DMM_Scan PXI Mux PXI Shunt 16V-15C Library

The DMM_Scan PXI Mux PXI Shunt 16V-15C Library VIs initialize, configure, scan, and measure a list of channels from multiple DMM functions, as well as close the scan on the NI-DMM, SWITCH MUX, or SWITCH shunt relay instrument.

This library performs a specific scan configuration that is assigned in a random order to a combination of 16 voltage type (maximum) and 15 current type (maximum) measurements in a 2-wire (differential) configuration.

This library supports 16 voltage type differential measurements, 15 current differential measurements, and 15 free SPST relays.

Recommended Hardware

  • PXI chassis (hybrid) and controller
  • PXI-4065 or PXIe-408x DMM
  • PXIe-2527 (or similar multiplexer switch module) with TB-2627 terminal block
  • HV6-BAN4 cable to connect the DMM to the TB-2627 terminal block
  • PXI-2568 or similar relay module with individual SPST relays for the current shunt continuity function

Recommended Hardware Configuration

This section outlines the recommended connections, using the PXIe-2527 or similar multiplexer switch module configured in a dual topology:

  • 16 voltage-based 2-wire measurements (ch0 to ch15) connected to the DMM HI/LO
  • 15 current-based 2-wire measurements (ch16 to ch30) connected to the same DMM to CURRENT/LO


The following figure depicts the connections for the PXI-2568 or similar relay module, as shunt, dedicated to 15 current-based 2-wire measurements (ch16 to ch30). Use a configuration in parallel with the current channels to simplify connections and maintain continuity of DUT power during all measurements.



The following figures illustrate example PXI Mux PXI Shunt connections for a DMM SCAN using the PXIe-2527 and PXI-2568.



Software Recommendations

For voltage and current measurements, you must individually declare, in any order, the channels, functions and ranges, and digits in the scan list.

For timing optimization, the software removes the configuration phase between multiplexer scans when sequential channels in the scan list use the same configuration.

By default, all shunt relays are closed by the Initialize VI. This behavior can be disabled with the Close All Shunts control.

To measure only a list of resistances, disable the Close All Shunts control Initialize VI. The DUT does not receive power because all shunt relays are open.

Library VI Descriptions

The DMM_Scan PMPS 16V-15C Initialize VI creates a NI-DMM Scan driver session on each device specified by the Scan Resource Names control. The device uses the specified powerline frequency value to select a timebase for setting the Aperture Time property in powerline cycles (PLCs).

Note The default powerline frequency value is 50 Hz. Specify 60 Hz for North or South America.

By default, the DMM_Scan PMPS 16V-15C Initialize VI randomly defines a specific switch topology with a fixed channel mapping for the 16 (maximum) voltage and 15 (maximum) current measurement configuration. Each current channel number is linked to the equivalent channel shunt number. For example, Current ch16 is linked to Shunt ch16.

Enable the Close all Shunts control to close all shunt relays from channels 16 to 30 in a fixed channel topology mapping and allow continuous power to the DUT during all measurements. disable the control for a 2-Wire Resistance measurement function without any current through the DUT.

The DMM_Scan PMPS 16V-15C Initialize VI returns the maximum voltage and current characteristics from each multiplexer and shunt relay.

The DMM_Scan PMPS 16V-15C Configure and Measure VI configures the NI-DMM Scan measurement list on the resource provided by Scan Resource Handles In based on the following settings:
  • Scan Configuration—Specifes the channel number in the string format chX. Specifies the desired function and range, and the resolution in digits for the measurement. For the best software performance, group channels with the same function types and ranges together.

    • The DMM_Scan PMPS 16V-15C Configure and Measure VI returns the following information.

  • Formatted Measurements—Returns channels, measurements (strings with units), out of range data, and individual measurement times (including configuration, aperture and relay debounce).
  • Raw Measurements—Returns numeric values for use or comparison in a sequencer.
  • Execution Settings and Total Scan Time (s)—Output for optimization, debugging, or reporting purposes.

    • The DMM_Scan PMPS 16V-15C Close VI disconnects all multiplexer and shunt relays, closes the NI-DMM and NI-SWITCH scan sessions associated with the scan resources, and releases all resources.

    The following figure illustrates the minimum usage block diagram, with a loop, for this library.



    The following figure illustrates two sequential DMM scans that use different configurations: