There are several different types of thermocouples. Some are suitable for very low temperatures, down to -180°C, and some can be used to measure very high temperatures, up to +1500°C.
The principle for a thermocouple is that when a metal is subjected to a temperature differential, a voltage will develop. A thermocouple uses two wires of different metals, so that two different voltages are generated, and we can then measure the differential, which will be proportional to the temperature difference between the two ends of wire.
The generated voltage is very small – in the order of microVolts per degree – and to know the absolute temperature we also need a reference. The signal from a thermocouple needs to be amplified for the ezeio to be able to measure it. There are several manufacturers of thermocouple interfaces that can supply a suitable output signal for the ezeio system.