PRACTICAL THERNMOMETERS

Some common liquid-in-glass thermometers include:

Thermocouple Thermometers
A thermocouple thermometer consists of two wires made of different metals where the ends of the two wires are joined together to form two junctions. If the two junctions are at different temperatures than the greater the difference the, then greater the e.m.f. produced across the ends of the two junctions. One junction is kept at a constant temperature so the other junction can be used to act as a probe to measure temperatures other than the fixed temperature.
Advantages:
1) Measure a very large temperature range of -200°C to 1500°C.

2) As the wire junctions are very small, the thermometer can be used to measure temperatures at a point.

3) Due to its low thermal capacity it is very responsive to rapidly changing temperatures. The low thermal capacity is due to its small mass and because of the metals conductivity.

4) As the output is an electrical signal, it can be connected to suitable electrical equipment for checking rapid or sudden temperature changes.