[volt-nuts] HP 3457A calibration?

[J. L. Trantham]

I've tried this on a 3458A and lost the data in the CALRAM due (I think) to
trying to read the data while the chip was still 'hot' from the removal
process.  Two other 3458A's were successful.

I've tried this on a 3478A (much more like the 3457A) and lost the data and
had to recalibrate the unit.  I have not sent it to Agilent for calibration
to see how 'successful' my 'home cal' was.

I know safe removal and replacement of the battery can be done and has been
done.  However, I really missed knowing the 'in tolerance' status of the
3458A.  I returned it to Agilent earlier this year and it was 'in tolerance'
from the calibration the previous year, so that is some consolation.  The
other two 3458A's, that underwent the 'successful' CALRAM replacement, were
both 'in tolerance' when returned to Agilent and again were earlier this
year, thus giving confidence that they are stable for a long term and likely
not needing 'calibration' on a yearly basis.

I recently sent two Fluke 289, 4 1/2 digit handheld, DMM's to Fluke for
calibration, one with a Calibration Date of 08/07/09 and Calibration Counter
of 1 and the other with a Calibration Date of 02/10/11 and Calibration
Counter of 1, and both returned with 'As Found - As Left' data and no
adjustments made (Fluke Z540 Cal).  This gives me great confidence in the
DMM's and their ability to be accurate for many years to come with little
need to return them to Fluke for 'cal'.  It would appear that they have been
'in tolerance' since their original calibrations some 2 to 4 years ago.

>From my perspective, as a 'neophyte volt-nut', knowing the 'in tolerance'
status of the DMM is very 'confidence building'.  That's all I'm trying to
say.

Again, good luck.

Joe 

-----Original Message-----
From: volt-nuts-bounces at febo.com [mailto:volt-nuts-bounces at febo.com] On
Behalf Of Joseph Gray
Sent: Tuesday, August 20, 2013 11:15 AM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] HP 3457A calibration?

I have replaced this type of battery in other equipment, so it isn't a big
deal for me. I'm sure I can do it without losing the cal data.

Joe Gray
W5JG
 On Aug 20, 2013 9:43 AM, "Dr. David Kirkby" <drkirkby at gmail.com> wrote:

> On 20 August 2013 14:51, J. L. Trantham <jltran at att.net> wrote:
> > If the battery is 'OK', I would favor just sending it to Agilent for 
> > calibration, unless you can 'SAFELY' change the battery while 
> > preserving
> the
> > cal data.
> >
> > Good luck.
> >
> > Joe
>
> If one accepts there is some risk changing the battery while 
> preserving the data, one has two choices.
>
> 1) Do as you say and leave the battery, preserving the cal data. This 
> however risk the battery leaking at some time.
> 2) Change the battery, losing the cal data, but virtually eliminating 
> the risk of leakage.
>
> To me at least, the path of least risk is the one to take.
>
> I suspect if one put a power supply in parallel with the battery with 
> a 10 k resistor in series, then the 10 k resistor would not drop 
> enough voltage to lose the ram data, but if it was accidently shorted 
> the current would be limited to a few hundred microamps. That's 
> unlikely to do any damage
>
> I guess for a volt nut, preserving the cal data is more important than 
> it is to me. Not damaging the meter is higher on my priority list.
>
> Dave
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