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.

Processing and manufacturing procedures are sensitive to heat. The speed of response is also important for any instrument used to monitor heat. This calls for careful study before selecting the metal to use. The signal to be sent to control towers allows effective monitoring to prevent compromise on the outcome.

The industries that benefit from this technology include manufacturers of appliances, automotive industry, control sections and HVAC. Production plants with measuring and testing units need to constantly monitor the temperatures. A higher level of consistency and accuracy is required to achieve desired results. Common metals for this purpose include copper, nickel and platinum.

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.

There are limitations to the use of these devices. They arise out of their behavior when exposed to heat in different circumstances. RTDs are not used where the heat levels go beyond 660 degrees Celsius. Platinum is easily and readily contaminated by impurities at such conditions. These impurities come from the sheath of such thermometers.

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.

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.

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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