How would you identify a bad sensor in a control loop?

How would you identify a bad sensor in a control loop?

• A. Check sensor output against reference, verify wiring, swap with known-good sensor, and observe system response
• B. Replacing the entire controller
• C. Ignore sensor readings and rely on setpoint only
• D. Disconnect the sensor and run system without feedback

Answer: (A)

In a control loop, diagnosing a bad sensor relies on validating the sensor signal against a known reference, checking wiring and power, and confirming with a swap to a known-good unit while watching the system response. Start by comparing the sensor output to a calibrated reference or a trusted measurement of the same process variable; a persistent discrepancy suggests the sensor or its front-end is off. Then inspect all wiring, connectors, and power supply to rule out loose connections, corrosion, grounding issues, or incorrect supply that could cause erroneous readings. If the issue still isn’t clear, swap in a known-good sensor and observe how the system behaves: if the process variable now tracks correctly and the control action stabilizes as expected, the original sensor was faulty. This approach uses the feedback loop itself to verify sensor health and avoids unnecessary changes to the controller or operating the system without feedback.

In a control loop, diagnosing a bad sensor relies on validating the sensor signal against a known reference, checking wiring and power, and confirming with a swap to a known-good unit while watching the system response. Start by comparing the sensor output to a calibrated reference or a trusted measurement of the same process variable; a persistent discrepancy suggests the sensor or its front-end is off. Then inspect all wiring, connectors, and power supply to rule out loose connections, corrosion, grounding issues, or incorrect supply that could cause erroneous readings. If the issue still isn’t clear, swap in a known-good sensor and observe how the system behaves: if the process variable now tracks correctly and the control action stabilizes as expected, the original sensor was faulty. This approach uses the feedback loop itself to verify sensor health and avoids unnecessary changes to the controller or operating the system without feedback.