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Jeff,

The history of the 3457A on the way to you doesn't seem unreasonable. If
it was built in the early to mid 90's it may have been calibrated
annually until 97, and a year later when it was due calibration again it
may have been replaced by a more accurate DVM, or used for non-critical
measurements not requiring traceable calibration, or put on a shelf and
not touched for some time. Maybe the owner decided 2012 was a good time
to retire or reduce inventory or upgrade to a 3458A and the e-place was
the way chosen to sell off the unit coming to you.

Cheers,

Steve

On 12/31/2012 2:45 PM, Jeff Machesky wrote:

I didn't know that's how the revisions numbers worked. So the one I have
on the way is 1991 revision. Interesting.

I do fully plan on sending the meter off to Agilent, assuming it doesn't
have any issues. I now am starting to question why a meter would be a
'91 revision and last calibrated in '97 and then sold on ebay in

2012. Hmmm.

As to the confidence check I figure even if I use some low temp co
resistors and trim them ever so slightly down to precision I might get
an hours worth of checks out of the design before it's off by any amount
I would care about. The nice part about the Hamon divider is it appears
to be about how well you match the resistors, not the absolute value.
You also appear to get an order of magnitude greater accuracy then your
original matching. I suspect I can get this pretty accurate. Perhaps a
couple uv very high impedance voltage follower to make it all more
stable. I'm testing the divider now with some resistors I've matched to
better then 0.01%. The temp-cos on them are horrible however. Good
enough for testing.

Thanks,

Jeff

On 12/31/2012 1:21 PM, Steve Krull wrote:

The battery looks like it is original, so it could theoretically be up
to 25 years old based on the oft-quoted adage that adding 60 to the
first two digits of the sn prefix gives the year of the revision the
unit was built to. It could be much newer if that revision was in
production for many years, as is more likely the case. 25 years seems a
long time for that generation of battery technology. It is quite
possible the battery was replaced as recently as 2004/2005, just before
I got the unit. If that's the case whoever replaced it did an excellent
job as it looks like it's never been touched.

Your confidence check sounds reasonable. It would be interesting to the
group to see how your results compare with the "as received" numbers if
you do decide to sent your unit to Agilent.

Steve K.

On 12/31/2012 11:44 AM, Jeff Machesky wrote:

Thanks for the information Steve. Hopefully mine will have the 3.6

volt

battery seeing as how it has the newer serial number prefix. How old
do you figure your battery is to still have that voltage ?

On another note I think I'll get a 3.000 volt reference from
voltagestandard.com and build up really carefully a 0.1x and 0.01x

Hamon

divider to check the 300mv and 30mv ranges. Just as confidence check
until I can get it in for calibration. I could in theory check the
30v and 300v ranges by using 0.1x and 0.01x against those voltages
adjusting until the division matches the 3.000v reference and then
checking the results. So for the lower voltages I would divide by 10
or 100 the precision reference and for anything above the reference I
would divide and adjust until it matches the reference and take the
remainder. Hope that all makes sense.

3.00v * 0.01 for 30mv
3.00v * 0.1 for 300mv
3.00v * 1 for 3.00v
adj 30v * 0.1 until equal to 3.00v
adj 300v * 0.01 until equal to 3.00v

Thanks,

Jeff

On 12/31/2012 10:20 AM, Steve Krull wrote:

Joe and all,

I just had a quick look inside my 3457A again. Mine has the 3.0 volt
lithium battery, SAFT LX-1634. Obsolete at Agilent, as is the newer
battery. Google was no help either. Mine measures 3.03 volts and

there's

no evidence of corrosion so that's good. I couldn't see a date

code on

it; probably on the underneath side. I've replaced batteries by
paralleling the existing connections with an appropriate power supply
and then unsoldering the old battery with an isolated-tip iron and
soldering in the new battery. I've also carefully soldered a new

battery

in parallel with the old and then clipped out the old one. No

problems

with lost data so far.

I'm not sure how the cal numbers increment. I'll have to

experiment with

that sometime. Right now I need to repair the 1349D display in my

8757A

so I can get on with a sweeper plug in project, so the

volt-nuttery is

on hold for awhile.

Happy New Year to all!

Steve

On 12/30/2012 5:34 PM, J. L. Trantham wrote:

Steve,

Thanks for the data. Mine is also 2703A prefix with REV?:6,0 and
CALNUM?:98. Not a multiple of 34. Would be interesting to see

what the

CALNUM increments by after an Agilent CAL.

I, too, need to look at the battery condition. I have not looked

at the

manual regarding replacing the battery. Has anyone done that without
losing
the CAL Constants?

Joe

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Subject: Re: [hp_agilent_equipment] 3457a on the way

It would be interesting to see if a newer rev is out there. My 3457A
is s.n.
prefix 2703, with rev 6,0 and option 0, CALNUM=34. I wonder if

that's a

default number for anything less than a full cal at Agilent? The

last

calibration was at least 6 years ago and performed by what was then

Boeing

Military Airplane Company's metrology lab. I need to open it up and

check

the battery condition.

Steve

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