How measure the temperature inside engine cylinder?

To measure the temperature inside an engine cylinder, a thermocouple or a resistance temperature detector (RTD) can be inserted through a hole in the cylinder head or via a spark plug port. These sensors provide real-time temperature readings by converting thermal energy into an electrical signal. Additionally, infrared thermometers can be used for non-contact measurements, though they may be less accurate. It's crucial to ensure that the sensors are properly calibrated and positioned to obtain reliable readings.