[volt-nuts] Fluke 5200A instability...
Before I spend a lot more time on it, does anyone have any experience with the Fluke 5200A's feedback loop oscillating when in the 100Hz band position? Mine started to oscillate at about a 1/2Hz rate a while back. It is two to three orders of magnitude better when in the 1KHz and higher band positions. I can tell it is oscillating because if I watch the 3 least significant digits on my 3456A voltmeter, in the AC position, they keep repeating over and over and over... sort of fits a 1-2-3-1-2-3... count. I have replaced the bad capacitors in the power supply, and on a few of the boards. I have checked the supplies for voltage and ripple, and AFAIK they are ok. I tested the 2uf mylar integrator cap that is employed while in the 100Hz band, and replaced more than a few carbon composition resistors that were between 20 and 50% out of tolerance with no apparent affect. The carbon composition resistors I replaced were used to digitally adjust the gain of the integrator, so seemed likely to have an effect on the stability criterion of the feedback loop.. The DC Reference voltage seems to be very stable, and can be selected up and down with the voltage selection switches. I have tested all of the tantalums for shorts, and found none. I am running out of ideas. TIA, -Chuck Harris ___ 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.
Re: [volt-nuts] 3458A Zero reading
Dick it is all in trying to get the last little bit of accuracy out of the meter. 1000 NPLC and or math stat would do better than messing with the leads... All this gets into the law of diminishing returns. 1 ohm test lead in series with a 10Meg input resistance that only come into play on the 2 upper ranges will induce an error of 0.1 ppm. On Tue, Jul 28, 2015 at 1:26 PM, Richard Moore wrote: > Randy — not sure why you feel the need for shielded wire for DC > measurements, especially if you turn the LP filter on, unless you live > under a transmitter. I use twisted pair 22 ga. solid copper bell wire for > voltage measurments with no difficulties, and the thermals reduce very > quickly. Silver plated copper would be even better I suppose. Heavy gauge > wire is only needed for current measurements, which I seldom do. > > Dick Moore > ___ > 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. > -- *John Phillips* ___ 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.
Re: [volt-nuts] 3458A Zero reading
Randy — not sure why you feel the need for shielded wire for DC measurements, especially if you turn the LP filter on, unless you live under a transmitter. I use twisted pair 22 ga. solid copper bell wire for voltage measurments with no difficulties, and the thermals reduce very quickly. Silver plated copper would be even better I suppose. Heavy gauge wire is only needed for current measurements, which I seldom do. Dick Moore ___ 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.
Re: [volt-nuts] HP-3458A Zero Reading
On 7/27/2015 10:26 PM, Mike S wrote: > On 7/27/2015 7:54 PM, Bill Gold wrote: >> You will observe that the HP/Agilent/Keysight manual for the 3458A >> does not give any "zero" stability specs, at least that I can find. > > On DC 100 mV range, the standard model is spec'd for 14+3 ppm of range @ > 2 years from calibration, not considering temperature. That's 1.7 uV, > from my reckoning. The OP's reading of 0.7 uV is well within that - it > even beats the 90 day spec. Doh. That 14+3 actually equates to ~=3 ppm ~= 0.3 uV (since reading is essentially zero), but there's also temperature, which contributes > 0.115 / C. ___ 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.
