Common RTD faults include inaccurate readings caused by calibration drift, wire resistance affecting the measurement (especially in 2-wire circuits), electrical noise from nearby equipment, and lead wire connection issues; solutions typically include regular recalibration, utilizing 3-wire (or) 4-wire configurations that compensate for lead wire resistance, proper shielding to reduce noise, & ensuring secure connections at the sensor terminals.
Common RTD Faults
1). Inaccurate Readings
2). Open Circuit (or) No Signal
3). Slow Response Time
4). Drift In Readings
5). Short Circuit
6). Non-Linear Output
7). Mechanical Damage
8). Signal Interference for Long Cables
1). Inaccurate Readings
Cause
- Calibration drift occurs as a result of aging or continuous exposure to high temperatures.
- Wire resistance affects measurement (particularly in 2-wire RTDs).
- Electric noise from neighboring machinery.
Solution
- Periodically calibrate the RTD.
- To prevent wire resistance effects, use a three- or four-wire RTD arrangement.
- Shield the RTD & its wiring to reduce electrical noise. Twisted-pair wires provide improved noise immunity.
2). Open Circuit (or) No Signal
Cause
- Broken or broken sensor element, or lead wires.
- Terminals and wiring have loose connections.
Solution
- Inspect and repair any broken sensors or wiring.
- Ensure that all connections are secure & in good shape.
3). Slow Response Time
Cause
- RTD does not make proper thermal contact with surface (or) medium being monitored.
- Excessive lag owing to protective sheath (or) housing.
Solution
- To improve thermal contact between the sensor and the surface, consider using thermal paste or correct installation.
- Utilize a smaller (or) thinner RTD to get a faster response.
4). Drift In Readings
Cause
- Temperatures higher than the RTD’s rating.
- The platinum element became contaminated as a result of faulty sealing.
Solution
- Utilize RTDs rated for the higher temperatures if necessary.
- Ensure that the sensor is properly sealed to avoid contamination.
5). Short Circuit
Cause
- Moisture infiltration is causing insulation deterioration.
- Damaged insulation between the RTD wires (or) leads.
Solution
- Use RTDs with appropriate ingress protection (IP-rated sensors) for the environment.
- Check your insulation on a regular basis and replace any broken components.
6). Non-Linear Output
Cause
- RTD creates a non-linear resistance-temperature relationship.
Solution
- Apply appropriate signal conditioning and linearization (for example, utilizing a Wheatstone bridge (or) microcontroller with the RTD-specific compensation algorithms).
7). Mechanical Damage
Cause
- Physical stress, vibrations, or inappropriate handling.
Solution
- Use sturdy RTD designs in difficult settings.
- Ensure correct mounting to avoid strain (or) vibration damage.
8). Signal Interference for Long Cables
Cause
- Voltage drop (or) noise pickup in the long RTD signal lines.
Solution
- To adjust for cable resistance, use four-wire RTD designs.
- To avoid signal loss, consider using 4-20 mA loops or digital protocols (such as HART or Modbus).
By addressing these difficulties through correct design, installation, and maintenance techniques, RTD performance & reliability can be considerably enhanced.
You can also follow us on AutomationForum.co, Facebook and Linkedin to receive daily Instrumentation updates.
You can also follow us on ForumElectrical.com , Facebook and Linkedin to receive daily Electrical updates.