Friday, May 2, 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.

Platinum tops the list of metals used as conductors. It is favored by its consistency despite a wide range of change in temperature. This enhances its accuracy and reliability as a conductor to be used in monitoring temperatures during industrial processes. Its sensitivity to changing levels of heat gives it an edge over other conductors.

Heat is a vital element in processing and extraction of industrial products. Sensitivity to heat changes and response speed are important in achieving desired results. The metals must be studied carefully alongside the environment where the RTDs will be used. Sending the right information or signal to the control tower ensures that accurate steps are taken. This will prevent compromise on the processes.

Some of the areas where this technology is required include in the automotive industry, appliances, HVAC and control units. It also works in the test and measuring units of production plants. Instruments used in testing and measurement require similar levels of accuracy and consistency. This is what elements such as platinum, nickel and copper provide.

The best element for use as a conductor must display consistency over a wide temperature range. Sensitivity to slight increment or reduction in the amount of heat is also important. The sensitivity of such processes as extraction means that the highest possible accuracy degree must be achieved. This prevents scenarios where the outcomes are compromised.

Exposure to heat causes varying reactions which is considered a limitation when using RTDs. Temperatures beyond 660 degrees Celsius have been known to damage the conductor or cause it to misbehave. Too much heat causes impurities to contaminate the conductor. They come from the sheath and affect measurement given.

Boundary impurities and temperatures affect the resistance of RTDs when the temperatures are below 270 degrees Celsius or 3 Kelvin. This is attributed to the reduction in the number of phonons in the elements used. This is disastrous for any industrial process that requires sensitivity to heat. RTDs also have the challenge of small temperature changes.

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.

Exposing conductors to continuous heat is likely to alter their properties. This leads to inconsistencies during a thermal cycle. This is defined as hysteresis and threatens to push RTDs out of some operations. It also affects their sensitivity thus limiting their use. The conductors, however, respond well to lower temperatures.

The sheath also has the potential of conducting heat away from the process and thus affecting the outcome. Current being passed across the conductor may also come from other avenues. This is likely to affect the outcome. The number of wires used in the connection is likely to affect the results. Response time for the conductors is another challenge.




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