Wednesday, 26 September 2012

Type J Thermocouple As The Temperature Sensor

By Hannah Sargent


A thermocouple is made from different materials, mostly metal alloys. Their general use is for temperature measurements and control. Type J thermocouple does not have unlimited range as others models but a higher sensitivity. It has in his composition iron and constantan alloy. Iron has a curie point which leads to a dramatic change in the characteristics. That determines the upper temperature limit.

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.

This model can support high temperatures. It can be used from 0 to 816Celsius degrees. Turning into Fahrenheit degrees, it means from 32 to 1500 Fahrenheit degrees. They are popular because they have a superior voltage range, and that can actually lead to the production of higher temperatures. They also have a relatively wide range for measurements, which make these models more convenient.

Each leg has a different property. The one that is made up of iron is a magnetic one. Because of the iron presence, its color is white and is susceptible not only to rust but the oxidation in entirety, particularly at temperatures below 0. The second leg is manufactured from constantan has the red color, is negative and it has no magnetic property. Constantan is an alloy of nickel and copper.

It also is recommended to use these models in oxidizing, vacuum or inert atmospheres up to 750 Celsius degrees. If they are used above 750 Celsius degrees, a magnetic transformation will cause constant calibration. These instruments have been improved over the past few years, so they can offer now a better accuracy and precision of measurements.

They are very used in gas chromatographs, mass spectrometers. The instruments are used for laboratory and industrial equipment. A faster response time requires a smaller diameter of the wires. All the models are supplied with 12 inch leads. Two stiles exist: bare wire and ceramic insulated. As mentioned before, a model has two legs, one from iron and the second one from constantan. The first one is magnetic and it can easily be identified from its distinct the white color. The second one is non- magnetic and it has the red color.

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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