Unexpected Trigger Delay with DMM in Waveform Acquisition Mode

Updated Dec 17, 2018

Reported In

Hardware

  • Digital Multimeter Device

Driver

  • NI-DMM

Issue Details

When setting up a triggered waveform acquisition using an NI-DMM device, I see a latency of >1ms between the trigger signal and first sampled point of my waveform.  The specifications document states a much smaller trigger latency.  Why am I seeing this added delay?

Solution

Even when using the DMM in waveform acquisition mode, there are properties related to DMM acquisition that will affect your trigger latency.  The graphic below shows the normal DMM measurement cycle:

The only differences in the measurement cycle for a DMM acquisition and waveform acquisition are that a waveform acquisition does not allow ADC Calibration and the aperture time is replaced with waveform sampling.  To get the lowest trigger latency possible, turn off AutoZero and set your Settle Time to zero for the acquisition.

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