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What Is a Platinum Resistance Thermometer?

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  • Written By: Alexis W.
  • Edited By: Heather Bailey
  • Last Modified Date: 20 October 2014
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A platinum resistance thermometer, most commonly referred to as a PRT, is an electronic device used within a circuit. Its purpose is to evaluate the changes that may occur in the amount of electrical resistance a material may have in instances of extreme temperature. The use of platinum is quickly becoming the standard in resistive thermal devices because of its ability to remain accurate in sensing the temperature in industrial processes that take place at or under 1112 degrees Fahrenheit (600 degrees Celsius).

A platinum resistance thermometer has become one of the most commonly utilized RTDs in industrial applications. A platinum resistance thermometer has also become a standard in resistance thermometers because of its utilization of platinum. The platinum increases its repeatability throughout the circuits the thermometer is used in.

PRTs are available in several different forms. Each of these forms has its own benefits and drawbacks. Carbon resistors, for example, have been used as the standard for some time because of their reliability and availability, as well as their inexpensiveness. With new forms of circuitry becoming the industrial norm, however, carbon resistors may not always be a compatible resource.

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Film resistors are an alternative to carbon resistors. Film resistors offer a quick response time and are inexpensive due to the thin film of platinum that is used in conjunction with the substrate layer of the resistor. These two components expand and contract at different rates, however, which can cause inaccuracy and strain on the resistor.

Another reason that platinum is being used as the standard material in resistance thermometers is because of its natural tendency toward chemical inertness. Other materials don’t typically have a significant effect on a resistance thermometer when platinum is used as the resistant material. As such, a platinum resistance thermometer can be used in a wider array of industrial applications. Furthermore, due to the fact that a resistance thermometer relies on temperature variances to provide the different level of resistance needed in the circuit, the accuracy that platinum provides is an advantage.

The limitations that platinum resistance thermometers suffer are found in applications that reach common temperatures that exceed 1200 degrees Fahrenheit (650 degrees Celsius). These extreme temperatures create a possibility for chemical impurities within the platinum, rendering the resistance thermometer inaccurate. Also, when the industrial application that requires the use of a PRT reaches common temperatures of -463 degrees Fahrenheit (-275 degrees Celsius) or less, the chance for inaccuracies with platinum resistance thermometers increases substantially.

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