lundi 12 mai 2014

The Principle Of Resistance Temperature Device

By Tracie Knight


There are different ways of measuring temperature depending on the circumstances. Resistance temperature device or RTD operates on the principle that changes in temperature alters the resistance of a conductor. An electric current is passed through a piece of metal which is used to indicate the reading. It works through correlation with another element whose reaction is known and standardized.

The most common metal for this purpose is platinum. It is widely used because it displays consistency over a wide range. The level of accuracy is incredible which makes it reliable for industrial processes. It has an incredible sensitivity that makes it preferable over the others.

Industrial processes are very specific when dealing with heat. This raises the need for high sensitivity and faster response. The metals used in this case are carefully selected to ensure that their response time is minimized. It gives a signal to control and monitoring units to take action before the outcome is compromised.

Some of the sectors using this technology include automotive, HVAC, control sections and manufacturers of electronic appliances. It also is installed in testing and measuring units for production plants that need to monitor temperatures. The conductor used must be highly sensitive to achieve reliable levels of accuracy. Other metals used as conductors include nickel and copper.

The properties that make an element favorable for this purpose include the heat range and how it responds to fluctuations. Processes such as extraction are sensitive to changes in temperature. Any distortion due to heating or cooling is likely to damage such appliances and compromise their operations.

RTDs face the challenge of inconsistency when exposed to changing temperatures in a heating cycle. Conductors are damaged or have their properties altered at 660 degrees Celsius. They result in dangerous inconsistency. The conductors are easily contaminated by compounds generated because of heat. The impurities fall off from the sheath.

Conductors behave different when contaminated by impurities. The impurities alter temperature changes and the trend can be noted at 3 Kelvin or 270 degrees and below. This is attributed to the presence of few phonons. It makes the conductors less sensitive.

Accuracy of the readings given by RTDs is sometimes compromised during conversion. The correlation factors that intervene in the process make calibration a huge challenge. This is a property that is likely to affect the fidelity of industrial processes.

Prolonged thermal exposure is likely to affect the properties of conductors used. There is a possibility of recording different measurements over a cycle of heat and cold. This behavior is referred to as hysteresis. It has been observed in different elements and threatens the use of RTDs in sensitive and long running industrial processes.

Heat is likely to be lost through the sheath and because of impurities that come into contact with conductors. The presence of foreign current is likely to affect the accuracy of reading given. Use of multiple wires is likely to affect the outcome. Metallic conductors used respond very slowly to changes during heating which is not appropriated for some sensitive operations.




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