Hands holding multimeter probes on motor wiring terminals
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Testing a powered three-wire sensor: supply, ground and signal (Hall, flow meter, pressure, turbidity)

Three-wire sensors have electronics inside and cannot be judged with an ohmmeter. The board supplies a DC voltage and ground, and reads a signal back. Test in that order at the sensor connector: supply, ground, signal. Missing supply points to the board or harness, not the sensor.

Cross-checked ~30 min moderateBrands: All

Before you start

  • The sensor side is low-voltage DC, but the board it plugs into may carry line voltage; back-probe carefully.
  • Unplug the appliance before connecting or disconnecting sensor plugs.

Diagnostic steps

Unlock all 8 steps with expected values

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OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work.

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Testing a powered three-wire sensor: supply, ground and signal (Hall, flow meter, pressure, turbidity) · OnCall Tech