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vendredi 16 mai 2014

How Resistance Temperature Device Works

By Tracie Knight


Temperature is measured using different methods depending on the environment. RTD or Resistance temperature device is based on the scientific fact that changing the temperature of a conductor will affect its resistance. The flow of electric current as a result of heating or cooling is used in calibrating the devices. The principle of correlation is used with a great deal of standardization.

Platinum is a common metal because it displays a constant reaction over a wider range of change in heat. This gives an incredible accuracy level which is important for industrial processes. Temperature sensitivity is likely to affect the results of a production process.

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 range of heat is important in determining the element to be used. Different industrial processes depend on the ranges to determine the products being extracted. It means that the element in use must not be distorted by high temperatures or be made to malfunction through freezing.

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.

RTDs face the challenge of maintaining accuracy when making conversions for the purpose of calibration. There is a delicate relationship between temperature and resistance in conductors. The interference of other properties affects the outcome which could lead to erroneous results and compromise industrial processes.

Extended exposure to heat alters the properties of some metals. This increases the possibility of giving a different reading at the repetition of a thermal cycle. These changes are captured in the definition of hysteresis. It has become a threat to the use of RTDs in areas where long running exposure and more sensitivity is required.

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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