Thermocouples

Thermocouples have been around for a long time and they can be found in both industrial and residential applications and devices. In electronics, thermocouples are used as a type of temperature sensor, but they can also be used as a means to convert thermal potential difference into electric potential difference.

Just a few of the many benefits that thermocouples have are that they are inexpensive and interchangeable. They have standard connectors which make them somewhat universal in nature, and can they can measure a wide range of temperatures.

There is a drawback to thermocouples, however, and the main limitation is precision. It can very difficult if not impossible to be within errors of less than 1 °C. For this reason, thermocouples are most suitable for measuring over a large temperature range, up to 1800 K.

If a particular project or device needs precision regulation it is often better to forego the use of thermocouples and instead use thermistors and RTD's.

As mentioned above there are a variety of thermocouples available. These are suitable for different measuring applications in the industrial, scientific, food temperature, and medical research fields. Designers and engineers will usually base their selection on the temperature range and sensitivity needed.

Thermocouples with low sensitivities (B, R, and S types) have correspondingly lower resolutions. Other selection criteria include the inertness of the thermocouple material itself, and whether or not it is magnetic.

There are some interesting aspects to thermocouples that students can learn. One of the more interesting aspects is that thermocouples can be connected in series with one another in order to form what is called a thermopile. This is an application where all the hot junctions are exposed to the higher temperature and all the cold junctions to a lower temperature.

A second interesting aspect to thermocouples when laid out in series fashion is that the voltages of the individual thermocouple devices will add up, which allows for a larger voltage over the entire series.

As you might imagine, thermocouples can be found in many different applications and devices. Students of electronics are highly encouraged to learn more about them as heat is one of the most dangerous issues associated with electronics and thermocouples are often incorporated into devices to help offset that heat. They are also used to make connections between devices. All in all, you will find thermocouples in many different places and understanding them will only be an asset to your skill level.