Does anyone know where I can find a temperature switch or a sensor I can tie into a stand-alone controller that will sense down to -250 deg F?

 

Pyromation lists 100 ohm Platinum RTD's (probably the most common industrial configuration) with limits of operation of -328 to 1112 degrees F (-200 to 600 C), and accuracies as good as 0.01%. I assume other brands are similar. Just make sure your instrument can read that low (or get a general purpose process controller that you can scale any way you want, and put a 4-20ma tranmitter between the RTD and the instrument, but probably not in the cold zone). Watlow and Automation Direct.com both offer controllers that will read an RTD to -328F.

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Steve Myres, PE
Automation Solutions
(480) 813-1145

 

What type of controller? What are you wanting to do with the signal? What process are you measuring? Is the controller recieving any other signals? What type of signal can the controller recieve, i.e. thermocouple, rtd, discrete,...etc. In short, yes there exist equipment you can use.