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Can anybody suggest a good thermistor for -40C to 20C range? This is for monitoring a refrigeration system. This range includes a lower limit than what most thermistors are rated for. Misc. info: will be measuring with 10 micro amp constant current device.

Eric Ratliff
www.icpdas-usa.com

We are satisfied using a 2252 thermistor. We use ours in a standard control range between -50C and +35C. The probes we use have a NTC. The electronics works in 5VDC logic. We have developed our own temperature module which has a wheatstone bridge and some noise filtering. Our resolution averages 51 counts per degree C change in the range of -50C to +20C. In the range of -20C to -50C is falls off to about 46 counts per degree C change.

We engineered the module ourselves in house and have been using them for almost 20 years. There is lots of helps for making the thermistor wheatstone on the internet. But I will say they are a hair puller to get right. Expect a good part of a week from start to finish. To read the values into the real world you just use some interpolation in your programming. Using all this we come in with an accuracy of +/-0.1C when above 0 and +/-0.2C when below zero.

Hope this helps,
John
Techni-Systems