Sensor interrogation is a feature of many transmitters today. It can be used to determine whether or not the sensor is working properly by sending a signal through the sensor and monitoring the response. The response will indicate whether the sensor is cracked, broken, clogged or otherwise not operating properly. The transmitter will then display a message indicating the sensor should be checked. For example, a remote operator overseeing a process running at a constant pH of 7 may not have any indication of problems.
However, if the cable is shorted the transmitter will also display approximately pH 7. Without sensor interrogation, or physically checking the system, the operator may think the pH measurement is acceptable when in fact the electrode or cable is damaged, generating a false reading.