Are Both Flow Meter Channels Needed When Measuring One-Directional Flow?

Updated May 3, 2018

Reported In

Hardware

  • Multifunction I/O Device

Issue Details

I am building an application where I read a signal from a VSE V2 type flow meter. I will be using a counter input on my multifunction DAQ device. I know that I will be getting flow only in one direction. Do I still have to read two channels when getting flow only in one direction?

Solution

The flow meter uses a Quadrature Encoder which outputs two square-wave signals slightly shifted to each other. There are two possibilities to measure the meter's output:
  • The typical approach is to use a Quadrature Counter. Such a counter will make use of both of the meter's channels and can detect motion, direction, and position.
  • Using a counter with Edge Detection on one of the meter's output channels is sufficient for basic motion detection.
However, both use cases will use one full hardware counter, so the only advantage of using edge detection over quadrature counting would be saving one signal wired to the input device.

Additional Information

Take into account that the one-channel approach could lead to a reduced movement resolution. E.g. when then flow meter uses X4 encoding: In this mode, each rising and falling edge of both signals correlates with one motion step of the flow meter. Omitting one channel leads to the need to count each detected edge on the remaining channel as two motion steps.

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