Working Principle
ISG fluid level sensors use the non-linear properties of doped silicon to detect a liquid or excessive heat in conjunction with a current limiter and heat sink. As the temperature of the sensor changes, so does the voltage across it, functioning as a thermally variable resistor.
The sensor generates heat at its tip, which is removed by the surrounding fluid as rapidly as it is created, keeping the device in a high impedance state. Once the sensor tip is removed from contact with the surrounding fluid, the element heats up and drives the sensor impedance down. This change in state is reflected as a change in the voltage drop, providing a clear signal indicating fluid presence or absence.
