Configure an External SMU

How to Configure a SMU

1. Important: Create an SMU by name (one-time). Learn how (separate topic).

2. On the Configure an External Device dialog, click Device Properties. (This topic).

Using Hardkey/SoftTab/Softkey

Using a mouse

1. Press Setup > External Hardware > External Device...

1. Click Instrument

2. Select Setup

3. Select External Hardware

4. Select External Device...

Once configured, set the SMU source voltage and display Voltage / Current Meter measurements:

• SMU Sources:  DC Source control is available in Standard and Gain Compression/GCX channels.  Set the Start and Stop voltage on the DC Control dialog. To access this dialog:

• • Press Sweep > Source Control > DC Source....

• SMU Measure:  DC measurements are available in Standard and Gain Compression/GCX channels.

• • In Gain Compression /GCX channels, display DC parameters as you would an RF parameter, by pressing Trace > Trace Setup > Measure....

  • In a Standard channel, configure an unratioed measurement. Press Trace > Trace Setup > Measure... > Receivers. For Numerator, select the external (or internal) DC meter.

  • Change the X-axis to display the DC Meter parameters by pressing Sweep > Main > X-axis Type, then select the DC Meter.

Note: Gain Compression CSV files contain Voltage / Current settings and measurements

External SMU Configuration - Setup Tab help

To start this dialog, on the External Device Configuration dialog, select SMU as the Device Type. Then click Device Properties.

SMU Information

The DC device names for six DC devices are listed. The names are made from the root device name (given in the External Device Configuration dialog) plus a suffix.

In the above image (example):

• Device0 is the root device name.

• “_Src1” means voltage source of channel 1.

• “_VM1” means voltage meter of channel 1.

• “_AM2” means current meter of channel 2.

• Check Chan <n> to enable that channel in the SMU device.

Trigger Settings

Trigger Mode: Choose from:

• Software CW (GPIB)  Slowest method. The SMU receives each stimulus voltage from the VNA over GPIB, USB, or LAN. No other trigger cables are required.

• Hardware List (BNC)  Available ONLY in B2900 series. Fastest method. The SMU receives a list of stimulus voltages from the VNA, then receives trigger signals though a rear-panel connector when appropriate from the VNA.

Note: The B2900 series can store no more than 2500 data measurements. Therefore, this mode is NOT allowed when the VNA data points exceed 2500 points.

Note: Hardware List trigger mode is NOT supported in GCA 2D sweeps.

• SMU Trigger In / Out - Available ONLY when the trigger mode is Hardware List. Select the trigger in and trigger out pins on the B2900 digital I/O connector. Connect these pins to the either pair of VNA AUX IO IN and OUT connectors. The VNA AUX trigger pair is automatically selected.

External SMU - Source / Voltage / Current Meter dialog box help

The descriptions for this dialog pertain to the Source, Voltage, and Current Meter tabs. Exceptions are highlighted.

SMU Chan  Select the SMU channel for which the settings on this page apply.

Source type (Source ONLY)  Select either a voltage source or current source.

Device Settings

Timeout - Sets a time limit for the DC source or meter to make contact with the VNA. If this time limit is exceeded, the VNA stops the measurement and displays the following error message.

EXECUTION ERROR;OPC QUERY TIMEOUT ERROR

If this occurs, check the connections between your VNA and external device.

Dwell Before Sweep  Wait time before making a sweep.

Dwell After Point

• Source  Wait time after setting the voltage/current at each data point.

• Voltage / Current Meter  Wait time before measuring voltage/current at each data point.

Current / Voltage Limit  (Source ONLY Depends on the Source Type selection) Sets the maximum current or voltage to be allowed from the source.

Note: To change the X-axis to display the Meter units, click Response, then Display, then Labels, then Select X-Axis, then select the SMU Meter.

Receiver / Source Correction

• For a Source, use the correction settings to scale and offset the output voltage or current.

• For a Voltage or Current Meter (receiver), use the correction settings to display and scale measurements.  For example:

Measure the voltage across a 5 ohm resistor, then display the results in A(mperes).

Using ohms law,  I = V / 5 ohms or I = V *.2

For receiver correction, enter Scaling = .2; Offset = 0.

ON  Check to apply the following correction factors to each measurement.

Offset: Enter the value to offset the Meter reading or set the Source voltage.

Scaling: Enter the value to scale the Meter reading or set the Source voltage.

Displayed Output = (Measured / Set value - Offset) * Scaling value.

Edit Commands - Click to start the Edit Commands dialog. This feature is usually not necessary with an SMU external device.

Save - Press to save the edited SMU configuration to an *.xml file. The list of files is NOT filtered so use a descriptive filename.

Load - Press to load an existing configuration.

Edit Commands dialog box help

The SMU Source and Meter Edit commands are almost identical in how they operate. Both are documented here.

Global Tab

The Global tab includes the system settings for the SMU Source.

ID Query - Enter the SCPI command to return the ID string of the DC Source. Typically *IDN? This entry can be left blank.

Error Query - Enter the SCPI command that is used to return DC Source errors. Typically SYST:ERR?

Enable I/O - Enter the SCPI commands that is used to enable the DC Source to output voltages.

Disable I/O - Enter the SCPI commands that is used to disable the DC Source from outputting voltages.

Maximum / Minimum DC Output  (Source ONLY)

Read Max / Min Using - Select, then enter the commands used to return the output limits of the SMU source.

Define Max / Min As - If the SMU has no commands to return these values, or you would rather define the limit for your SMu, then enter the Max and Min voltage limits.

Test Connection

Click to start the Test Connection dialog. You must first have entered the I/O Configuration settings  and select Enable IO on the External Device dialog.

Enter a SCPI command, then click Send or Send&Read when a return value is expected.

Sweep Tab

Use the Sweep Tab to send SCPI commands to the SMU at the beginning or end of each sweep.

Abort Sweep - Enter the SCPI command that is used to Abort or reset the SMU. This would be necessary when the VNA sweep is aborted or terminated. The VNA will then send the command to the SMU.

Point Tab

Read (commands) - Enter the SCPI command that is used to make a DC measurement at each data point.

Set (commands) - Use <%variable> to make a DC Meter setting.