Keysight 34401A DMM Measurement

Keysight 34401A DMM Measurement

This is a MeasurementLink example that performs a DMM measurement using an HP/Agilent/Keysight 34401A DMM.

Features

• Demonstrates how to write a MeasurementLink plug-in that uses instrument drivers and NI-VISA
• Pin-aware, supporting a custom instrument type and a single session/pin/site
• Includes InstrumentStudio project file
• Includes a TestStand sequence showing how to configure the pin map, register instrument resources with the session management service, and run a measurement
  • For the sake of simplicity, the TestStand sequence handles pin map and session registration and unregistration in the Setup and Cleanup sections of the main sequence. For Test UUTs and batch process model use cases, these steps should be moved to the ProcessSetup and ProcessCleanup callbacks.
• Demonstrates how to share instrument resources with other measurement services when running measurements from TestStand, without using NI gRPC Device Server
• Demonstrates how to cancel a running measurement by calling the instrument driver's Device Clear VI to halt the measurement in progress
• Demonstrates how to use a LabVIEW UI that has external dependencies (dependencies not available in the LabVIEW runtime)

Required Driver Software

• LabVIEW 2021 or later
• NI-488.2 and/or NI-Serial
• NI-VISA 2024 Q1 or later
• Agilent 34401 LabVIEW Plug-and-Play (project style) Instrument Driver

Required Hardware

This example requires an HP/Agilent/Keysight 34401A or compatible DMM.

By default, the pin map included with this example uses the resource name GPIB0::22::INSTR, which matches the 34401A's factory default address when connected via GPIB. If this doesn't match your configuration, edit [Keysight 34401A DMM Measurement.pinmap](./Keysight 34401A DMM Measurement.pinmap) and replace GPIB0::22::INSTR with the desired resource name (e.g. ASRL1::INSTR or a custom alias).

Using a LabVIEW UI with External Dependencies

This example uses a LabVIEW UI with external dependencies. In order to display the LabVIEW UI in InstrumentStudio, you must first build the Keysight 34401A DMM Measurement UI packed library build specification. The packed library and its containing directory will have all of the dependencies that the UI needs to load in InstrumentStudio.

If you make changes to Measurement UI.vi, you must rebuild the packed library.

Session Management

This example has a slightly different approach to session management than the examples for NI PXI modular instruments.

The examples for NI PXI modular instruments use the NI gRPC Device Server to share a single driver session between multiple operating system processes. When running measurements outside of TestStand, each measurement re-initalizes the instrument. When running measurements in TestStand, the ProcessSetup callback initializes the instrument once per sequence execution, which avoids the overhead of re-initializing the instrument for each measurement.

This example does not use NI gRPC Device Server. The measurement logic and TestStand code module open and close instrument sessions as needed in multiple operating system processes. However, the instrument initialization behavior is the same as before: outside of TestStand, each measurement re-initializes the instrument; in TestStand, the ProcessSetup callback initalizes the instrument once per sequence execution. This approach works for instruments connected via GPIB or serial because multiple processes (TestStand, multiple measurement services) can connect to the same instrument without resetting any instrument state.

In both cases, the ProcessSetup callback registers the instrument with the session management service, the measurement logic uses the session management service to reserve and unreserve the instrument, and the ProcessCleanup callback unregisters the instrument with the session management service. This ensures that only one measurement at a time has access to the instrument.