Joe, your 335 is better than my 332D was -- zero stability was the most annoying, since there really wasn't any stability, although AC noise wasn't a big problem -- as Greg points out, using longish integration times on the meter really helps with that. I tried a variety of solutions, and while I got some improvement, I didn't get what I wanted. Then I picked up a 5440B, and that basically solved my issues with stability. A battery has low AC noise -- just basically the Johnson noise of its source resistance, which for a D cell is pretty low. As you note, with batteries (or Weston/Eppley cells) it's the DC drift, including temperature sensitivity, that gets you. At first blush, I like Warren's little zener circuit overall as a very simple and effective way to get low-noise, low-drift DC of a known value -- add a chopper amp like an LT1150 and a couple of wire-wound low-TC resistors and that's a great 10V source. Dick On Sep 26, 2011, at 9:12 PM, volt-nuts-request@febo.com wrote: > > Message: 1 > Date: Mon, 26 Sep 2011 20:28:01 -0500 > From: "J. L. Trantham" <jltran@att.net> > To: <volt-nuts@febo.com> > Subject: [volt-nuts] Fluke 335A > Message-ID: <4A67B9817BED40B384D8663D32E4D971@cardiac5f772ce> > Content-Type: text/plain; charset="us-ascii" > > My 335A is, seemingly, behaving but I have noticed two issues. > > > > First, there is a slow fluctuation in the 'zero' reading and requires > adjustment every day or so to make it read 0.00000+/-. > > Second, once adjusted, when set to 0.123456 volts, it fluctuates 2 or 3 uV > when monitored on an HP 3478A. > > Are these behaviors normal? If not, what suggestions are there to resolve > this? > > Thanks in advance. > > Joe