Why Doesn't My NI-407x DMM Respond to Input Triggers?Hardware: Modular Instruments>>Digital Multimeters (DMM)>>PXI-4070, Modular Instruments>>Digital Multimeters (DMM)>>PCI-4070, Modular Instruments>>Digital Multimeters (DMM)>>PXI-4072, Modular Instruments>>Digital Multimeters (DMM)>>PXI-4071
Problem: I'm trying to trigger my NI-407x Digital Multimeter, but the trigger either incrementally or never registers in hardware. What do I need to do to guarantee the NI-407x DMM triggers? Solution: The guaranteed minimum input trigger pulse width for NI-407x DMMs is 1us (with a cable less than 2 meters). This minimum pulse requirement is longer than many other National Instruments cards. If DMM trigger pulses are less than 1us, the DMM will either intermittently or never trigger. This issue can occur when using a DMM in handshaking mode or when synchronizing with other cards. The easiest way to determine an unknown trigger pulse width is to connect the trigger source to an oscilloscope and measure the pulse width. If the pulse is less than 1us, we can run the pulse through a counter on a counter/timer or multifunction DAQ board and then run the counter output to the DMM. Since counters can trigger reliably with much smaller pulse widths (e.g. 50ns on the 6602), we simply need to set up a retriggerable digital pulse task. This task must generate a long (over 1us) digital pulse each time the input trigger source receives a pulse.  There's an excellent example on how to set up this counter task located in the Example Finder (Help»Find Examples»Hardware Input and Output»DAQmx»Generating Digital Pulses»Gen Dig Pulse-Retriggerable.vi). Related Links: KnowledgeBase: PXI-407x DMM Synchronization Q&A DeveloperZone: DMM and Switches Synchronous and Handshaking Scanning Examples Attachments:
Report Date: 06/18/2009 Last Updated: 06/19/2009 Document ID: 4YHFMBG0 |
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