[volt-nuts] 3457A - should I preserve SRAM contents, or purposely, corrupt them by removing power?, (Dr. David Kirkby (Kirkby Microwave Ltd))

[Four Designs Company]

A question to ask Keysight, if the instrument arrives without cal 
constants, will they consider that a "repair", or a calibration? Very 
different prices. I suspect that Keysight, and any other cal lab that 
has MetCal, will hook it up to a multifunction calibrator, computer and 
let it run.

If you jumper another battery with current limiting across the existing 
during replacement to preserve the cal, you could then ask for before 
and after data from the cal lab. This is typically an extra cost item.

I work on DMM's frequently, if this were in my shop, I would first make 
sure that the instrument is stable, regardless of the absolute accuracy, 
and that the relays  have not become noisy. This can be checked by 
rapping them lightly with something like a screwdriver handle .
Also a good opportunity to check and replace any electrolytic caps that 
have poor ESR.

I was just working on a pair of Data Precision meters, and both had 
noisy, unstable relays. This is a frequent problem, even with the 
"sealed" relays such as found in the HP. I would also make sure that any 
Front/Rear input switching is noise free, as these are often unused for 
years, if ever, and can cause problems.

Bob

On 1/31/2016 9:00 AM, volt-nuts-request at febo.com wrote:
> Re: 3457A - should I preserve SRAM contents, or purposely
>        corrupt them by removing power?
>        (Dr. David Kirkby (Kirkby Microwave Ltd))