The 3456a is ~20x less accurate than the 3458a in VAC. That's as good as it gets. Here's a comparison of all the top DVM as provided in the 1993 HP equipment catalog, 1993 was unique in that it covered many generations of DVM/DMM many of which were soon to be dropped from sale. Click or go to the link: http://www.imagebam.com/image/f4f16c350823319 The 3456a shines in DCV. A used 34401a typically sells for $300-700, a 3457a ~ $200-400, 3458a ~ $2,000-5000 but a 3456a is ~$70, it offers very good bang for buck in DCV. ----- Original Message ----- From: "Richard Moore" <richiem5683@gmail.com> To: volt-nuts@febo.com Sent: Thursday, September 11, 2014 7:30:26 PM Subject: [volt-nuts] HP 3456A AC cal I'm trying to get my head around the AC cal procedure for the HP 3456A -- there is no full-scale cal, just some extremely finicky tweaks for the bottom ends of three of the four ranges. I really don't understand how this is supposed to work, especially since it is very accurate on all DC ranges (up to 500V -- above that some heating of the divider R seems to occur and it loses accuracy as the voltage increases). But on AC, the tweaks don't result in anything like an accurate level reading compare to my 3458A -- at 10VAC it is off by hundreds of ppm. Anybody shed any light on this? Is there a way to get full scale cal points in AC mode? Any mods to fix this -- lovely meter otherwise; I much prefer it to the 34401A I used to have, except for the overall bigness.... _______________________________________________ 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.