Interesting note. After the room cooled down from about 79F to 73F, and another ACAL, the meter now reads +000.00035 mVDC, a more reasonable value, although it does bounce around a couple of tenths of a uV.
Maybe that is OK? If so, then the only issue would seem to be the display has some faint pixels, which a new display should fix. Randy On Sat, Aug 16, 2014 at 9:59 PM, Randy Evans <randyevans2...@gmail.com> wrote: > > The unit seems to be working so far except for one issue. After doing an > ACAL, and making sure the Auto Zero is ON, I short the input leads with a > copper wire shunt across the inputs and the reading is approximately > -000.0023 mVDC. That seems rather high. I would expect the unit to short > the input leads internally and force a zero reading during the ACAL. > Anyone have any comments on this reading? > > Thanks, > > Randy > > > On Sat, Aug 16, 2014 at 3:37 PM, Richard Moore <richiem5...@gmail.com> > wrote: > >> Hi Randy -- sounds like your unit is in cal, based on your measurements >> of DCV and precision 10k resistor. >> >> Using autocal all is recommended before doing precision measurements, and >> I do that if it's been more than a day or two since last use. The autocal >> uses the internal Vref and an internal 10K resistor to do cal on everything >> else, so that tells you what the basic cal procedure is. I just got my 3458 >> back from Loveland, and that's what they did for me -- warmed it up, then >> ran autocal, then measured everything against a Fluke 5700, aided by an HP >> 3325, and another 3458. >> >> It has been 5 years since I replaced the display board (no "exchange" >> deal was available then AFAIK, so I don't know what's changed) and also the >> NVRAM board, which was dead, with one with the Snap-cap RAM chips. I did >> those replacements, then sent it home for cal, which was complete, since >> all the RAM was new. Now after 5 years, the unit passed all incoming >> performance tests and was sent back to me without a cal process of any >> kind. This tells me that an old, well-aged Vref module is a good thing. The >> 10VDC test had changed by a bit under 5ppm, or roughly 1ppm/year. >> >> They have a cal deal -- use code 1.090 -- press them for it -- and that >> saved me 30% off the normal price. I think this deal lasts until >> mid-September, so my recent "cal" ended up at just under $400 including >> shipping. I'm not sure the deal is available on new or first-time cals; my >> unit was in their data bank. >> >> But this is a long way of saying I don't think you need to send it for >> cal -- just push Auto Cal and Enter and wait about 10 minutes and you >> should be good to go. >> _______________________________________________ >> 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.