Occasional Frequency Measurement Error Even With Clean Signal

Updated Jul 27, 2018

Reported In

Driver

  • NI-DAQmx

Issue Details

I have a NI-DAQmx frequency task. Usually, I am measuring the proper frequency, but occasionally I see a slight error in the measurement. I have verified that this occurs even with a steady, clean clock signal. How can I fix this?

Solution

The occasional error can most likely be attributed to quantization error. The phase difference between the input signal and the counter timebase can result in the counter missing both edges, missing one and catching one, or catching both edges.

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