The output impedance of both the 1v outputs is ~1k ohm. I wonder if Randy could check the 3458a input impedance with a 10M ohm resistor and the 10v output of the 732a.
I was thinking that the 732a needed a minimum battery voltage to allow the in cal led to turn on with the short to the Lo terminal. I guess I could try it on one of mine that is waiting for repair. Todd Sent from my iPad > On Aug 23, 2014, at 6:42, "J. L. Trantham" <jlt...@att.net> wrote: > > Randy, > > The 'IN CAL' LED is turned on as Todd describes. It goes off if power to > the unit is lost and, thus, calibration is lost. It is not related to the > battery charge LED. > > As I understand it, the units are designed to powered on 24/7/365 and are > 'IN CAL' once they are powered up, stable (weeks, months?), and have been > calibrated by your reference lab. Once power is lost, meaning lost AC and > batteries depleted, the 'IN CAL' light goes out and outputs are thereafter > unreliable. > > Once you decide to get the 732A calibrated, you will need to find a way to > ship it to the reference lab and get it shipped back while continuously > powered, connecting an external battery pack to the connector on the back of > the battery pack. The internal battery pack is likely to last only a few > hours. > > There are at least two types of connectors for an external battery, two 5 > way binding posts and a Hypertronics connector which is a small black > connector about 'dime' sized. I can find the part number for the mating > connector if you need it. > > I think the +/- 1 uV drift with the 10 V output and the 3458A are within > specs for both the 732A and 3458A. > > Not sure what to think about the drift on the other readings unless there is > some sort of 'dirt' on the 1 V and 1.018 V binding posts and/or ground. > > Good luck. > > Joe > > > > -----Original Message----- > From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On > Behalf Of Todd Micallef > Sent: Saturday, August 23, 2014 4:13 AM > To: Discussion of precise voltage measurement > Subject: Re: [volt-nuts] 732A drift > > Randy, > > I looked at the 3458a input impedance, and it is difficult to get the meter > set to the FixedZ (10M) mode. However, the 100v range is 10M. It should > default to HiZ on reset. > > I forgot to mention to check the outputs and guard resistance to ground. One > of my 732a had some foam baffling under the cover that had dry rotted. There > was a lot of leakage to ground. > I can't remember if the foam was on the older or newer versions of the 732a. > > The cal light comes on with a short wire stuck in the hole and connected to > a LO output terminal. I don't know, but maybe the battery charge led has to > be off. > > Todd > > Sent from my iPad > >> On Aug 23, 2014, at 1:16, Randy Evans <randyevans2...@gmail.com> wrote: >> >> I hope someone can help with a strange anomaly on either my 3458A or >> the 732A. The 732A 10V output as measured on my 3458A seems >> relatively stable over time (it bounces around about +/-1 uV but is it the > 732 or the 3458?). >> However, the 1.000 VDC output drifts downward at a rate around 1-2 uV >> per second as soon as I plug the 3458A into the 732 output. If I >> remove the 3458A and connect it back up after a few 10s of seconds, >> the reading goes back to what it started at and then drifts downward >> again. The 1.018V output also drifts downward but at a much slower >> rate and not as much. Now the question is: is it the 732 or the >> 3458A? I tried to see it on my Agilent 34401A DMM but it really >> doesn't have the resolution, but I do seem to see it on the 1.000VDC >> output. If it is the 732A, what would cause it to drift downward like >> that? Since the 3458A has an input impedance of >>> 10Gohm on the 1 and 10 V ranges, I wouldn't think the 732 would even >>> see >> the difference of whether the 3458A is connected of not, but it >> clearly makes a difference as to how long its connected and how long >> it's been disconnected. >> >> Any one have any conjectures? >> >> Also, what will turn on the "In Cal" light? What does it mean if it >> doesn't come on? >> >> Thanks, >> >> Randy >> _______________________________________________ >> volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> and follow the instructions there. > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.