Sewage electromagnetic flow meters play a crucial role in wastewater management, offering precise and reliable flow measurement. However, like all industrial instruments, they may occasionally malfunction—particularly when the display shows no flow. This article outlines common causes of such issues and offers practical solutions to ensure accurate and uninterrupted measurement.

Common Reason 1: No Display or Signal Output

Causes:

  • Power supply is disconnected or unstable
  • Blown fuse or incorrect power voltage
  • Damaged sensor components
  • Improper cabling or loose connections
  • Fluid does not fully fill the pipe
  • Internal parts or electrodes are covered with deposits

Solutions:

  • Check if the power is connected and voltage is within required range. Replace the power board if needed.
  • Inspect fuses and power circuit board outputs.
  • Verify the signal cable is properly connected and undamaged.
  • Ensure the pipe is full of liquid and the flow direction matches sensor settings.
  • Clean sensor electrodes if scale or sediment is present.
  • If necessary, send the converter back to the manufacturer for inspection.

Common Reason 2: Fluctuating Output Signal

Causes:

  • Pipeline vibrations
  • Air bubbles in the liquid
  • External electromagnetic interference (e.g., welding equipment nearby)
  • Loose or misaligned circuit board

Solutions:

  • Confirm if flow fluctuations are due to actual process conditions or pulsed flow.
  • Check for external electrical noise and ensure proper grounding.
  • Ensure pipe is full and free of air bubbles; consult process engineers.
  • If vibration is present, secure internal boards to avoid contact issues.

Common Reason 3: Measured Flow Does Not Match Actual Flow

Causes:

  • Faulty transmitter board
  • Presence of tiny air bubbles in low-flow liquid
  • Loose or deteriorated signal cable
  • Incorrect converter settings

Solutions:

  • Inspect the transmitter board for water ingress or corrosion. Replace if damaged.
  • Keep the flow rate above the minimum threshold to avoid signal distortion.
  • Replace or reconnect insulation-degraded signal cables.
  • Re-calibrate the converter’s zero and span values to ensure accuracy.

Common Reason 4: Output Signal Exceeds Full-Scale Range

Causes:

  • Incorrect signal wiring or disconnected cable
  • Parameter mismatch between converter and sensor
  • Improper converter configuration

Solutions:

  • Reconnect the signal wiring properly and check for continuity.
  • Verify sensor and converter compatibility; replace mismatched units.
  • Reset the converter’s configuration and calibration values.

Common Reason 5: Unstable Zero-Point

Causes:

  • Incomplete filling of the pipe or presence of gas bubbles
  • Slight fluid movement when pump is presumed off
  • Dirty electrodes or non-uniform fluid conductivity
  • Insulation failure in signal circuit

Solutions:

  • Ensure the pipeline is fully filled and free from gas entrainment.
  • Recognize that minor flow movement is normal and not a fault.
  • Clean electrodes and inner pipe if contamination is detected.
  • Check and restore insulation in terminal blocks or signal paths.

Final Thoughts

A sewage electromagnetic flow meter not displaying flow could stem from a variety of electrical, mechanical, or operational causes. By methodically checking power supply, cabling, sensor conditions, and flow parameters, most issues can be quickly resolved. For persistent or unclear faults, seeking manufacturer assistance or professional service is advised.

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FAQs

Q1: What is the first step when my flow meter shows no reading?
A: Always begin by checking the power supply and verifying all connections are secure.

Q2: Can external electromagnetic interference affect readings?
A: Yes, nearby heavy machinery or welding equipment can disrupt flow meter signals.

Q3: How often should I clean the electrodes?
A: Cleaning frequency depends on the fluid characteristics. For sludge or high-solid sewage, monthly inspection is recommended.

Q4: Do air bubbles affect measurement?
A: Yes, especially in low-flow conditions. Bubbles can cause unstable signals or inaccurate readings.