Thermocouple Thermometer

What is a Thermocouple?

The Thermocouple is a thermoelectric temperature sensor which consists of two dissimilar metallic wires, e.g., one chromel and one constantan, coupled at the probe tip (measurement junction) and extended to the reference (known temperature) junction.

The temperature difference between the probe tip and the reference junction is detected by measuring the change in voltage (electromotive force, EMF) at the reference junction.

The absolute temperature reading can then be obtained by combining the information of the known reference temperature and the difference of temperature between probe tip and the reference.

How does a thermocouple thermometer work?



If two junction are at different temperatures (e.g. one junction is placed in a hotter region than the other), a small voltage is produced. The greater the difference in temperature, the greater the voltage produced across the ends of the two junctions.If one junction is kept at a fixed temperature such as 0*C, then the other junction can be used as a tiny probe to measure the other temperature.

e.m.f produced is inversely proportional to the temperature difference between reference junction and the probe.

Advantages

- ability to measure a large temperature range
- very useful in a variety of circumstances in many different industries
- respond rapidly to changes in temperature and can be used at high temperatures at which other sensors would be destroyed.
- very versatile,robust,fairly accurate
- small mass
- made rugged, simply constructed and are immune to shock and vibration
- can be made very small, fitting into applications that other temperature sensors
- measure the temperature, as well as be coupled with certain circuits in order to discontinue the heating process once the wanted temperature is achieved.

(This can play an important part in safety measures, thus thermocouples can be considered important safety )