[sdiy] Anyone in the UK used RS Calibration Services?

[Neil Johnson]

Tom Bugs <admin at bugbrand.co.uk> wrote:
>   Yeah, areas like this are more of interest to me than speed/service.

Well a good place to start to get a feel for a cal house is their UKAS
schedule (for UK cal houses).  This shows what they can calibrate to
under the UKAS traceable calibration, although most cal places will
also do a cheaper non-UKAS-but-still-traceable service.  Unless you're
doing really critical stuff like aerospace or medical it is arguable
whether you need that degree of traceability.

> A few years back I bought a not-too-expensive-but-def.-not-cheap
> hand-held multimeter which had the option to go through calibration
> before being sent to me. I opted for that and so the meter came with a
> sheet of test results. The thing was, though I can't remember the
> details now, the specs/tolerances on the report didn't really seem very
> good! (ie. the tolerance of the actual test equipment)

Depending on the meter and where you bought it from it may or may not
have been a worthwhile exercise!

> So, what sort of specs were given (I should check the HP meter's specs too)

Ok, so in my case, the 3478A is a 5.5-digit bench DMM.  The pre-cal
before check was done with a photocopy of the performance page out of
the HP manual.  Good enough for a quick check to identify any obvious
problems.

On the actual calibration certificate itself, for each test on each
range is printed
- applied value
- indicated value
- lower limit
- upper limit

To give you an example, on the 3V range there are nine tests including
shorted input, a variety of voltages, and also at different digits
(5.5, 4.5, 3.5).  One example line:

applied: 1.000000 V
indicated: 0.99999 V
lower lim: 0.99992 V
upper lim: 1.00008 V
pass/fail: pass

And so on for DC volts, DC current, AC current (@ 5kHz), AC volts
(@20kHz, 50kHz, 100kHz, 50Hz), and 4-wire resistance.

The certificate also shows the lab conditions, test procedure details,
the calibration equipment used, and the results of a PAT test.

Hope that helps.

Cheers,
Neil
--
http://www.njohnson.co.uk