Marathon Heater [India] Pvt. Ltd. Manufactures Heater with Thermocouples. Marathon Heater [India] Pvt. Ltd. Manufactures Temperature Sensors, High Quality Heaters etc. The Heater with Thermocouples can be installed to monitor part temperatures. A thermocouple mounted against the heater sheath in the centre of the heater gives a good approximation of block temperature, especially when there is a good fit between the heater and the block. A thermocouple mounted in the tip is useful for monitoring liquid temperatures, or material flowing past the end of the heater.