[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]

On 19 April 2018 at 16:42, <acbern at gmx.de> wrote:

> -a calibration certificate without uncertainsties is totally useless. in
> is not even a calibration.
> -I have never understood why people are so keen on getting things
> calibrated at Keysight.
>

I must admit I do have some concerns, about this. There are 3 aspects to
the calibration

1) Calibrate the voltage of the internal source using a 3458A. I have no
concerns a 3458A is not more than capable of measuring the voltage.

2) Measure the resistors in the 16340A. What puzzles me here, is that when
I had another 4339B calibrated, the limits on measuring those resistors
were symmetrical about the nominal values of 1e6, 1e7, 1e8, 1e8, 1e10 and
1e11 ohms. I would have expected the limits to be asymmetrical, because
those resistors are probably not their nominal value.

The columns below, from left to right are

Device type (whether the DUT is floating, or grounded one side).
Resistor setting (ohms)
Votage (V)
Measurement time (Long or Short)
Test limits (+/- ohm)
Test results (ohm)

FLOAT 1E6 100 SHORT +/- 0.0086E6 -.0019E6
FLOAT 1E7 100 LONG +/- 0.0063E7 -.0016E7
FLOAT 1E8 100 LONG +/- 0.0073E8 -.0027E8
FLOAT 1E9 100 LONG +/- 0.0093E9 -.0032E9
FLOAT 1E10 100 LONG +/- 0.0273E10 +.0095E10
FLOAT 1E11 100 LONG +/- 0.0453E11 +.0080E11
FLOAT 1E11 100 SHORT +/- 0.0550E11 +.0086E11
FLOAT 1E11 10 LONG +/- 0.0546E11 +.0113E11
GROUND 1E7 100 LONG +/- 0.0065E7 -.0017E7
GROUND 1E11 10 LONG +/- 0.0573E11 +.0107E11

That strikes me that the assumption is the values are what their nominal
values are, but I wonder how accurate they are.

3) Apply known currents, again using the test box.

I've asked Keysight if they are certain that the meter can be put within
specification, and if not whether it might be sent outside the UK to be
calibrated.

To be honest, I don't really NEED the uncertainties, but the fact they
can't provide them does concern me a bit.

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