Hi Thermistors are often spec’d in terms of a tolerance on a value at a calibration temperature and a tolerance on a value for “beta” that goes into the standard thermistor R/T calculation. Typical parts are calibrated at something like 25C and you might get 1 or 2% at that point if you spend enough money. With a normal tolerance on beta, that 1 or 2% becomes a small part of the tolerance by the time you get past 40C.
Can you get a large batch calibrated at a higher temperature? Sure you can. They already are expensive parts and when you put an adder on top of that … the finance guys math goes tilt. If you need a very accurate number, the old style approaches were to turn hunt the oven or to measure the value of the part in a “local standard temperature of 95C” oil bath. Pretty much nobody does an OCXO either of those ways anymore. It’s all automated and uses a couple of measurements to set the part to best measured temperature performance. At some point in the performance equation, you don’t do anything more than take a guess at oven temperature and things work “good enough” for that spec. Bob > On Feb 27, 2016, at 11:21 PM, Hal Murray <hmur...@megapathdsl.net> wrote: > > > rich...@karlquist.com said: >> If you replaced the thermistor with an exact replacement, then you shouldn't >> need to change the pot. ... > > How repeatable are thermistors? How close do you need/want to get the > temperature? > > > -- > These are my opinions. I hate spam. > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
