Inaccurate Flow Measurement in Electromagnetic Flow Meter


  • The flow meter reading is erratic or significantly deviates from the expected flow rate.
  • The flow meter shows zero flow when there is actual flow in the pipe.
  • The displayed flow rate fluctuates rapidly.

Ok, as i see the picture, i suppose that you’re talking about a Promag. So, many causes here:

  • someone has initiated an “Empty calibration” with a non-empty pipe. You have to do that first. Make sure that the pipe is really empty; the flowmeter has 4 detectors inside. No one must touch the water. And start the calibration.
  • Because, if your “empty cal” is made with water of something else (conductive) whenever there is a flow, the Promag only see 0.
  • Make sure the fluid passing inside is conductive, depending on your model, you must be > 100µS
  • Make sure the probes (inside the flow meter) in contact with water are clean.
  • Activate the Detection of Product. in French: DPP. Don’t know the real term in English menus. When this function is activated, if your pipe goes empty or small level of fluid inside. The calculator force 0 on the display. So your flowmeter won’t fluctuate randomly.

Something else, I hope that your pipes are conductive (metal…) and linked to the ground. If not (plastic, fiber or PVC pipes.) you’ll need a circular ground plate to install between your flowmeter and the pipe. To create the electrical loop. Without that, no measure or random values.