Are you reading this in-circuit and operating? The current flowing through the resistor will skew the reading.
Stupid question I know but had to be asked... DaveH > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Mitch Van Ochten > Sent: Thursday, June 28, 2012 18:43 > To: Discussion of precise voltage measurement > Subject: Re: [volt-nuts] Thermistor value for 732A Reference > 10V Standard > > Hi Tom, > > According to the Fluke 732A manual page 2-6 the nominal value > is between > 3k - 4k with the oven at normal operating temperature. Mine > checks 3.545 k > and has been within a few ohms of that reading each year for > five years. You > may have a heater problem. There is a protective thermal > fuse which can go > open, in series with the heating elements. It's purpose is > to prevent a > runaway oven from cooking everything. Once it opens you will > never get any > heating until it is replaced. > > > Regards, > > mitch > > > > ----- Original Message ----- > From: <[email protected]> > To: <[email protected]> > Sent: Thursday, June 28, 2012 7:04 PM > Subject: [volt-nuts] Thermistor value for 732A Reference 10V Standard > > > > > > > > Hi! > > > > Can anyone give me a rough value of the thermistor > resistance that is > > brought out to the front panel of a Fluke 732A DC Reference > Standard > > (lower > > left-hand side)? The thermistor is for the user to monitor the > > temperature of > > the oven that contains the voltage reference. I see a > resistance that > > starts out at 6600 Ohms (unit was nearly cold) and climbs > and levels out > > at > > about 8400 Ohms after a day, or so. Is this reasonable? > The thermistor > > is > > given in the parts list as RT2, a Fenwal JA41J1 (no longer > made) and on > > the > > schematic as a 10K @ 25C unit. So this doesn't make sense. > > > > Does anyone have any experience with this? Or is just > simpler to replace > > the thermistor with a 100 Ohm RTD and be done with it? Or > would this > > drive > > the calibration labs nuts? > > > > Any references or advice would be appreciated. > > > > Tom Leedy > > Clarksburg, MD > > _______________________________________________ > > volt-nuts mailing list -- [email protected] > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > > and follow the instructions there. > > > _______________________________________________ > volt-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
