On 11 August 2013 15:39, Robert Atkinson robert8rpi@yahoo.co.uk wrote:

I think it depens why you want the cal certificate.

1. If it to keep the BSI person happy to keep your ISO 9001
   acreditation, then I guess as long as it has a cal certificate that is
   ok, so use the cheapest dodgy cal lab.

2. If the purpose of the cal certificate is to get the highest price
   when selling something, then a cal certificate by some dodgy cal lab
   is probably all you need. 99% of buyers are not going to question who
   did the cal, and their ability to do it.

3. If you want to know the instrument works correctly, and have it
   adjusted for best performance, then it is a very different matter. One
   is probably better sending it to the manufacturer in many cases.

I want to know my VNA works properly, so that is going to Agilent this
week. The cal cost on my VNA is about 5% of what I paid for the VNA.
It would be much more difficult to justify sending my 3457A to
Agilent, when the cal cost will probably be more than what I paid for
the instrument.

How useful is this

http://www.ebay.com/itm/281149723636 ?

On the fact of it, the device would give one a reasonly high
confidence something is working readlably well. I wonder if that is
good enough for a 3457A.

As I wrote earlier, I think there is a very cosy relationship between
cal labs and test equipment dealers. It is in both their interests to
get cal certificates on items even if they are not 100%. A T+M dealer
is not likely to use a cal lab that keeps sending items back marked
"Out of specification" or similar. A cal lab does not want to lose a
customer.

Dave, G8WRB.

On Sun, Aug 11, 2013 at 2:55 PM, Dr. David Kirkby drkirkby@gmail.comwrote:

It would give a reasonable check for gross errors.  They do claim to be
using a 3458A to cal them and give the 3458A cal certificate number.

Personally, I use a Geller Labs SVR-T for voltage checks at 10V

http://www.gellerlabs.com/Voltage%20References.htm

Joe Geller's calibrations are NIST traceable through his Fluke 732B.  A new
Agilent 34461A reads the SVR-T at about -3ppm, though it's a moving target
due to the temp-co of the '61A.  The goldenrubi supplied 3456A reads the
SVR-T at 8ppm high - inside 24 hour specs, but uncertain given the SVR-T's
claimed transfer accuracy of 5ppm.

I also have a Geller SVR that has been back twice for calibration.  The
first time back it was found to have changed by 1ppm.  The second time
back, I specified a different temperature so there was no as received
data.  The SVR is a reasonable choice if your lab stays at a constant
temperature.

I should go get the kelvin clips out and compare the 3456A against the '61A
on some 10k precision wirewound resistors I have.

Orin.

I don think it would be useful for serius purposes.

2013/8/12 J. Forster jfor@quikus.com

--
Zbyszek

On Sun, Aug 11, 2013 at 3:36 PM, Orin Eman orin.eman@gmail.com wrote:

I did.  The resistors are MR102 series 0.01% 1/8W wirewound:

34461A: 10.000 82 +/- 0.000 90
3456A: 10.000 98 +/- 0.000 58

Using 90 day specs for the 61A and 90 day plus 0.0004% per month for the
56A.  Yes, the 3456A resistance specs are better than the shiny new 34461A.

I also compared the DC voltage ranges from 0.1 to 1000V and other than on
the 1KV range, results were within 10ppm.  Still, given the 3456A spec
sheet says add .12(input voltage/1000)^2 % on the 1KV range, I can't
complain; I got 999.984 on the 61A and 1000.062 on the 56A.  I'm pretty
sure that the superscript 2 in the spec meant squared, not that it matters
for 1000/1000.

Now has anyone calibrated a Fluke 343A?  The instructions in the manual are
entertaining.  They tell you to adjust the 1000V range to +/- 1mV, but the
post calibration check says that a freshly calibrated unit should be +/-
100uV at the 1000V setting.

Orin.

Hi ,
Newer does not mean better. It's not "nuts" level, but my Fluke 8060A 4.5 digit handhelds are more accurate and stable than my newer 89 IV. However most "engineers" would pick up the 89.
I agree with Dave on UK " engineers" For many years I've been a member of the very few groups of engineer in the UK who need a licence to do their job - aircraft, but even that has been diluted since EU regulations came into force. I'm also a Chartered Engineer similar to PE in the USA. As I understand it most US States require you to be a PE before you can do business as an "Engineer". In the UK it's a bloke with an oily rag and big hammer :-(
 
Robert CEng MRAeS G8RPI

From: Orin Eman orin.eman@gmail.com
To: Discussion of precise voltage measurement volt-nuts@febo.com
Sent: Tuesday, 13 August 2013, 5:56
Subject: Re: [volt-nuts] Calibration and Certification - Trust and detail

On Sun, Aug 11, 2013 at 3:36 PM, Orin Eman orin.eman@gmail.com wrote:

I did.  The resistors are MR102 series 0.01% 1/8W wirewound:

34461A: 10.000 82 +/- 0.000 90
3456A: 10.000 98 +/- 0.000 58

Using 90 day specs for the 61A and 90 day plus 0.0004% per month for the
56A.  Yes, the 3456A resistance specs are better than the shiny new 34461A.

I also compared the DC voltage ranges from 0.1 to 1000V and other than on
the 1KV range, results were within 10ppm.  Still, given the 3456A spec
sheet says add .12(input voltage/1000)^2 % on the 1KV range, I can't
complain; I got 999.984 on the 61A and 1000.062 on the 56A.  I'm pretty
sure that the superscript 2 in the spec meant squared, not that it matters
for 1000/1000.

Now has anyone calibrated a Fluke 343A?  The instructions in the manual are
entertaining.  They tell you to adjust the 1000V range to +/- 1mV, but the
post calibration check says that a freshly calibrated unit should be +/-
100uV at the 1000V setting.

Orin.

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On Mon, Aug 12, 2013 at 9:56 PM, Orin Eman orin.eman@gmail.com wrote:

Make that ".012*(input voltage/1000)^2 %"... Oops.

Orin.