[volt-nuts] Fluke 335A

[Dick Moore]

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 at febo.com wrote:

> 
> Message: 1
> Date: Mon, 26 Sep 2011 20:28:01 -0500
> From: "J. L. Trantham" <jltran at att.net>
> To: <volt-nuts at febo.com>
> Subject: [volt-nuts] Fluke 335A
> Message-ID: <4A67B9817BED40B384D8663D32E4D971 at 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