[volt-nuts] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?

[Dr. David Kirkby]

I have an HP 4339B high resistance meter. It can read up to 1.6 x 10^16
ohms, with a basic uncertainty of 0.6%. It has a built in voltage source of
up to 1 kV.

I've contacted Keysight (UK) and asked for calibration cost, with
uncertainties, for this 4339B. However, they have said they can't provide a
calibration with uncertainties, and when I asked why, they have said they
do not have an uncertainty budget available that suites that model. Looking
at the Keysight website, a calibration with uncertainties is available in
the USA, but I guess for whatever reason Keysight UK don't have this
ability on this specific instrument. On other instruments I have sent them,
I have never had this issue.

I expect if I really wanted to, I could get it shipped to the USA and
calibrated there, but I can't justify the costs that would be incurred if
it was shipped to the USA and back.

>From a practical perspective, I don't really need the uncertainties - it
was more for interest sake. I also have a reasonable degree of confidence
that as a reputable company, Keysight would not calibrate an instrument
unless they were confident they could determine if it is in or out of
specification.

The 4339B is a pretty obscure unit, requiring resistors up to 10^11 ohms to
calibrate it.

I'm sending this to Keysight with a blank EEPROM, so there will be no
calibration data whatsoever in the instrument. Hopefully that means
everything will be set right, and so likely to stay in specification longer
than it might otherwise do so. There are no trimmers in the 4339B - all
calibration is via the EEPROM. A 3458A is used for calibration of the
voltage source. I'm confidence the voltages will be measured accurately
enough, but a bit less confident about the values of the resistors used for
calibration.

Dave

Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892
http://www.kirkbymicrowave.co.uk/
Tel 01621-680100 / +44 1621-680100