DMM_Scan PXI Relay Driver 32V-16C Library

The DMM_Scan PXI RLY Driver 32V-16C 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 combined with a single SWITCH individual relay driver used to execute both MUX and SWITCH Shunt Relay functions.

This library is intended to perform a specific scan configuration in random order for a combined maximum of 32 voltage type and 16 current type measurements in a 2-wire (differential) configuration.

This library supports 32 voltage type differential measurements and 16 current differential measurements.

Recommended Hardware

  • PXI chassis (hybrid) and controller
  • PXI-4065 or PXIe-408x DMM
  • PXI-2567 (or similar relay driver module) to execute both multiplexer and current shunt functions using dual-pole external relays.

Recommended Hardware Configuration

This section outlines the recommended connections, using the recommended PXI-2567 or similar relay driver module configured in a mapped topology:

  • 32 voltage-based 2-wire measurements (ch0 to ch31) connected to the DMM HI/LO
  • 15 current-based 2-wire measurements (ch32 to ch47) connected to the same DMM to CURRENT/LO
  • Current shunt channels on the remaining channels (ch48 to ch63) of the switch relay driver.
    Note To simplify connections and ensure DUT power continuity through all measurements, map the shunt channels in the same order as the current measurement channels. With this mapping, the shunt channel number is always equivalent to the current measurement channel number + 16.


Notice Do not make any connection to reserved pins. Consult the specifications and documentation for your device for more information about pin connections.

The following figures illustrate example connections for a DMM SCAN using the PXI-2567.





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 for the Initialize VI. The DUT does not receive power because all shunt relays are open.

Library VI Descriptions

The DMM_Scan PRD 32V-16C 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 PRD 32V-16C Initialize VI randomly defines a specific switch topology with a fixed channel mapping for the 32 (maximum) voltage and 16 (maximum) current measurement configuration. Each current channel is linked to the shunt channel according to the following pattern: shunt channel number = current measurement channel number + 16. For example, current ch32 is linked to shunt ch48.

Enable the Close all Shunts control to close all shunt relays from channels 48 to 63 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.

Use the Relays Debounce Time (ms) control to define the debounce timing specifications for external relays. The typical default value is 5 ms. Adjust the value for your specific external relay. Values that are too small introduce errors in measurements accuracy.

If the NI multiplexer uses embedded relays the DMM_Scan PRD 32V-16C Initialize VI returns the switch maximum voltage and current characteristics from each multiplexer and shunt relay. For external custom relays and the NI 2567 Relay Driver, the return values are 0.

The DMM_Scan PRD 32V-16C 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—Specifies 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. Refer to Default Values and Automatic Range Coercion for more information about listed ranges.

    • The DMM_Scan PRD 32V-16C 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 PRD 32V-16C 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: