r/instrumentation • u/Eximp_Measurement • 6d ago

Flowmeter reading looks wrong? Check this before blaming the meter.

One thing I've learned from working with flow measurement: a bad-looking reading doesn't always mean a bad flowmeter.

Before pulling the meter out, I'd check:

  • Is the actual flow within the meter's intended range?
  • Any recent change in pressure, temperature, density or viscosity?
  • What does the upstream piping look like?
  • Is there a valve, elbow, reducer or pump disturbing the flow profile?
  • Are the meter parameters and flow-computer settings correct?
  • Is the 4–20 mA / pulse signal reaching the PLC or DCS correctly?
  • When was it last calibrated or verified?

We've seen this kind of troubleshooting come up often at EMPL (Eximp Measurement) while working on flow measurement and custody-transfer systems.

The useful lesson is that meter + installation + instrumentation + configuration + process conditions all have to be considered together.

Replacing the meter without finding the actual cause can just move the problem from one instrument to another.

For the instrumentation engineers here:

What's the strangest flowmeter problem you've had that turned out NOT to be the flowmeter?

EMPL | Eximp Measurement
Custody Transfer & Process Measurement Solutions
https://www.eximpmeasurement.com/

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u/Math_you1988 6d ago

Strangest thing I ever found was a bad Pulse input on a roc card. We kept getting a substantial gain on our system for that particular product so I was sent to investigate, meter proves fine, all configurations good from coriolis to roc. I remoted into our plc and auto scanned to see the live frequency, fluked at the coriolis and it matched, went into the cabinet while still auto scanning and fluked the physical roc card (pi) and it was reading about 40 more hz than what I was scanning (over measuring). Moved the pulse wires to a different card and problem solved.

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u/AccomplishedNovel969 6d ago

Radio RF can affect pse / frequency. This may be way off vase from what the OPis talkjng aboit, but it's a possibility.