RESISTANCE TEMPERATURE DETECTORS – RTDs

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.

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.

To get the maximum life from your Resistance Temperature Detector it is recommended that you use a protective well and terminal head. The well serves to protect the RTD from damage by the gas or liquid being measured. Protecting wells are available in stainless steel, carbon steel, Inconel, or cast iron, and they are used for temperatures up to 1100°C. To eliminate errors in taking measurements it is necessary to compensate for the length of leadwire used to connect the RTD to the readout. The calculations to correct this are relatively simple, and there are also 3-wire and 4-wire designs which help to minimize such errors. An example of a typical 3-wire measuring circuit is shown in the RTD Specifications Section.

Features of ARiDET Mineral Insulated Resistance Temperature Detectors
◦Time Constant of 2.2 sec or less
◦Temperature Range: -200 to +600 °C
◦Pressure Range: Vacuum to +50,000 PSIa
◦Shock Resistance to 1000G in all 3 axis
◦Withstand Vibration of ±50G, 60 to 2000HZ
◦Accuracy:±1 ohm @ 0 °C (±0.1% for 100 ohm)
◦Reproductibility: ±0.1% of resistance for 100 ohm element
◦Very Long Lengths. Entire length can be exposed to high temperature
◦Available with 4-20ma temperature transmitter/amplifier
◦Superior corrosion resistance with low carbon 316 ST/ST sheaths
◦Can be sharply bent with no change in performance
◦Full Technical Specifications

LABRATORY ACCURACY WITH INDUSTRIAL RUGGEDNESS
Platinum resistance temperature detectors are used for interpolation between the IPTS-68 fixed temperature points of ice and antimony (0°C to 630.74°C), generally used where accuracy and stability are most important. The ARiDET® approach to RTD’s will bring ±.05° laboratory accuracy to the toughest industrial processes – without special handling considerations. ARi Industries Inc. has combined the inherent accuracy of a precisely wound Platinum resistance element with AeroPak® compacted ceramic insulated cable. The result is a low cost yet rugged sensor that will take factory handling – retaining the stability needed for today’s precise process control.

Available with either the 99.999%+ high purity JIS C-1604-81 or 99.99% DIN 43760 temperature vs. resistance curve.

See the temperature vs. resistance tables in the RTD charts section for how to obtain laboratory accuracy.
For a more detailed explanation of how resistance temperature detectors work please visit our technical specifications page.