = 10, N = 5

Using the formula above, k = 1

Step size (b) for the sweep in the above figure is calculated as follows:

Therefore, b = 10^{(log step size)} = 1.7783

The log steps for this sweep are listed in the table below.

Logarithmic sweep points
Source point (N)	Source level (V)	Step number (i)
1	1	0
2	1.7783	1
3	3.1623	2
4	5.6234	3
5	10	4

When this sweep starts, the output goes to the start level (1 V) and sweeps through the symmetrical log points.

To configure a logarithmic staircase sweep, use the smuX.trigger.source.logY()function. This function configures the source values the source-measure unit (SMU) outputs when performing a logarithmic sweep. After configuring the sweep, you must also enable the source action by setting the smu X.trigger.source.action attribute.

Example:

-- Configure a sweep from 1 to 10 V in 10 steps with an asymptote of 0 V.

smua.trigger.source.logv(1, 10, 11, 0)

-- Enable the source action.

smua.trigger.source.action = smua.ENABLE

For more information, see smuX.trigger.source.logY().

List sweeps

Use a list sweep to configure a sweep with arbitrary steps. When enabled, a measurement is made at each point after source and measurement settling time.

To configure a list sweep, use the smuX.trigger.source.listY()function. This function configures the source values that the source‑measure unit (SMU) outputs when performing a list sweep. After configuring the sweep, you must also enable the source action by setting the smu X.trigger.source.action attribute.

Example:

-- Sweep through 3 V, 1 V, 4 V, 5 V, and 2 V.

smua.trigger.source.listv({3, 1, 4, 5, 2})

-- Enable the source action.

smua.trigger.source.action = smua.ENABLE

When the sweep is started, the output level goes to the first point in the sweep. The sweep continues through the steps in the order that they were programmed.

The following figure shows a different example of a list sweep with six measurement points. When the sweep starts, the current or voltage goes to the first point in the sweep. The instrument cycles through the sweep points in the programmed order.

Pulse mode sweeps

To create a pulse sweep for any of the sweep types, configure the end pulse action.

To configure a pulse sweep for source‑measure unit (SMU) A, send:

smua.trigger.endpulse.action = smua.SOURCE_IDLE

To configure a DC sweep for SMU A, send:

smua.trigger.endpulse.action = smua.SOURCE_HOLD

Timers must be used to configure the pulse width and period. Refer to Using timers to perform pulsed sweeps for details.

The pulse width is managed by controlling the duration between the source stimulus event and the end pulse stimulus event. A latency exists between these stimulus events and their resulting source level transitions. This trigger latency can vary based on factors such as the source range and the electrical characteristics of the device under test (DUT).

The figure below shows the source and end pulse stimulus events in relationship to the pulse (see Triggering for information on stimulus events). Any change in ?t results in a corresponding change in the pulse width.

Pulse duty cycle

Duty cycle is the percentage of time during the pulse period that the output is on. It is calculated as follows:

Duty cycle = Pulse width / (Pulse width + Off time)

For example, if the pulse width is 10 ms and the off time is 90 ms, the duty cycle is calculated as follows:

Duty cycle	= 10 ms / (10 ms + 90 ms)
	= 10 ms / 100 ms
	= 0.10
	= 10 percent

See Maximum duty cycle equation for additional information on calculating the maximum duty cycle for a SMU.

Pulsing in the extended operating area

Pulse sweeps can be performed outside of the standard operating area by setting the appropriate compliance level. Review the specifications for the 2600B to determine the maximum current and voltage values available in pulse mode. When pulsing in the extended operating area, the source‑measure unit (SMU) forces the pulse to end early if the pulse width exceeds the maximum value. It also delays the next source action as necessary to stay within the duty cycle capabilities of the SMU. The following figure and table illustrate the pulse regions for a SMU when pulsing in the extended operating area. Refer to the 2600B specifications on tek.com/keithley for the latest pulse width and duty cycle information.

Pulse region specification
Region (quadrant diagram)	Region maximum	Maximum pulse width	Maximum duty cycle
1	1 A at 40 V	DC, no limit	100%
1	3 A at 6 V	DC, no limit	100%
2	1.5 A at 40 V	100 ms	25%
3	5 A at 35 V	4 ms	4%
4	10 A at 20 V	1.8 ms	1%
5	5 A at 6 V	10 ms	10%

Configuring and running sweeps

Use the following topics to configure and run a sweep.

Configuring compliance limits remotely

You can configure voltage and current limits using the smuX.trigger.source.limitY attribute, which sets the sweep source limits. For example, to set the SMU A sweep limit to 10 V, send the command:

smua.trigger.source.limitv = 10

Configuring end sweep actions remotely

Use the end sweep action to configure the source action at the end of the sweep. You can program the source‑measure unit (SMU) to return to the idle source level or hold the last value of the sweep. Configure the end sweep action by setting the smuX.trigger.endsweep.action attribute. For example, execute the following command to configure SMU A to return the source to the idle source level at the end of a sweep:

smua.trigger.endsweep.action = smua.SOURCE_IDLE

Configuring measurements during a sweep

You can make measurements during a sweep using the smuX.trigger.measure.Y() function. When sweeps are run, measurements are stored in the specified reading buffer for later recall. You can specify which reading buffer stores the readings. For example, to store the voltage readings made during the sweep, send the commands:

smua.trigger.measure.v(vbuffername)

smua.trigger.measure.action = smua.ENABLE

To recall sweep data using the front panel:

1. Press the RECALL key.
2. Select DATA or STATISTICS.
3. If you selected DATA: Select the buffer and use the navigation wheel or cursor keys to choose reading numbers to display.
4. If you selected STATISTICS: Select the buffer and use the navigation wheel or cursor keys to choose MEAN, STD DEV, SAMPLE SIZE, MINIMUM, MAXIMUM, or PK-PK.

Recalling readings from the reading buffer using the front panel can be done only if one of the dedicated reading buffers is used to store the sweep data.

To recall sweep data using remote commands:

Use the printbuffer() function to request buffer readings.

See Recalling readings for details about recalling data from the buffer.

Source and measurement delays

Whenever the source‑measure unit (SMU) outputs a source value in a sweep, it also applies the programmed source delay. The default source delay is zero (0) seconds. Set an additional source delay using the smu X.source.delay attribute.

Whenever the SMU makes a measurement in a sweep, it also applies any configured measurement delays. Use the smuX.measure.delay attribute to program a specific measurement delay. The default measurement delay varies by measure range.

Initiating and running sweeps

To run a sweep, you must configure the number of sweep points to output and the number of sweeps to perform. See Triggering for more information.

Examples:

To start a sweep, use the smuX.trigger.initiate() function. Sweeps are overlapped operations, so you can use the waitcomplete() function to suspend further operation until the sweep is complete.

To sweep 15 source points:

smua.trigger.count = 15

To perform eight sweeps:

smua.trigger.arm.count = 8

Aborting a sweep

You can use the smuX.abort() function to terminate all overlapped operations on a source‑measure unit (SMU), including sweeps. It returns the SMU to the idle state of the remote trigger model. See Triggering for more information.

Sweeping using factory scripts

Factory script functions that perform linear staircase, logarithmic staircase, and list sweeps are described in Factory scripts. You can use the factory script functions to execute simple sweeps or use them as examples for programming your own custom sweeps.

To run a sweep from the front panel:

1. Press the LOAD key, and then select FACTORY.
2. Select the name of the test to run.
3. Press the RUN key. Follow the display prompts to complete the test.

See Factory scripts for more information about using factory scripts.

Press the RECALL key to access sweep data stored in dedicated reading buffer 1. See Reading buffers for more details about the buffer.

Sweep programming examples

The following topics provide procedures for programming and running a sweep. Each of these procedures includes commands for a typical sweep example. The following table summarizes parameters for each of these examples.

You can retrieve the source code for the factory scripts by using the scriptVar.list() or scriptVar.source commands.

Sweep example parameters
Sweep type	Parameters for sweep examples
Linear staircase sweep	Start current: 1 mA
	Stop current: 10 mA
	Settling time: 0.1 s
	Number of points: 10
Pulse current sweep	Bias current: 1 mA
	On current: 10 mA
	Pulse on time: 10 ms
	Pulse off time: 50 ms
	Number of points: 10
List sweep	Points: 3 V, 1 V, 4 V, 5 V, 2 V
	Settling time 0.1 s
	Number of points: 5

Linear staircase sweep example

The programming example below illustrates a staircase sweep.

-- Restore 2600B defaults. smua.reset() -- Set compliance to 1 V. smua.source.limitv = 1	1. Configure source functions. Restores defaults and sets the compliance limit to 1 V.
-- Linear staircase sweep -- 1 mA to 10 mA, 0.1 second delay, -- 10 points. SweepILinMeasureV(smua, 1e-3, 10e-3, 0.1, 10)	2. Configure and execute the sweep. Configures a linear staircase current sweep from 1 mA to 10 mA with 10 points and a 0.1 second settling time.
printbuffer(1, 10, smua.nvbuffer1.readings)	3. Request readings. Requests readings from buffer 1.

Pulse current sweep example

The programming example below illustrates a pulse sweep.

-- Restore 2600B defaults. smua.reset() -- Set compliance to 10 V. smua.source.limitv = 10	1. Configure source functions. Restores defaults and sets the compliance to 10 V.
-- Pulse current sweep, 1 mA bias, -- 10 mA level, 10 ms pulse on, -- 50 ms pulse off, 10 cycles. PulseIMeasureV(smua, 1e-3, 10e-3, 20e-3, 50e-3, 10)	2. Configure and execute the sweep. Configures a 10 mA pulse current sweep with a 10 ms pulse on time, a 50 ms pulse off time, and 10 pulse-measure cycles.
printbuffer(1, 10, smua.nvbuffer1.readings)	3. Request readings. Requests readings from buffer 1.

List sweep example

The programming example below illustrates a list sweep.

-- Restore 2600B defaults. smua.reset() -- Set compliance to 10 mA. smua.source.limiti = 10e-3	1. Configure source functions. Restores defaults and set the compliance to 10 mA.
-- Define voltage list. vlist = {3, 1, 4, 5, 2} -- List sweep, channel A, 3 V, 1 V, 4 V, -- 5 V, 2 V steps, 0.1 s delay, 5 points. SweepVListMeasureI(smua, vlist, 0.1, 5)	2. Configure and execute the sweep. Configures a list sweep with 3 V, 1 V, 4 V, 5 V, and 2 V points using a 0.1 second settling time.
printbuffer(1, 5, smua.nvbuffer1.readings)	3. Request readings. Requests readings from buffer 1.

Enabling and disabling relative offset from the front panel

To enable and use the relative offset feature, press the REL key on the front panel. The reading (which becomes the relative offset value) is subtracted from itself, causing the SMU to display a zero value. The reading is stored for use with subsequent measurements. Press the REL key a second time to disable the relative offset.

Defining a relative offset value from the front panel

You can establish a relative offset value for the selected measurement function.

To establish a relative offset value from the front panel:

1. Press the CONFIG key and then the REL key.
2. Select the measurement function (CURRENT, VOLTAGE, OHMS, or WATTS).
3. Press ENTER or the navigation wheel. The present relative offset value is displayed.
4. Set the relative offset value.
5. With the relative offset value displayed, press the ENTER key or the navigation wheel, and then press the EXIT (LOCAL) key to back out of the menu structure.

Relative offset commands

Relative offset commands are summarized in the following table.

Relative offset commands
Command*	Description
To set relative offset values:
smuX.measure.rel.leveli = relval	Set current relative offset value
smuX.measure.rel.levelp = relval	Set power relative offset value
smuX.measure.rel.levelr = relval	Set resistance relative offset value
smuX.measure.rel.levelv = relval	Set voltage relative offset value
To enable or disable relative offset:
smuX.measure.rel.enablei = smuX.REL_OFF	Disable current relative offset
smuX.measure.rel.enablep = smuX.REL_OFF	Disable power relative offset
smuX.measure.rel.enabler = smuX.REL_OFF	Disable resistance relative offset
smuX.measure.rel.enablev = smuX.REL_OFF	Disable voltage relative offset
smuX.measure.rel.enablei = smuX.REL_ON	Enable current relative offset
smuX.measure.rel.enablep = smuX.REL_ON	Enable power relative offset
smuX.measure.rel.enabler = smuX.REL_ON	Enable resistance relative offset
smuX.measure.rel.enablev = smuX.REL_ON	Enable voltage relative offset
* smuX can be smua for channel A or smub for channel B

Relative offset programming example

The programming example below performs a current measurement, uses it as the relative offset value, and enables current relative offset:

-- Measure and set present current value as the relative offset.

smua.measure.rel.leveli = smua.measure.i()

-- Enable current relative offset.

smua.measure.rel.enablei = smua.REL_ON

Filter types

The 2600B provides two averaging filters and a median filter. The power‑on default is the repeating filter.

The averaging filters are repeating and moving, as shown in the following figure. For the repeating filter, the stack (filter count) is filled, and the conversions are averaged to yield a reading. The stack is then cleared, and the process starts over.

The moving filter uses a first-in, first-out stack. When the stack (filter count) becomes full, the measurement conversions are averaged, yielding a reading. For each subsequent conversion placed into the stack, the oldest conversion is discarded. The stack is averaged again, yielding a new reading.

The median filter is used to pass the reading that is nearest to the middle from a group of readings that are arranged according to size. The median filter uses a first-in, first-out stack similar to the moving filter. For each subsequent conversion placed into the stack, the oldest conversion is discarded. The median is then redetermined.

When a moving filter or a median filter is first enabled, the stack is empty. The first reading conversion is placed in the stack and is then copied to the other stack locations to fill it. Thus, the first filtered reading is the same as the first reading conversion. The normal moving filter process continues. A true average or median reading is only yielded when the stack is filled with new reading conversions (no copies in the stack). For example, in the figure for the moving filter, it makes ten filtered readings to fill the stack with new reading conversions. The first nine filtered readings are calculated using copied reading conversions.

Response time

The filter parameters have speed and accuracy trade-offs for the time needed to display, store, or output a filtered reading. These affect the number of reading conversions for speed versus accuracy and response to input signal changes.

The filter type and count affect the overall reading speed. The moving average filter is much faster than the repeat average filter because the instrument does not have to refill the filter stack for each reading. Also, the number of readings averaged affects reading speed; as the number of readings averaged increases, the reading speed decreases.

Enabling the filter from the front panel

The filter is enabled by pressing the FILTER key on the front panel. The FILT indicator is on while the filter is enabled. Pressing FILTER a second time disables the filter.

Configuring the filter from the front panel

Filter type and count are configured from the filter configuration menu on the front panel. The same filter configuration is used for all measurement functions.

To configure the filter:

1. Press the CONFIG key and then the FILTER key.
2. Select TYPE, and then select the filter type: AVERAGE or MEDIAN.
   • AVERAGE: Use this menu item to select an averaging filter, then select the averaging filter type: MOVING or REPEAT.
   • MEDIAN: Use this menu item to select a median filter. The MOVING filter type is the only option.
3. Select COUNT, and then specify the filter count (1 to 100 readings).

Setting the filter using a remote interface

The following table summarizes the filter commands. See the TSP command reference for details about commands.

Filter commands
Command*	Description
smuX.measure.filter.count = count	Set filter count (1 to 100)
smuX.measure.filter.enable = smuX.FILTER_ON	Enable filter
smuX.measure.filter.enable = smuX.FILTER_OFF	Disable filter
smuX.measure.filter.type = smuX.FILTER_MEDIAN	Select median filter type
smuX.measure.filter.type = smuX.FILTER_MOVING_AVG	Select moving average filter type
smuX.measure.filter.type = smuX.FILTER_REPEAT_AVG	Select repeating average filter type
* smuX can be smua for channel A or smub for channel B

Filter programming example

The programming example below illustrates how to set the following filter options:

• Filter type: Moving average
• Filter count: 10
• Filter state: Enabled

-- Set the program count to 10.

smua.measure.filter.count = 10

-- Set the moving average filter type.

smua.measure.filter.type = smua.FILTER_MOVING_AVG

-- Enable the filter.

smua.measure.filter.enable = smua.FILTER_ON

Understanding high-capacitance mode

The source‑measure unit (SMU) in the 2600B drives 10 nF of capacitance in normal operation. Typically, an internal capacitor across the current measuring element provides phase lead to compensate for the phase lag caused by the load capacitance on the output. This internal capacitance across the range resistance limits the speed for a specific measurement range.

The SMU in the 2600B implements frequency compensation to achieve the highest throughput possible for a 10 nF or less load. In addition, you must consider the settling time, voltage range, measure delay, the quality of the capacitor, the current measure range resistor, and the load resistor.

In normal operation, the SMU in the 2600B can drive capacitive loads as large as 10 nF. In high-capacitance mode, the SMU can drive a maximum of 50 µF of capacitance.

When high-capacitance mode is enabled, a minimum load capacitance of 100 nF is recommended. In absence of this minimum load capacitance, overshoot and ringing may occur.

Highest throughput is achieved by using normal operation. In high‑capacitance mode, the speed of the 2600B SMU is reduced to compensate for the larger load capacitance. Stability is achieved by inserting an internal capacitance across the current measuring element of the SMU. This internal capacitor limits the speed for the source and measurement ranges. Therefore, when optimizing the speed of your test configuration in high-capacitance mode, you must consider the settling time, voltage, and current ranges, measure delay, quality of the load capacitor, and load resistance.

Understanding source settling times

Each 2600B source‑measure unit (SMU) can drive up to 50 µF of a capacitance in high‑capacitance mode. To accomplish this, the speed of the 2600B SMU is reduced. Source settling times increase when high‑capacitance mode is enabled. The following tables compare the source settling times in normal and high‑capacitance modes.

Model 2601B, 2602B, and 2604B source settling times
Range	Normal mode	High-capacitance mode
100 mV	50 µs	200 µs
1 V	50 µs	200 µs
6 V	100 µs	200 µs
40 V	150 µs	7 ms
Model 2611B, 2612B, 2614B, 2634B, 2635B, and 2636B source setting times
Range	Normal mode	High-capacitance mode
200 mV	50 µs	600 µs
2 V	50 µs	600 µs
20 V	110 µs	1.5 ms
200 V	700 µs	20 ms

In high-capacitance mode, the frequency compensation capacitance across the measure range resistors increases. This increase causes longer settling times on some current measure ranges. The same range elements that are used to measure current are used to source current. As a result, the current limit response times respond in a similar manner.

Current measure and source settling times
Current measure range	Normal mode (typical)	High capacitance mode (typical)
1 A to 1.5 A (2611B, 2612B, 2614B, 2634B, 2635B, 2636B)	120 µs	120 µs (RLOAD > 6 O)
1 A to 3 A (2601B, 2602B, 2604B)	80 µs	120 µs (RLOAD > 2 O)
100 mA	100 µs	100 µs
10 mA	80 µs	100 µs
1 mA	100 µs	3 ms
100 µA	150 µs	3 ms
10 µA	500 µs	230 ms
1 µA	2 ms	230 ms

When high-capacitance mode is enabled, the amount of time to change the current measure range increases for each SMU. The current measure range and the current limit range are locked together. Setting the current limit automatically updates the measure range.

Adjusting the voltage source

When driving large capacitive loads with high-capacitance mode enabled, the response time may be lengthened by the current limit. For example, see the table titled "Current measure and source settling times" in Understanding source settling times. If a 1 µF capacitor charges to 10 V in 10 µs with a 1 A limit and the limit is set to 100 nA, the charging time is 100 seconds, as shown in the following equation.

The total response times while in high-capacitance mode are a combination of the time spent charging the capacitor (current limit) or the response time, whichever is greater. There is a direct relationship between the current limit and the charging time. As the current limit decreases, the amount of time required to charge the capacitor increases.

Understanding the capacitor

Based on the capacitor dielectric absorption, the settling time may change and the values in the "Current measure and source settling times" table in Understanding source settling times may differ.

Tantalum or electrolytic capacitors are well known for long dielectric absorption settling times. Film capacitors and ceramics perform better, with NPO/COG dielectric ceramics yielding the best settling response.

Charging the capacitor and making readings

To charge and read a capacitor in high-capacitance mode:

1. Set the current limit to a value that is higher than the value that is used for the measurement (for example, if measuring at 10 µA, the initial current limit can be set to 1 A).
2. After the capacitor charges, lower the current limit and measure range to obtain the current measurement.

Enabling high-capacitance mode

Before enabling high-capacitance mode, note the following:

• It is important to read High-capacitance mode to understand the impact of high-capacitance mode.
• Test the device under test (DUT) and the capacitor to determine the best current limit and range of output voltages.
• The settling times can vary based on the DUT. It is important to test the limits of the DUT before you use high‑capacitance mode.
• Test the DUT for the appropriate current limit and output voltages.
• For optimal performance, do not continuously switch between normal mode and high‑capacitance mode.
• Before you charge the capacitor, start with 0 (zero) voltage across the capacitor.

Failure to test the DUT for the appropriate current limit and output voltages can result in damage to or destruction of the DUT.

To enable high-capacitance mode from the front panel:

1. Press the CONFIG key.
2. Press the SRC key and then select HIGHC-MODE.
3. Select SRC-ENABLE and then press the navigation wheel (or the ENTER key).
4. Select ENABLE and then press the navigation wheel (or the ENTER key).
5. Press the EXIT (LOCAL) key to back out of the menu structure.

To enable high-capacitance mode using a remote interface:

smuX.source.highc = smua.ENABLE

Turning on high‑capacitance mode has the following effects on the source‑measure unit (SMU)* settings:

• smuX.measure.autorangei is set to smuX.AUTORANGE_FOLLOW_LIMIT and cannot be changed.
• Current ranges below 1 µA are not accessible.
• If smuX.source.limiti is less than 1 µA, it is raised to 1 µA.
• If smuX.source.rangei is less than 1 µA, it is raised to 1 µA.
• If smuX.source.lowrangei is less than 1 µA, it is raised to 1 µA.
• If smuX.measure.lowrangei is less than 1 µA, it is raised to 1 µA.

* smuX can be smua for channel A or smub for channel B

Measuring current using high-capacitance mode

The following inputs are required to test leakage using the factory leakage script, as shown in the following script example.

• SMU: Sets the 2600B source‑measure unit to use
• levelv: Sets the output voltage level
• limiti: Sets the current limit for discharging or charging the capacitor
• sourcedelay: Solves the following equation to determine the amount of time before making a current reading:
  
  Where: i is the limiti setting (current limit)
• measurei: Sets the current measure range
• measuredelay: Defines the delay to wait after lowering the current limit before making the measurement

Script example

Use the smuX.source.highc attribute to set and control the options for high‑capacitance mode.

The programming examples and figure below illustrate how to enable high-capacitance mode on SMU A.

1. To enable high-capacitance mode, send:

-- Enables high-capacitance mode.

smua.source.highc = smua.ENABLE

2. To run the i_leakage_measure() function in the KIHighC factory script, send:

-- Charges the capacitor.

smua.source.levelv = 5

smua.source.output = smua.OUTPUT_ON

delay(1)

imeas = i_leakage_measure(smua, 0, 1, 300e-3, 10e-6, 100e-3)

-- The parameters in the i_leakage_measure() function represent

-- the following:

-- smu = smua

-- levelv = 0 V

-- limiti = 1 A

-- sourcedelay = 300 ms

-- measurei = 10 uA range

-- measuredelay = 100 ms

Adjust the voltage level and source delays based on:

• The value and type of capacitor
• The magnitude of the voltage step
• The current measure range

Saving user setups

You can save the present 2600B setup to internal nonvolatile memory or a USB flash drive.

To save a user setup to nonvolatile memory from the front panel:

1. Configure the 2600B to the settings that you want to save.
2. Press the MENU key.
3. Select SETUP and then press the ENTER key.
4. Select the SAVE menu item and then press the ENTER key.
5. Select INTERNAL and then press the ENTER key.
6. Select the user number (1 through 5) and press the ENTER key.

To save a user setup to an external USB flash drive from the front panel:

1. Configure the 2600B to the settings that you want to save.
2. Insert the USB flash drive into the USB port on the front panel of the 2600B.
3. Press the MENU key.
4. Select SETUP and then press the ENTER key.
5. Select SAVE and then press the ENTER key.
6. Select USB1. The file name setup000.set is displayed.
7. Turn the navigation wheel to change the last three digits of the file name and then press the ENTER key.

To save and recall user setups using remote commands:

Use the setup.save() and setup.recall() functions to save and recall user setups. The following example saves the present setup as setup 1, and then recalls setup 1.

-- Save the present setup to nonvolatile memory.

setup.save(1)

-- Recall the saved user setup from nonvolatile memory.

setup.recall(1)

Recalling a saved setup using the front panel

You can recall setups from internal nonvolatile memory or a USB flash drive.

To recall a saved setup from the front panel:

1. Press the MENU key to access the main menu.
2. Select SETUP, and then press the ENTER key.
3. Select the RECALL menu item, and then press the ENTER key.
4. Select one of the following:
   • INTERNAL
   • USB1
5. For INTERNAL only, do one of the following:
   • Select FACTORY to restore factory defaults, then press the ENTER key.
   • Select the user number (1 through 5), then press the ENTER key.
6. USB1 only: Select the appropriate file and then press the ENTER key.

Start-up configuration

The start-up configuration allows you to apply specific settings every time the instrument powers up. The settings are defined in a user setup. You can also select the factory default setup.

To select the power-on setup from the front panel:

1. Press the MENU key to access the main menu.
2. Select SETUP, and then press the ENTER key.
3. Select POWERON, and then press the ENTER key.
4. Select the configuration to use.
5. Press the ENTER key.
6. Use the EXIT (LOCAL) key to return to the main display.

To select the power-on setup using remote commands:

Use the setup.poweron attribute to select which setup to use when the instrument powers up. To set the setup.poweron configuration attribute:

setup.poweron = n

Where n is:

• 0 (*RST or reset() factory defaults)
• 1 to 5 (user setup 1 to 5)

Restoring factory default setups using remote commands

Use one of the reset functions to return the 2600B to the original factory defaults. An example of each type of reset is shown in the following program examples.

Restore all factory defaults of all nodes on the TSP-Link^TM network:

reset()

Restore all factory defaults (note that you cannot use *rst in a script):

*rst

Restore all factory defaults:

setup.recall(0)

Restore channel A defaults:

smua.reset()

Reset only the local TSP-Link node:

localnode.reset()

Reading buffer options

The following list outlines the menu structure and menu items associated with front‑panel reading buffer control. This section provides a description for each reading buffer option. Use the procedure in Configuring reading buffers as a guideline to configure these reading buffer options.

CHANA-BUFF: Configures channel A buffer.

• DEST: Set the data storage destination (buffer 1, buffer 2, or none).
• BUFFER1: Configure buffer 1.
  • CLEAR: Clear buffer (YES or NO).
  • ELEMENTS: Enable (ON) or disable (OFF) data‑storage elements.
  • SRC-VAL: Enable or disable source values.
  • TSTAMP: Enable or disable timestamps.
• BUFFER2: Configure buffer 2.
  • CLEAR: Clear buffer (YES or NO).
  • ELEMENTS: Enable (ON) or disable (OFF) data‑storage elements.
  • SRC-VAL: Enable or disable source values.
  • TSTAMP: Enable or disable timestamps.

CHANB-BUFF: Configures channel B buffer (2602B, 2604B, 2612B, 2614B, 2634B, and 2636B only).

• DEST: Set the data storage destination (buffer 1, buffer 2, or none).
• BUFFER1: Configure buffer 1.
  • CLEAR: Clear buffer (YES or NO).
  • ELEMENTS: Enable (ON) or disable (OFF) data storage elements.
  • SRC-VAL: Enable or disable source values.
  • TSTAMP: Enable or disable timestamps.
• BUFFER2: Configure buffer 2.
  • CLEAR: Clear buffer (YES or NO).
  • ELEMENTS: Enable (ON) or disable (OFF) data storage elements.
  • SRC-VAL: Enable or disable source values.
  • TSTAMP: Enable or disable timestamps.

Configuring reading buffers

To configure reading buffers from the front panel:

Enabling or disabling the source value or the timestamp is optional.

1. Press the CONFIG key.
2. Press the STORE key and then choose one of the following:
   • CHANA-BUFF
   • CHANB-BUFF (2602B, 2604B, 2612B, 2614B, 2634B, and 2636B only)
3. To select a storage destination, select the DEST option, and then choose one of the following:
   • CHANx-BUFF1
   • CHANx-BUFF2
   • NONE
     
     CHANx: CHANA refers to SMU channel A and CHANB refers to SMU channel B (2602B, 2604B, 2612B, 2614B, 2634B, and 2636B only).
4. Select BUFFER1 or BUFFER2.
5. Clear the buffer by turning the navigation wheel to select CLEAR > YES.
6. Turn the navigation wheel to highlight ELEMENTS, and then press the navigation wheel (or the ENTER key).

You must clear the reading buffer before you can enable or disable the source value or the timestamp options.

1. Configure the timestamp elements of the reading buffer:

   a. Turn the navigation wheel to highlight TSTAMP.

   b. Press the navigation wheel (or the ENTER key).

   c. Select OFF or ON and then press the navigation wheel (or the ENTER key).

2. Configure the source value elements of the reading buffer:

   a. Turn the navigation wheel to highlight SRC-VAL.

   b. Press the navigation wheel (or the ENTER key).

   c. Select OFF or ON.

3. Press the EXIT (LOCAL) key to return to the main menu.

The 2601B, 2611B, and 2635B buffer configuration menu items are accessed in the same manner, except for channel selection.

Appending or overwriting existing reading buffers

When storing data to a reading buffer that already holds data, the new data can be appended to the reading buffer data, or it can overwrite the old data.

To configure the instrument to append or overwrite measurements the next time data is acquired:

1. Press the CONFIG key.
2. Select STORE, and then select STORAGE-MODE. The Storage Mode menu is shown.
3. Select one of the following:
   • APPEND
   • OVERWRITE
4. Press the EXIT (LOCAL) key to return to the main menu.

Storage operation

Use this option to initiate a storage operation and to configure the number of readings to acquire during the storage operation. The reading count can be more than 60,000 if timestamps and source values are enabled. The count can be more than 140,000 if timestamps and source values are disabled.

To store the maximum number of readings in a reading buffer, disable the source values and timestamps for that reading buffer.

To specify the number of readings and initiate the storage operation:

1. From the front panel, press the STORE key, and then select TAKE_READINGS.
2. Use the navigation wheel to select the number of readings.
3. Press the navigation wheel to switch to edit mode.
4. Turn the navigation wheel to change the numeric value.
5. Press the navigation wheel to save the numeric value.
6. Press the ENTER key to save the count.
7. Press the OUTPUT ON/OFF control to start making readings.

If the output-off mode is ZERO or the output is already on, the instrument starts acquiring readings when the ENTER key is pressed. Otherwise, the instrument starts acquiring readings when the output is turned on.

Saving reading buffers

You can save the dedicated reading buffers to nonvolatile memory or you can save them to a USB flash drive.

The instrument restores the dedicated reading buffers from internal nonvolatile memory when the instrument is turned off and back on.

You can also save reading buffer data to a .csv file using the web interface.

Saving the reading buffers to nonvolatile memory

After the measurements are complete, you can save the reading buffer data to the nonvolatile memory in the instrument.

To save the reading buffer data:

1. From the front panel, press the STORE key, and then select SAVE.
2. Select INTERNAL to save to internal nonvolatile memory.
3. Select one of the following:
   • SMUA_BUFFER1
   • SMUA_BUFFER2
   • SMUB_BUFFER1 (2602B, 2604B, 2612B, 2614B, 2634B, and 2636B only)
   • SMUB_BUFFER2 (2602B, 2604B, 2612B, 2614B, 2634B, and 2636B only)
4. The front panel displays Saving... This may take awhile.
5. Press the EXIT (LOCAL) key to return to the main menu.

Saving the reading buffer to a USB flash drive

After the measurements are complete, you can save the reading buffer data to a USB flash drive.

To save the reading buffer data to a USB flash drive:

1. Insert the USB flash drive into the USB port.
2. Press the STORE key and use the navigation wheel to select SAVE.
3. Select USB1.
4. Select one of the following file formats:
   • CSV
   • XML
5. Use the navigation wheel to select the reading buffer.
6. Use the navigation wheel to change the file name.
7. Press the navigation wheel or the ENTER key to save the file.
8. Press the EXIT (LOCAL) key to return to the main menu.

Recalling readings

To recall the data stored in a reading buffer:

1. Press the RECALL key.
2. Select DATA or STATISTICS.
3. Select the buffer to display: CHANx-BUFF1 or CHANx-BUFF2 (where X is A on the 2601B, 2611B, or 2635B, or X is A or B on the 2602B, 2604B, 2612B, 2614B, 2634B, or 2636B). The data or statistics are displayed.
   • If you are recalling data, the reading display is on the top left, and the buffer location number is on the right. The source values are on the lower left side of the display (if enabled); the timestamp (if used) is on the lower right side.
   • If you are recalling statistics, the information includes values for MEAN, STD DEV, SAMPLE SIZE, MINIMUM, MAXIMUM, and PK-PK.
   • The source display field identifies the buffer: SrcA1 (buffer 1), SrcA2 (buffer 2). For two‑channel instruments (2602B, 2604B, 2612B, 2614B, 2634B, 2636B): SrcB1 (buffer 1), SrcB2 (buffer 2).

Buffer location number

The buffer location number indicates the memory location of the source-measure reading. For example, location #000001 indicates that the displayed source-measure reading is stored at the first memory location.

Timestamp

If the timestamp is enabled, the first source-measure reading stored in the buffer (#0000001) is timestamped at 0.000 seconds. Subsequent readings are timestamped relative to when the first measurement was made. The interval between readings depends on the reading rate.

Displaying other buffer readings and statistics

To display other readings and statistics in the reading buffer:

1. While still in the buffer recall mode:
   • If viewing the data stored in the buffer, turn the navigation wheel to increment and decrement the selected digit of the location number by one. Press the navigation wheel and then turn it or use the CURSOR keys to move to the next digit.
   • If viewing the statistics stored in the buffer, turn the navigation wheel or use the CURSOR keys to scroll between MEAN, STD DEV, SAMPLE SIZE, MINIMUM, MAXIMUM, and PK-PK.
2. To exit from the reading buffer recall mode, press the EXIT (LOCAL) key.

Dual buffer example

The programming example below shows a script that stores current and voltage readings using buffer 1 for current and buffer 2 for voltage readings. The 2600B stores 100 current and voltage readings and then recalls all 100 sets of readings.

-- Restore 2600B defaults.

smua.reset()

-- Select measure I autorange.

smua.measure.autorangei = smua.AUTORANGE_ON

-- Select measure V autorange.

smua.measure.autorangev = smua.AUTORANGE_ON

-- Select ASCII data format.

format.data = format.ASCII

-- Clear buffer 1.

smua.nvbuffer1.clear()

-- Clear buffer 2.

smua.nvbuffer2.clear()

-- Set buffer count to 100.

smua.measure.count = 100

-- Set measure interval to 0.1 s.

smua.measure.interval = 0.1

-- Select source voltage function.

smua.source.func = smua.OUTPUT_DCVOLTS

-- Output 1 V.

smua.source.levelv = 1

-- Turn on output.

smua.source.output = smua.OUTPUT_ON

-- Store current readings in buffer 1, voltage readings in buffer 2.

smua.measure.overlappediv(smua.nvbuffer1, smua.nvbuffer2)

-- Wait for buffer to fill.

waitcomplete()

-- Turn off output.

smua.source.output = smua.OUTPUT_OFF

-- Output buffer 1 readings 1 to 100.

printbuffer(1, 100, smua.nvbuffer1)

-- Output buffer 2 readings 1 to 100.

printbuffer(1, 100, smua.nvbuffer2)

Dedicated reading buffer designations

Each source‑measure unit (SMU) contains dedicated reading buffers:

• smua.nvbuffer1 (buffer 1 for channel A)
• smua.nvbuffer2 (buffer 2 for channel A)
• smub.nvbuffer1 (buffer 1 for channel B)
• smub.nvbuffer2 (buffer 2 for channel B)

To access a reading buffer, include the name of the SMU in the attribute. For example, the following command stores readings from channel A into buffer 1:

smua.measure.overlappedi(smua.nvbuffer1)

Dedicated reading buffer example

The following programming example illustrates how to store data using dedicated reading buffer 1. In the example, the 2600B loops for voltages from 0.01 V to 1 V with 0.01 V steps (performing a staircase sweep), stores 100 current readings and source values in buffer 1, and then recalls all 100 readings and source values.

-- Restore 2600B defaults.

smua.reset()

-- Select channel A display.

display.screen = display.SMUA

-- Display current.

display.smua.measure.func = display.MEASURE_DCAMPS

-- Select measure I autorange.

smua.measure.autorangei = smua.AUTORANGE_ON

-- Select ASCII data format.

format.data = format.ASCII

-- Clear buffer 1.

smua.nvbuffer1.clear()

-- Enable append buffer mode.

smua.nvbuffer1.appendmode = 1

-- Enable source value storage.

smua.nvbuffer1.collectsourcevalues = 1

-- Set the count to 1.

smua.measure.count = 1

-- Select the source voltage function.

smua.source.func = smua.OUTPUT_DCVOLTS

-- Set the bias voltage to 0 V.

smua.source.levelv = 0.0

-- Turn on the output.

smua.source.output = smua.OUTPUT_ON

-- Loop for voltages from 0.01 V to 1 V.

for v = 1, 100 do

-- Set the source voltage.

smua.source.levelv = v * 0.01

-- Measure the current and store in nvbuffer1.

smua.measure.i(smua.nvbuffer1)

end

-- Turn off the output.

smua.source.output = smua.OUTPUT_OFF

-- Output readings 1 to 100.

printbuffer(1, smua.nvbuffer1.n, smua.nvbuffer1.readings)

-- Output source values 1 to 100.

printbuffer(1, smua.nvbuffer1.n, smua.nvbuffer1.sourcevalues)

Reading buffer commands

The following tables summarize commands associated with the reading buffers. See TSP command reference for detailed reading buffer command information.

Reading buffer commands*
Command	Description
Commands to save and clear readings
smuX.savebuffer(smuX.nvbufferY)	Saves the reading buffer to the nonvolatile memory on the 2600B.
smuX.nvbuffer1.clear()	Clears buffer 1.
smuX.nvbuffer2.clear()	Clears buffer 2.
mybuffer = smuX.makebuffer(n)	Creates a dynamically allocated buffer for n readings.
mybuffer = nil	Deletes the dynamically allocated buffer.
savebuffer(smuX.nvbuffer1,"csv", "/usb1/mybuffer.csv")	Saves the reading buffer to a USB flash drive.

Command	Description
Commands to store readings
smuX.measure.count = count	The number of measurements to acquire.
smuX.measure.overlappedi(rbuffer)	Makes current measurements; stores readings in rbuffer.
smuX.measure.overlappediv(ibuffer, vbuffer)	Makes both current and voltage measurements; stores current readings in ibuffer and stores voltage readings in vbuffer.
smuX.measure.overlappedp(rbuffer)	Makes power measurements; stores readings in rbuffer.
smuX.measure.overlappedr(rbuffer)	Makes resistance measurements; stores readings in rbuffer.
smuX.measure.overlappedv(rbuffer)	Makes overlapped voltage measurements; stores readings in rbuffer.
smuX.measure.v(rbuffer)	Makes voltage measurements; stores readings in rbuffer.
smuX.measure.i(rbuffer)	Makes current measurements; stores readings in rbuffer.
smuX.measure.iv(ibuffer, vbuffer)	Makes both current and voltage measurements; stores current readings in ibuffer and stores voltage readings in vbuffer.
smuX.measure.r(rbuffer)	Makes resistance measurements; stores readings in rbuffer.
smuX.measure.p(rbuffer)	Makes power measurements; stores readings in rbuffer.
smuX.trigger.measure.v(rbuffer)	Configures voltage measurements to be made during a sweep, including where readings are stored (rbuffer).
smuX.trigger.measure.i(rbuffer)	Configures current measurements to be made during a sweep, including where readings are stored (rbuffer).
smuX.trigger.measure.r(rbuffer)	Configures resistance measurements to be made during a sweep, including where readings are stored (rbuffer).
smuX.trigger.measure.p(rbuffer)	Configures power measurements to be made during a sweep, including where readings are stored (rbuffer).
smuX.trigger.measure.iv(ibuffer, vbuffer)	Configures both current and voltage measurements to be made during a sweep, including where readings are stored; current readings are stored in ibuffer and voltage readings are stored in vbuffer.

Command	Description
Commands to access readings
printbuffer(start_index, end_index, st_1, st_2, ... st_n)	Prints data from buffer subtables: start_index (starting index of values to print) end_index (ending index of values to print) st_1, st_2, ... st_n (subtables from which to print, each separated by a comma)

* smuX can be smua for channel A or smub for channel B

Buffer storage control attributes

The following table contains buffer storage control attributes.

Before changing the collectsourcevalues, collecttimestamps, or timestampresolution attributes, you must clear the buffer using the smuX.nvbuffer1.clear() or smuX .nvbuffer2.clear() command.

Buffer storage attribute	Description
appendmode	The append mode is either off or on. When the append mode is off, a new measurement to this buffer overwrites the previous contents. When the append mode is on, the first new measurement is stored at the end of the existing data. This attribute is off when the buffer is created.
cachemode	When this attribute is on, the reading buffer cache improves access speed to reading buffer data. When running successive operations that overwrite reading buffer data without running any commands that automatically invalidate the cache, the reading buffer may return stale cache data. This attribute is initialized to on when the buffer is created.
collectsourcevalues	When this attribute is on, source values are stored with readings in the buffer. This value, off or on, can be changed only when the buffer is empty. When the buffer is created, this attribute is initialized to off.
collecttimestamps	When this attribute is on, timestamps are stored with readings in the buffer. This value, off or on, can be changed only when the buffer is empty. When the buffer is created, this attribute is initialized to off.
fillcount	The reading buffer fill count sets the number of readings to store before restarting at index 1. If the value is 0, then the capacity of the buffer is used. This attribute is only used when the fillmode attribute is set to FILL_WINDOW.
fillmode	The reading buffer fill mode controls how new data is added to the reading buffer. When this attribute is set to FILL_ONCE, the reading buffer does not overwrite readings. If the buffer fills up, new readings are discarded. When this attribute is set to FILL_WINDOW, new readings are added after existing data until the buffer holds fillcount elements. Once there are fillcount elements, new data starts overwriting data starting at index 1.
timestampresolution	The timestamp resolution, in seconds. When the buffer is created, its initial resolution is 0.000001 seconds. At this resolution, the reading buffer can store unique timestamps for up to 71 minutes. This value can be increased for long tests.

Buffer read-only attributes

The following table contains buffer read‑only attributes that access the buffer parameters.

Attribute	Description
basetimestamp	The timestamp of when the reading at rb[1] was stored, in seconds from midnight January 1, 1970 GMT. See Time and date values for additional details.
capacity	The total number of readings that can be stored in the reading buffer.
n	The number of readings in the reading buffer.
next	This attribute indicates where the next element that is added to the reading buffer is stored.

Buffer storage control programming examples

The programming examples below illustrate the use of buffer storage control attributes.

Command	Description
smua.nvbuffer1.collectsourcevalues = 1	Enable source value storage.
smua.nvbuffer1.appendmode = 1	Enable buffer append mode.
smua.nvbuffer1.collecttimestamps = 0	Disable timestamp storage.
smua.nvbuffer1.timestampresolution = 0.001	Set timestamp resolution to 0.001024 s.
smua.nvbuffer1.fillcount = 50	Set 50 as the number of readings the buffer stores before restarting at index 1.
smua.nvbuffer1.fillmode = 0	Set the reading buffer to fill once (do not overwrite old data).

Buffer read-only attribute programming examples

The following programming examples illustrate use of buffer read‑only attributes.

Command	Description
number = smua.nvbuffer1.n	Request the number of readings in the buffer.
buffer_size = smua.nvbuffer1.capacity	Request buffer size.

Statistic attributes

Use the smuX.buffer.getstats() function to access the reading buffer data statistics. The table below lists the attributes that you can use to access the reading buffer statistics.

Attributes for accessing reading buffer data
Attribute	When returned	Description
n	Always	The number of data points on which the statistics are based
mean	When n > 0	The average of all readings added to the buffer
stddev	When n > 1	The standard deviation of all readings (samples) added to the buffer
min	When n > 0	A table containing data about the minimum reading value added to the buffer
max	When n > 0	A table containing data about the maximum reading value added to the buffer

If n equals zero (0), all other attributes are nil because there is no data to base any statistics on. If n equals 1, the stddev attribute is nil because the standard deviation of a sample size of 1 is undefined.

The min and max entries have the attributes described in the following table (bufferVar is the name of the buffer). See smuX.buffer.getstats() for additional information.

Min and max entry attributes
Attribute	Description
measurefunction	String indicating the function that was measured for the reading (current, voltage, ohms, or watts)
measurerange	The full-scale range value for the measurement range used when the measurement was made
reading	The reading value
sourcefunction	String indicating the source function at the time of the measurement (current or voltage)
sourceoutputstate	String indicating the state of the source (off or on)
sourcerange	Full-scale range value for the source range used when the measurement was made
sourcevalue	If bufferVar.collectsourcevalues is enabled, the sourced value in effect at the time of the reading
status	Status value for the reading; the status value is a floating-point number that encodes the status value into a floating-point value
timestamp	If bufferVar.collecttimestamps is enabled, the timestamp, in seconds, between when the reading was acquired and when the first reading in the buffer was acquired; adding this value to the base timestamp produces the actual time the measurement was acquired

Example:

The following programming example illustrates how to output mean and standard deviation statistics from buffer 1:

statistics = smua.buffer.getstats(smua.nvbuffer1)

print(statistics.mean, statistics.stddev)

Reading buffer attributes

Use the reading buffer attributes to access the reading buffer data. The table below displays the attributes that you can use to access the reading buffer data.

Recall attribute*	Description
measurefunctions	An array (a Lua table) of strings indicating the function measured for the reading (current, voltage, ohms, or watts).
measureranges	An array (a Lua table) of full-scale range values for the measure range used when the measurement was made.
readings	An array (a Lua table) of the readings stored in the reading buffer. This array holds the same data that is returned when the reading buffer is accessed directly; that is, rb[2] and rb.readings[2] access the same value.
sourcefunctions	An array (a Lua table) of strings indicating the source function at the time of the measurement (current or voltage).
sourceoutputstates	An array (a Lua table) of strings indicating the state of the source (off or on).
sourceranges	An array (a Lua table) of full-scale range values for the source range used when the measurement was made.
sourcevalues	If enabled, an array (a Lua table) of the sourced values in effect at the time of the reading.
statuses	An array (a Lua table) of status values for all the readings in the buffer. The status values are floating-point numbers that encode the status value into a floating-point value. See Buffer status.
timestamps	If enabled, an array (a Lua table) of timestamps, in seconds, of when each reading occurred. These are relative to the basetimestamp for the buffer. See Reading buffer commands.

* The default attribute is readings, which can be omitted.

Examples:

The following programming example illustrates how to output 100 channel A readings from buffer 1:

printbuffer(1, 100, smua.nvbuffer1.readings)

Similarly, the following outputs 100 channel A corresponding source values from buffer 1:

printbuffer(1, 100, smua.nvbuffer1.sourcevalues)

The default reading attribute is readings, which can be omitted. If readings is omitted, the following also outputs 100 channel A readings from buffer 1:

printbuffer(1, 100, smua.nvbuffer1)

Buffer status

The buffer reading status attribute includes the status information as a numeric value; see the following table for values. For example, to access status information for the second element of SMU channel A buffer 1, use the following command:

stat_info = smua.nvbuffer1.statuses[2]

Buffer status bits
Bit	Name	Hex value	Description
B0	Reserved	0x01	Reserved for future use
B1	Overtemp	0x02	Overtemperature condition
B2	AutoRangeMeas	0x04	Measure range was autoranged
B3	AutoRangeSrc	0x08	Source range was autoranged
B4	4Wire	0x10	4-wire (remote) sense mode was enabled
B5	Rel	0x20	Relative offset was applied to a reading
B6	Compliance	0x40	Source function was in compliance
B7	Filtered	0x80	Reading was filtered

Dynamic reading buffers

Reading buffers can also be allocated dynamically. You create and allocate the dynamic reading buffers with the smuX.makebuffer( n) command, where n is the number of readings the buffer can store. For example, the following command allocates a reading buffer named mybuffer that can store 100 readings:

mybuffer = smua.makebuffer(100)

You can delete allocated reading buffers by sending the following command:

mybuffer = nil

You can use dynamically allocated reading buffers interchangeably with the smuX.nvbufferY buffers that are described in Dedicated reading buffer designations.

Dynamically allocated buffer example

The programming example below illustrates how to store data to an allocated buffer called mybuffer. The 2600B stores 100 current readings in mybuffer and then recalls all the readings.

-- Restore 2600B defaults.

smua.reset()

-- Select measure I autorange.

smua.measure.autorangei = smua.AUTORANGE_ON

-- Select measure V autorange.

smua.measure.autorangev = smua.AUTORANGE_ON

-- Select ASCII data format.

format.data = format.ASCII

-- Set the buffer count to 100.

smua.measure.count = 100

-- Set the measure interval to 0.1 s.

smua.measure.interval = 0.1

-- Select the source voltage function.

smua.source.func = smua.OUTPUT_DCVOLTS

-- Set the source voltage to output 1 V.

smua.source.levelv = 1

-- Turn on the output.

smua.source.output = smua.OUTPUT_ON

-- Create a temporary reading buffer.

mybuffer = smua.makebuffer(smua.measure.count)

-- Store current readings in mybuffer.

smua.measure.overlappedi(mybuffer)

-- Wait for the buffer to fill.

waitcomplete()

-- Turn off the output.

smua.source.output = smua.OUTPUT_OFF

-- Output readings 1 to 100 from mybuffer.

printbuffer(1, 100, mybuffer)

-- Delete mybuffer.

mybuffer = nil

Using the remote trigger model

The source‑measure unit (SMU) in the 2600B has a remote trigger model that supports a wide range of triggering features for source sweeps, triggered measurements, and pulse actions.

Measurements using the trigger model can be made synchronously with sourcing actions or they can be made asynchronously. The following figures graphically illustrate both modes of the remote trigger model.

Remote trigger model: Normal (synchronous) mode

Remote trigger model: Asynchronous mode

When the smuX.trigger.measure.action attribute is set to smuX .DISABLE or smuX.ENABLE, the trigger model operates in synchronous measurement mode. When it is set to smu X.ASYNC, it operates in asynchronous mode.

Each section of the trigger model performs a function:

Idle state	If a sweep is not in process, the SMU is in the idle state. Use the smuX.trigger.initiate() function to move the SMU from the idle state to the arm layer.
Arm layer	Begins a sweep. Each sweep starts and ends in the arm layer.
Trigger layer	All source, measurement, and pulse actions occur in the trigger layer. Source: Outputs the programmed voltage or current source value. Measurement: Where the current, voltage, resistance, and power measurements occur. End pulse: The end pulse action sources the idle (or bias) level if the pulse mode is enabled.

The remote trigger model dictates the sequence of operation for the SMU when it is configured to perform a sweep. When the SMU comes to an event detector, it suspends operation and waits for the event you have assigned to the stimulus input. If no event is assigned, the SMU continues uninterrupted past the event detector and through the trigger model. When the SMU comes to an action block, it performs the appropriate action, if enabled. The SMU loops through the arm and trigger layers until the programmed arm and trigger counts are satisfied.

Configuring source and measure actions

You can configure the source action using any of the following functions:

smuX.trigger.source.linearY ()
smuX.trigger.source.logY()
smuX.trigger.source.listY()

Where:

Y = Source function (v = voltage, i = current)

Source functions cannot be changed within a sweep.

To enable the source action, set the smuX.trigger.source.action attribute to smuX.ENABLE.

The source‑measure unit (SMU) can be configured to perform any or all available measurements during a sweep using the smuX.trigger.measure.Y() function. To enable the measure action for a simple synchronous sweep, set the smuX.trigger.measure.action attribute to smuX.ENABLE. To enable the measure action for an asynchronous sweep, set the smu X.trigger.measure.action attribute to smuX.ASYNC.

In asynchronous mode, trigger your measurements before the source completes the sweep (before the end sweep action occurs). If the source loop has completed its end sweep action, the measure loop terminates unless the measure action block is actively measuring. If this is the case, the active measurement is allowed to complete before returning to the arm layer.

For more information about the sweep functions, refer to Sweep operations.

Configured source and measure delays are imposed when the SMU executes the source and measure action blocks. Additionally, if the measure count setting is greater than one, then the measure count is satisfied each time the measure action is performed.

The arm and trigger counts must be set to control how many times the SMU executes the source and measure actions. The arm count indicates the number of times to execute the complete sweep. The trigger count sets the number of loops in the trigger layer. Typically, you set the trigger count to be equal to the number of points in the configured sweep. If the trigger count is not equal to the number of points configured in the sweep, then one of the following occurs:

• If the trigger count is greater than the number of points in a sweep, the SMU satisfies the trigger count by restarting the sweep values from the beginning. The points are configured by the smu X.trigger.source.linearY(), smuX.trigger.source.log Y(), or smuX.trigger.source.listY() command.
• If the trigger count is less than the number of source values configured, the SMU satisfies the trigger count and ignores the remaining source values.

For example, configure a three-point linear voltage sweep from 1 V to 3 V, with the trigger count set to 2. The SMU outputs 1 V, 2 V. If the trigger count is set to 6, the SMU outputs the values 1 V, 2 V, 3 V, 1 V, 2 V, 3 V, repeating the source values twice in a single sweep.

Enabling pulse mode sweeps using the end pulse action

Enable pulse mode sweeps using the end pulse action. The example command below illustrates how to configure pulse mode sweeps by setting the end pulse action:

smua.trigger.endpulse.action = smua.SOURCE_IDLE

You can use timers to configure the pulse width and period (see Timers for more information). To disable pulse mode sweeps, set the smuX.trigger.endpulse.action attribute to smuX.SOURCE_HOLD.