DESCRIBE the two alternate methods of determining temperature when the normal temperature sensing devices are inoperable.
The dual-element RTD has two sensing elements, of which only one is normally connected. If the element in use becomes faulty, the second element may be connected to provide temperature indication.
If an installed spare is not utilized, a contact pyrometer (portable thermocouple) may be used to obtain temperature readings on equipment or systems that are accessible.
If the malfunction is in the circuitry and the detector is still functional, it may be possible to obtain temperatures by connecting an external bridge circuit to the detector. Resistance readings may then be taken and a corresponding temperature obtained from the detector calibration curves.