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Vol. 72, Issue 10, October 2006, pp. 729-730




Thermocouples vs. RTDs and Thermistors (Letter to Editor)


Jerry Gaffney

GEC Instruments, 5530 N. W. 97th StreetGainesville, FL 32653, USA

Tel.: 352-373-7955, e-mail: jerry@gecinstruments.com




Received: 20 September 2006



I read an article in a link from Sensors Web Portal that thermocouples typically are less accurate and stable than RTDs and thermistors (Flow Research Study Finds Shift to Non-Contact Temperature Sensors by Jesse Yoder, Sensors & Transducers Magazine (e-Digest), Vol. 71, No.9, September 2006). End-users who wish to achieve greater accuracy and stability in their temperature measurements can either switch to a different type of contact sensor, such as an RTD or thermistor, or can go to a different technology altogether such as infrared or fiber optic. The above is attributed to The Market for Temperature Sensors in the Americas, 2nd Edition, researched and published by Flow Research.


I agree that many thermocouples are less accurate and less stable than RTD's or thermistors. But I just wanted to let you know that here at GEC Instruments we have developed thermocouple instrumentation that can measure to an accuracy and repeatability of 0.04C or better over moderate temperature ranges. See test data in the pdf file.


And we have tests that show that measurements with our thermocouple instruments drifted at the ice point by only 0.02C after two years of use between 0 and 50C.

And thermocouples have other advantages, including the capability of very small sensor size, fast response and the capability for point measurements. We are currently building a 56-channel type T thermocouple instrument for an application where a major Aerospace company will be measuring refrigerant temperatures with very high accuracy at multiple locations inside a thin wall heat exchanger. Neither thermistors, RTDs nor non-contact sensors were suitable for this application.



Jerry Gaffney, Chief Engineer



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