More About The Type J Thermocouple

By Hannah Sargent


An instrument that can be used for temperatures measurements is type J thermocouple. It has been used since 1822s, when an Estonian discovered that the junction between two metals create a voltage which is a function of temperature. This instrument is made from an alloy. The alloy is made from iron and constantan.

Considering that the constantan is made out of nickel and copper, the constantan has lots of properties. First of all, it is a great conductor of heat and electricity. This instrument is often used for temperatures measurements, control and to change a temperature gradient into electricity. It also is used in many industrial applications, but, mostly in the plastic industry.

As others instruments, it has a limited range, from minus 40 to 750 Celsius degrees. These instruments are very popular because of the way they employ a wide range of measuring standards as well as the quality voltage they are able to output. The superior voltage output leads them to a resolution of a higher temperature. They are composed from two wires, called legs. The first leg is manufactured from iron, and the second one from constantan. The one made out of iron is positive and the one made out of constantan is negative.

It is usable from 0 to 816 Celsius degrees, but it often is recommended to not use it above 750 Celsius degrees. Because they are not expensive, they are being used in multiple applications as: mass spectrometers, gas chromatographs, in the laboratory and for industrial equipment. These instruments are more used into the plastic industry. The way they are indicating the temperature is simple: they provide a very small voltage signal.

If its protected by a compacted mineral insulation, the instrument can be used from 0 to 816 Celsius degrees. The temperature range is 538 Celsius degrees. Even if it usually is usable until 816 Celsius degrees, it still is not recommended to use it above 750 Celsius degrees, because an abrupt magnetic transformation will cause permanent calibration. It also is highly recommended to use these instruments in inert, oxidizing, vacuum and reducing atmospheres up to 750 Celsius degrees.

These instruments are mostly used in science, mostly in the electrical engineering, and in industry. It can resist at higher temperatures if is protected by a compacted mineral insulation. But you must avoid use it in a sulfurous atmosphere above 540 Celsius degrees.

There are two stiles: bare wire and ceramic insulated. For a longer life its recommended to use a tube that will protect it. Since the wire made from iron will oxidize rapidly at temperatures over 540 Celsius degrees. These instruments are widely used in all kinds of industries. Their wide range of measurements makes them extremely popular. All these instruments, used in various applications are easy to obtain.

Type J thermocouple has been less popular than other types. The main application is with old equipment that cannot accept the modern instruments. This instrument, although it may not be very useful, can still be used in various application. It is cheap, and can offer a good accuracy of the measurement. It has precision. It actually is easy to achieve and the low cost make it very convenient. These instruments are popular temperature sensors. The instruments can measure a wide range of temperatures. They posses predictable output voltages and large temperatures gradients.




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