NI-9361 Frequency Measurement Returns Last Value Instead of 0Hz

Updated May 6, 2023

Reported In

Hardware

  • NI-9361

Software

  • LabVIEW FPGA Module
  • LabVIEW

Driver

  • NI-DAQmx

Issue Details

I am using a NI-9361 in a cDAQ or cRIO chassis. I am reading the signal correctly until I expect the value to be 0Hz. When this occurs, I observe that the channel appears to return a previous value. Why is this occurring and how can I fix it?

Solution

The Maximum Measurable Period is the property responsible for this behavior. This feature makes the counter return a measurement value of 0Hz when the input signal period is larger than this value. When the value of this property is set to zero (default), the feature is disabled. This keeps the counter measuring until a valid measurement is detected, the counter overflows, or the user stops the counter.
 

CompactDAQ Chassis

Place a DAQmx Channel Property Node as indicated by the image below. To find the property, navigate to Counter Input » General Properties » More » Advanced » Maximum Measurable Period. Set the Maximum Measurable Period to the desired period you wish to receive updated signals.

 

CompactRIO Chassis (FPGA mode)

To fix the behavior you are observing, first confirm that the Measurement Mode is set to Period. Then, set the Maximum Measurable Period to the desired period you wish to receive updated signals. You can set this value in the Module Properties.

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