Re: [volt-nuts] 3458A Zero reading
In message 19942e77-f4fd-4ba5-82cd-75a35bb5a...@gmail.com, Richard Moore writ es: Heavy gauge wire is only needed for current measurements, which I seldom do. Heavy gauge wire has different thermal behaviour than think wire (area deepends on radius squared, surface only on radius) It is not always obvious which behaviour is preferable. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] 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 richiem5...@gmail.com 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 — My 3458A manual specs 12 or 14 gauge solid copper wire for the short, bunt in to a U shape. I use 14 gauge. Poul-Henning’s comments about thermals are well-taken — even a simple folded up carboard shield helps. But I think you’re near the limit. ___ 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
I use a 8 oz styrofoam cup to isolate air currents around the 3458A terminals when zeroing with shorting bar Sent from my 20 Texas sized iPhone On Jul 27, 2015, at 2:57 PM, Richard Moore richiem5...@gmail.com wrote: Randy — My 3458A manual specs 12 or 14 gauge solid copper wire for the short, bunt in to a U shape. I use 14 gauge. Poul-Henning’s comments about thermals are well-taken — even a simple folded up carboard shield helps. But I think you’re near the limit. ___ 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.
Re: [volt-nuts] 3458A Zero reading
I used a 12 AWG wire formed into a U shape for the short and the zero voltage measured less than 0.2 uV after a good 2+ hour warmup. However, I am seeing drifts of several uV for the 752 calibration. I was using TV twin lead to connect the 732 to 752 and 752 to 3458A since that's really all I have for now. I suspect thermals are killing me so I need to find some low thermal shielded differential cable to connect from the 752 to the 3458A. I did not see anything like that in Pomona's arsenal. I was thinking about Bill Gold's idea of making my own but I think it would end up being \very stiff. Any other ideas for a good source of shielded copper wire twinax? Randy AE6YG On Mon, Jul 27, 2015 at 4:10 PM, J M via volt-nuts volt-nuts@febo.com wrote: I use a 8 oz styrofoam cup to isolate air currents around the 3458A terminals when zeroing with shorting bar Sent from my 20 Texas sized iPhone On Jul 27, 2015, at 2:57 PM, Richard Moore richiem5...@gmail.com wrote: Randy — My 3458A manual specs 12 or 14 gauge solid copper wire for the short, bunt in to a U shape. I use 14 gauge. Poul-Henning’s comments about thermals are well-taken — even a simple folded up carboard shield helps. But I think you’re near the limit. ___ 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.
