PT100 resistance temperature detectors (RTDs) are widely utilized in industrial production due to their high accuracy, wide measurement range, and robust construction. To ensure system stability, it is essential to understand common fault signatures and their respective solutions.

1. Indicated Value Lower Than Actual or Unstable

Possible Causes: * Accumulation of metal shavings, dust, or moisture between the terminals, causing a “leakage” or partial shunt.

Internal moisture or light contamination within the protective sleeve.

Solutions: * Clean the terminal block and remove any dust, water droplets, or debris.

Locate potential partial short-circuit points and strengthen the insulation.

Dry the internal components if moisture is present.

2. Drift in Temperature-Resistance Relationship

Possible Causes: * The platinum wire material has undergone corrosion, oxidation, or chemical deterioration due to long-term exposure to harsh environments.

Mechanical stress or contamination of the sensing element.

Solutions: * Replace the PT100 element. Once the physical properties of the platinum wire are compromised, the sensor can no longer be calibrated effectively.

3. Display Instrument Shows a Negative Value

Possible Causes: * Short circuit: A direct short in the RTD element or the lead wires results in near-zero resistance, which the meter interprets as an extremely low (negative) temperature.

Incorrect Wiring: Reversed polarity or incorrect connection in a 3-wire/4-wire bridge circuit.

Solutions: * Verify and correct the wiring sequence between the sensor and the instrument.

Inspect the lead wires for insulation breakdown; locate the short circuit and re-insulate.

4. Display Instrument Shows Infinite Readings (Overflow)

Possible Causes: * Open Circuit (Breakage): The platinum wire element is broken, or a lead wire has snapped.

Loose Connections: Wiring terminals have become loose due to vibration or oxidation.

Solutions: * Check for continuity using a multimeter. If the element is broken, replace the RTD.

Tighten all terminal screws and re-solder any disconnected joints.