On 5 April 2018 at 15:44, John Green <[email protected]> wrote: > Why has no one mentioned thermocouples? > I had some experience with thermistors a few years back designing thermal > attenuators and equalizers for CATV. NTC thermistors can have a large > change of resistance for a unit change in temperature. They aren't linear, > but there are formulas for computing resistance vs temp. PTC thermistors > have a much smaller change per unit change in temp., but are much more > linear. And, they are susceptible to self heating, which makes things > interesting. If I remember correctly, in my research something called an > RTD was supposed to be the king when it came to accuracy and repeatability. > As someone else has stated, the IC devices are supposed to be quite good, > but you have to interface with them. >
Keysights nano volt / micro ohm meter takes https://www.keysight.com/en/pd-1000001296%3Aepsg%3Apro-pn-34420A/micro-ohm-meter?cc=ZA&lc=eng can do direct SPRT, RTD, Thermistor, and Thermocouple measurements SPRT = Standard Platinum Resistance Thermometer I don't claim to know much about this, but the uncertainty quoted for the SPRT probes with that meter is 0.003 deg C. When I Google SPRT probes, I see they are incredibly expensive - many thousands of USD each. I'm a bit puzzled there seem to be a number of 3-wire platinum resistance thermometers. I can understand using 4-wires for a Kelvin connection, but can't understand the use of 3-wires. Of course, for environmental monitor in a lab, one is most unlikely to need very high accuracy. Dave _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
