Group, I worked for Rosemount, a manufacturer of precision resistance thermometers, for many years. Platinum does have a well-known formula for temperature versus resistance, with second order corrections.
But a sensor is not enough. You need to convert its physical property to a signal that is useful. This is done by some sort of temperature transmitter or conversion device. The device and the RTD are a system. The temperature system is calibrated as you would any other such system, by comparing it to a standard that is 10 times more accurate. So the question is, how accurate do you want it to be, just as it is for time and frequency standards. Boiling water with an ambient pressure correction is fine for some systems. More accuracy requires more purified water and a better pressure measurement. Similarly, the triple point of ice, water, and vapor depends on purity and knowledge of ambient conditions, as well as the heating effect of the stirrer. And that only gives you two points, with no knowledge of nonlinearity in between or outside them. There is plenty of literature on the subject, but it is not in the scope of precision time and frequency measurement. It is, however, summertime. Bill Hawkins _______________________________________________ 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.
