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.
Re: [volt-nuts] HP-3458A Zero Reading
Bill wrote - There is an application note from Fluke, I think, on using DVMs for null meters. Fluke_-_Using_a_DMM_to_balance_752A_Divider.pdf is the name if it. I think it came from the Fluke Calibration Website. It is available at http://www.ko4bb.com/manuals/download.php?file=Fluke/Fluke_-_Using_a_DMM_to_balance_752A_Divider.pdf John K1AE -Original Message- From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Bill Gold Sent: Monday, July 27, 2015 7:54 PM To: Discussion of precise voltage measurement Subject: Re: [volt-nuts] HP-3458A Zero Reading Randy: I sure hope you are not trying to use 26 ga. telephone wire for the zero shorting wire. The manual recommends either 14 ga. or 12 ga. solid copper wire, this is the kind you can get for basic electrical wiring in conduit in homes, at least in the US. Generically called TW in electrician's language. My 3458A reads about -0.20 uv before AutoCal and less than +0.20 uv after, with the short as described in the manual. 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. I have been using the 3458A for nulling my 752A and have had no problems with my homemade low thermal leads as I described them to you. Belden/Pomona components. I use 100PLC. There is an application note from Fluke, I think, on using DVMs for null meters. Fluke_-_Using_a_DMM_to_balance_752A_Divider.pdf is the name if it. I think it came from the Fluke Calibration Website. Bill - Original Message - From: Randy Evans randyevans2...@gmail.com To: volt-nuts@febo.com Sent: Sunday, July 26, 2015 6:19 PM Subject: [volt-nuts] HP-3458A Zero Reading I shorted the input terminals of my HP-3458A with a short lead of copper wire, Bell telephone wire as recommended in the manual. The reading I get is around 000.00070 mV, or 0.7 uV with NLPC set to 100. I was trying to evaluate it's use as a null meter for my Fluke 752A divider. This seems a little higher than I would expect but no amount of running AUTOCAL or ZERO changes this amount. Is this considered acceptable? Randy AE6YG ___ 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. --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ___ 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
You talked about after an hour of warm up... I never turn mine off unless I have to... Like to move it, ship it or power outage. That said do not do anything like this until it has been on for 4 hours Then run auto cal Do not take any reading for 5 minutes after you change wiring or switches. Consider 1000 plc and or stats mode. Hope that helps On Sun, Jul 26, 2015 at 7:15 PM, Randy Evans randyevans2...@gmail.com wrote: A bit of a false lead. I took the readings after an hour of warmup. However, after about two hours, the zero reading went to less thatn 0.2 uV, which seems just fine to me. I guess i just needed to get a really good warmup time. However, the 752 readings are varying over several uV when doing the CAL procedure. I am currently using unshielded leads so I suspect I am getting a lot of noise. Time to invest in some really good cables I guess. I was hoping to build my own cables as Bill Gold had suggested in a previous thread. Randy AE6YG ___ 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] HP-3458A Zero Reading
In message canwu9jzp8mb-pfs8qr7kfobyjlgoeuc_0tqjbsvfw1xrnzc...@mail.gmail.com , Randy Evans writes: A bit of a false lead. I took the readings after an hour of warmup. However, after about two hours, the zero reading went to less thatn 0.2 uV, which seems just fine to me. I guess i just needed to get a really good warmup time. You may want to try to shade the terminals from air-movement when you work in that range, thermal sensitivity is not negligble. I had better luck using relatively thick (1.5mm^2) copper wire. -- 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.
