Tuesday, May 13, 2014

How Resistance Temperature Device Works

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.

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 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.

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.

Impurities found at boundaries and changing temperatures have a significant effect on the behavior of conductors in RTDs. This has been clearly noted when it is below 270 degrees or 3 Kelvin. The elements used have very few phonons which explains their behavior. This affects their sensitivity to slight changes in temperature.

The challenges posed by the use of RTDs include accuracy when converting the readings. The relationship between resistance and temperature is a delicate one and easily affected by other conditions. Sensitivity changes depending on heat. This is likely to give erroneous results.

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.

Interference from the sheath and impurities on the device cause loss of heat. This affects the accuracy of such devices. There is a possibility of current flowing through the conductor from other sources. Other factors that affect accuracy include the number of wires used as conductors. The response time for these devices is not satisfactory in some instances.




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