Open Lead Alarm

An open lead alarm indicates when Force leads disconnect from Sense leads in a remote sense configuration.

Introduced in TestStand 2023 Semiconductor Module 2024 Q3

Note You must install NI-DCPower 2024 Q3 or later to enable open lead alarm.

In a remote sense configuration, the difference between the output and sense voltages is within a given proximity. NI-DCPower continuously monitors the output and sense voltages and reports disconnected pins to TSM when the difference between the voltages is greater than a threshold.

TSM supports open lead alarms for the following pins on the following hardware models:

Model Pin
Output HI Output LO Sense HI Sense LO
PXIe-4137/9 √ √ — —
PXIe-4147 √ √ — —
PXIe-4162/3 with the PXIe-416xOpen-Sense Protection Accessory √ — — —
PXIe-4162/3 without the PXIe-416xOpen-Sense Protection Accessory √ √ √ √
Note For PXIe-4162/3 without the PXIe-416xOpen-Sense Protection Accessory, when an open lead alarm latches, TSM cannot differentiate between disconnected Output pins and Sense pins.

If you add open-sense protection to PXIe-4162/3 by connecting a resistor between the Output HI and Sense HI pins and between the Output LO and Sense LO pins, TSM supports open lead alarm for the Output HI and Output LO pins.

Considerations for Using Open Lead Alarm

Take the following considerations when using open lead alarm:

  • When Force leads disconnect from Sense leads, open lead alarm may not latch if the current level or current limit of the instrument channel is less than 1 mA.

    In this case, compliance alarm may latch to indicate an issue with the remote sense configuration.

  • While PXIe-4139 allows up to 3 V lead drop per lead, a lead drop greater than 1.5 V may trigger an open lead alarm on PXIe-4139.

    To avoid false open lead alarm, NI recommends designing your application circuitry to ensure that the lead drop per lead does not exceed 1.5 V and/or configuring the instrument driver to use a slow transient response.

  • PXIe-4162/3 and PXIe-4147 share LO between channels.

    Disconnecting some but not all Output LO connections may suppress open lead alarm.

Note Refer to SMU Best Practices: Understanding Compliance and Device Protection Errors for additional information and guidance about SMU usage. Refer to the Overload Protection section of the user documentation for your SMU model for information about overload protection features.