Temperature Controls (Pty) Ltd.
PT100 Resistance Temperature Detectors
Resistance Temperature Detectors are an accurate alternative to Thermocouples when utilised at temperatures from –200~+500’C. These units are locally designed and manufactured to suit customer applications.
Resistance Temperature Detectors, also known as RTD's, are wire wound and thin film devices which incorporate pure metals or certain alloys that increase in resistance as temperature increases and, conversely, decrease in resistance as temperature decreases. RTDs are similar to thermocouples in that they convert changes in temperature to voltage signals by the measurement of resistance. As a RTD gets hotter the resistance measured on it's element becomes larger, as it cools the resistance becomes smaller.
The Platinum Element RTD
The most commonly used type of RTD element is Platinum, these models are often referred to as PRTs or PRT100s. Platinum elements are popular because they can be used over a wide range of temperatures and feature a quick response time. Platinum's coefficient of resistance is nearly linear, as such, by using a platinum element resolutions of ±0.1 °C or better are possible.
Other Elements
Other elements can be used in RTD's which are less costly, the most commonly used alternatives are Copper and Nickel. The advantage to this is that the RTD will cost less money to manufacture and have a lower replacement value, but the drawback is that these elements have more restriction on the ranges they can be used due to non-linearities in the resistance vs. voltage curve. Also, there are problems with wire oxidation problems which are known to occur when copper is used as the element.
Why choose an RTD?
The advantages of RTD's include: stable output for long period of time, ease of recalibration, and accurate readings over relatively narrow temperature spans. When compared to thermocouples their disadvantages are: higher sensitivity to vibration, smaller overall temperature range, and a greater initial cost. For more help in determining if an RTD is the correct choice for your application, please consult our knowledgeable sales staff.
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