What is the AUX input used for on NI-DMM Modules? - KnowledgeBase - Support

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What is the AUX input used for on NI-DMM Modules?

Hardware: Modular Instruments>>Digital Multimeters (DMM)>>PCIe-4065, Modular Instruments>>Digital Multimeters (DMM)>>PCI-4065, Modular Instruments>>Digital Multimeters (DMM)>>PXI-4072, Modular Instruments>>Digital Multimeters (DMM)>>PCI-4060, Modular Instruments>>Digital Multimeters (DMM)>>PXI-4071, Modular Instruments>>Digital Multimeters (DMM)>>PCI-4070, Modular Instruments>>Digital Multimeters (DMM)>>PXI-4070, Modular Instruments>>Digital Multimeters (DMM)>>PXI-4060, Modular Instruments>>Digital Multimeters (DMM)>>PC-4060, Modular Instruments>>Digital Multimeters (DMM)>>PXI-4065

Problem:
I am looking into purchasing a National Instruments DMM Module and I would like to know what the AUX connector actually does. Do I need it?

Solution:

The Auxillary (AUX) connection on the Front Panel of an NI-DMM is used to extend the connectivity of the device in order for it to communicate with signals and devices independent of the PXI System or PC it may be housed in.

There are two main uses for the AUX connector:

1. SCXI Switch Module Control

Because DMMs have great accuracy and resolution specifications they are limited in channel count. By using a Switch/DMM configuration, the channel count can be increased to a user defined number by using switches to route signals to the DMM.

More information about this can be found in Switch/DMM Hardware Configurations in the related links and the NI-DMM & NI-Switch help files.

2. External Triggering or Handshaking with NI & 3rd Party Devices

To be able to provide your own trigger source to the DMM, or a number of DMMs (if you wish to synchronize them) you could connect this directly to the front panel of the module(s).
Without this external connection to be able to provide an external trigger source you would need use another device in the PXI system, perhaps a Multifunction DAQ board, to be able to route this external trigger to the PXI backplane which the DMM would then reference. The AUX trigger becomes particularly useful when synchronizing a number of DMMs within a PC. Without the AUX connector on the front panel it is more difficult to share a common trigger signal between DMMs in a PCI setup. The way that this can be achieved is explained in Configuring a PCI-4070 DMM to Receive a Start Trigger from Another PCI Device, in the related links.

The AUX connector consists of 9 Pins.

Pin Assignment :

When using external triggering and handshaking

2 Ground
3 AUX Trigger In
6 Measurement Complete (MC)
9 External Trigger In (Trigger/Sample Trigger)

SCXI communication

1–5, 7–9 SCXI Communication

National Instruments provides different cable solutions to interface with the AUX connection. See Multi-module Scanning with National Instruments Switches in the related links for more information on how to use these different cables.

Attachments:

Report Date: 08/02/2007
Last Updated: 09/05/2007
Document ID: 4C14KIB4

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