A temperature monitoring system

A temperature monitoring system for use with a thermocouple and a heater controller to control a heater, wherein the system comprises:

• a differential amplifier which comprises:
• a first input terminal which is configured to connect to a first terminal of the thermocouple;
• a second input terminal which is configured to connect to a second terminal of the thermocouple;
• and
• an output terminal which is configured to provide a temperature sense signal to the heater controller to control the heater, wherein the differential amplifier is configured to generate the temperature sense signal in response to a difference between a first voltage at the first input terminal and a second voltage at the second input terminal, wherein the system further comprises:
• a protection circuit which is connected to the first input terminal and the second input terminal, the protection circuit being configured to operate in:
• a first mode in the event that a leakage current flows into the first input terminal or the second input terminal;
• and
• a second mode in the event that a leakage current flows out from the first input terminal or the second input terminal,
• wherein, in the first mode or the second mode, the protection circuit controls the differential amplifier to output a temperature sense which controls the heater to operate at a temperature at or below a predetermined temperature to reduce the risk of damage being caused by the heater.