What type of sensor is used to monitor EGT?

The correct choice is a pyrometer, which is specifically designed to measure high temperatures, making it ideal for monitoring exhaust gas temperature (EGT) in an engine. EGT is a critical parameter in engine performance as it helps in diagnosing engine health, preventing engine knock, and optimizing fuel efficiency. The pyrometer operates by detecting the thermal radiation emitted by the exhaust gases and provides an accurate temperature reading.

Other sensors mentioned, such as piezometers, potentiometers, and capacitance sensors, serve different purposes. Piezometers measure fluid pressure, potentiometers are used for position sensing and voltage control, and capacitance sensors detect changes in capacitance related to proximity or level measurement. None of these sensors are suitable for measuring the extreme temperatures associated with engine exhaust gases, which is why the pyrometer is the correct choice for monitoring EGT.