[time-nuts] Volt-nuts cooperation?

WB6BNQ wb6bnq at cox.net
Sat Jun 20 16:50:08 EDT 2009


Hi Dick,

I am a little confused as to your needs.  On the one hand you feel the hp3458A is
a fine instrument only needing “CAL” every 2 years, yet you then say it needed to
be “CAL’d” every 2 days to stay repeatable.  That does not sound very encouraging
and is indicative of other problems.

I would like to know why you feel this particular instrument is so crucial ?

Particularly as you have within your own means just about everything to verify
your own equipment beyond anything reasonably needed.  The only item missing from
your list is a damn good null meter; the Fluke 845.

You have the best there is in a voltage standard with the 732A, assuming they are
working correctly and verified (i.e., calibrated) by a highly reputable source
like Fluke.   Even without the null meter you could easily jump start your own
verification process to improve your confidence.

The only other “NICE” thing to have would be Fluke 720A Kelvin-Varley divider.
For $1000 you could easily obtain the 845 and 720A.  With the 720A you could
prove, without doubt, each and every digit in your 7 ½ digit meters, not to
mention the 5440B.

The race for digits is a fun “hobby” but a truly wasteful effort because the real
world does not operate in a finely tuned calibration lab with every nuance of the
environment controlled beyond reason.  Even if you had such a lab in the basement
(some do), playing around at even just 6 digits requires knowing how to account
for a number of not so easily proved variables in the measurement process.

Of course, if this is a commercial concern like trying to satisfy a government
contract, then all bets are off.  Such a game guarantees the race.

Bill....WB6BNQ
wb6bnq at cox.net


Dick Moore wrote:

> A couple of times a year, I could really use an HP 3458A. No way can I
> justify spending upwards of $4-5k for such limited use. So, maybe some
> of us could form a buyer/user group to share the cost of one of these
> instruments, which could put it in the range of affordability for
> each. For example, ten of us could have the instrument for two weeks
> each twice a year, and the cost for each comes down to that for a
> 34401A.
>
> These instruments ship well (at least within the continental US, via
> FedEx or UPS), are very stable, and self-calibrate, needing a full cal
> (which uses a 10kohm resistor and a 10VDC source) once every couple of
> years to keep within tolerable specs. I've rented one once and I found
> that it really needed to self-cal once every couple of days to stay
> repeatable, especially on ohms and AC.
>
> My confidence in my Fluke 5440B Direct Valtage Calibrator, two Fluke
> 732A 10V standards, and two Datron 1082 7-1/2-digit DMMs would go way
> up, not to mention keeping a few other things checked and accounted
> for, like resistance standards.
>
> I'm willing to ante-up up to $1k to get us started, if there is any
> interest here among the US time-nuts.
>
> Best to reply to me at:
> richiem at hughes.net.
>
> We can work our details if the interest is sufficient.
>
> Best,
> Dick Moore
>
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