[volt-nuts] volt-nuts Digest, Vol 12, Issue 11

Dick Moore richiem at hughes.net
Wed Aug 25 19:26:37 UTC 2010

Hi, Marv -- RE my 3458 -- It was very clean externally, leading me to think it had been used in a test or lab environment, but it needed a display board and a ROM board, both of which I installed. Then it went to Loveland for calibration. That was last September. Because the ROM board was replaced, there was no "before" data to compare the cal to. It goes back to Loveland this September, and now there will be "before" and "after" data which will provide an estimate of drift in parameters. It is not an -02 high-stability option unit.

The ROM board change essentially made this a good-as-new unit, at least according to Loveland -- it passed all pre-cal tests with flying colors and cal'ed without problems.

I believe that Loveland uses a Fluke 572x calibration system, which for DC is at least as good as the 732B. As to AC -- well I think it probably is as good as there is right now for cal use outside of labs. The specs for the 3458 reflect the uncertainty of the calibration standards, and the AC specs definitely show that. I bought that 3458 for $1600 on fleabay -- didn't want to pay too much more because of the ROM battery problems on older units with the Dallas ROMs that had built-in battery back up. The new ROM board has ROMs that have a snap-on battery which is apparently easy to replace, though I wonder how long they will be available via Agilent....

In any case, the display board was $400+, the ROM board was $500+ and the cal was about $500, so my total investment to this point is around $3100 -- a lot, but worth it. I just trust the 3458 without wondering if it is right. It is the only high-res measurer in the shop now, so it is right by definition. As Steve Rooke likes to say, "A man with one clock knows what time it is. A man with two clocks isn't ever sure."

Dick Moore

On Aug 25, 2010, at 5:00 AM, volt-nuts-request at febo.com wrote:

> Message: 1
> Date: Tue, 24 Aug 2010 19:52:37 -0400
> From: "Marvin E. Gozum" <marvin.gozum at jefferson.edu>
> Subject: Re: [volt-nuts] Back to voltage
> To: Discussion of precise voltage measurement <volt-nuts at febo.com>,
> 	volt-nuts at febo.com
> Message-ID: < at jefferson.edu>
> Content-Type: text/plain; charset="us-ascii"; format=flowed
> Hello Dick,
> Thanks for your input.  Your posts on time-nuts have been invaluable 
> as was the thread here and all its contributors:
> http://www.mail-archive.com/time-nuts@febo.com/msg16497.html
> The last I read on time and volt nuts, your HP 3458a had it share of 
> trouble, but you describe here its working true now, did it take much 
> to get back into factory shape?

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