[volt-nuts] 3457A - should I preserve SRAM contents, or purposely corrupt them by removing power?

Dr. David Kirkby (Kirkby Microwave Ltd) drkirkby at kirkbymicrowave.co.uk
Sun Jan 31 05:54:10 EST 2016

On 25 January 2016 at 11:12, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkirkby at kirkbymicrowave.co.uk> wrote:

> As noted in another thread, I want to replace a battery in a 3457A that
> has not been replaced in at least 11 years. The instrument has not been
> calibrated in that time either. At the time it was purchased from a dealer,
> I was told it was within specification, but if I wanted it calibrated I
> would need to pay. I never did have it calibrated, so have no historical
> data about this. I've no idea when it was calibrated, and have no cal
> certificate, so have no idea of the errors at the time of calibration.
> I now want to change the battery, *and* send it to Keysight for
> calibration - I have a healthy skepticism of 3rd party labs, so would
> rather pay more and get the job done by Keysight.
> I'm wondering if I would be better purposely removing the battery, and
> putting a short across the SRAM so I ensure the contents are definitely
> lost. My logic is that
> 1) If I send it to Keysight and the cal data is corrupt, they will set the
> meter correct.
> 2) If sent to Keysight, with the cal data in tact, then if its within
> specification they will not adjust it. So if the limit on some parameter is
> 1%, and the error is 0.5%, then it will not be adjusted. But if the SRAM is
> corrupted, the error will be huge (if it will read at all), so it would
> force Keysight to adjust it to the correct value.

> At that point the error should be effectively zero

> Thoughts?

Someone sent me a private email, saying that if by purposely removed the
power from the SRAM  caused the 3457A to fail its self-tests, which is may
well do, then Keysight may consider the 3457A needs repair, and so offer a
fixed-price repair. Hence my "trick" to get this calibrated as accurately
as possible would have backfired, and I'd be out of pocket. In fact, on a
3457A, the fixed-price-repair would probably cost more than the instrument
is worth, as these are not worth a lot now.

Hence I would not do this before getting clarification from Keysight. It
might be possible to get them to set it right, even if within spec, but I
think their calibration routines are very automated, so its probably not so
easy to get a special calibration, whilst paying for their cheapest
calibration service.


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