[volt-nuts] HP 3457A

[Dr. David Kirkby]

On 11 August 2013 10:23, Charles Steinmetz <csteinmetz at yandex.com> wrote:
> Orin wrote:
>
>> They send a calibration certificate which claims that their standards are
>> traceable to NIST.  I have no reason to doubt that.
>
>
> Owning standards and instruments with traceable calibrations is necessary
> but not sufficient for making traceable calibrations with them.  For a
> calibration to be traceable, the lab that did the calibration must be
> accredited.  If the lab is accredited, the calibration certificate would
> certainly identify the accrediting body.
>
> Does the certificate you received identify an accrediting body?
>
> Best regards,
>
> Charles

Techmaster Electronics

http://www.techmastertest.com/techmaster/

is NIST tracable and acredited. I would not trust them to calibrate a
3.5 digit DVM! There are a number of things I have seen cal
certificates from them, which I don't believe they can calibrate.

My Agilent 85033E 9 GHz 3.5 mm cal kit for my HP 8720D vector network
analyzer (VNA) was calibrated by them. They used an obsolete 6 GHz N
calibration kit (85032B), some EM modelling software and an obsolete
VNA. Yes, I am not mistaken, a 6 GHz ***N*** cal kit to verify a 9 GHz
***3.5 mm*** cal kit. The 85033E manual states the equipment to verify
the performance of those cal kits is not commerically available. From
what I understand, the verification of performance would need
mechanical measurements, not just electrical ones. The cal certificate
has no mention of a connector gage, laser micrometer or similar being
used. In fact, the manuals for the high end cal kits which include
connector gages, say they are only to detect gross errors. They read
to 0.0001", but that is not enough to fully check the connectors in a
cal kit.

The cal certificate for my VNA states "option 010 added". That is a
software option that enables the time-domain functionality. I find it
very hard to believe that was added legally, given the option is
obsolete and can't be bought from Agilent any more. If a commerical
cal lab adds an option illegally, do I trust them? It could have been
a typo, but when I got the initial invoice for my VNA it only listed
the option 1D5 - no mention of the 010. I later got the dealer to
change it, so my invoice states it has both optons 1D5 and 010. The
sale was agreed with it stating it had option 010, so I wanted to see
it on the invoice. It's also interesting that the dealer I bought from
has a number of VNAs on eBay. Every one of the same series of VNAs has
option 010. But he has an 8510 and PNA analyzer too, but neither have
option 010. This could be conincidence, but it is known that the
series of VNAs I have can be hacked fairly easily. That is not so with
the 8510 or PNA series, both of which need encrypted keys.

I was in discussion with a US test equipment dealer, and he admitted
his company had discovered a number of dodgy cal labs, though he said
there was some very good ones. One he felt could do a 3458A better
than Agilent.

I think you need to have trust in a cal lab.  I would not trust a cal
lab unless I had specific information to confirm they were good. I
think there is quite a cosy relationship between calibration houses
and test and measurement dealers. It is in the interest of the cal lab
to give out certificates with not too many questions asked. Then the
dealers will go back to them. A dealer wil not want to use a cal lab
that gives him too many failures.

I know someone who is looking to buy a VNA off of a dealer, and
offered to pay extra for them to send it to Agilent for calibration,
rather than Techmaster. cal certificate it has The company declined
"in case it failed the Agilent calibration."

I suspect a DVM, especially one of 6.5 digits, is much easier to
calibrate than a VNA or VNA calibration kit. One could verify the
performance with nothing more than an 3458A, and a number of lesser
mutlimeters. But can the cal lab adjust it, if it is near the limits
of its specification?

I have a 3457A myself and if I send it out for calibration, I'd send
it to Agilent. I'm sure there are other commerical labs able to
calibrate such an old meter, but who can I trust?

If someone knows of a UK lab, that is really able to do a 3457A well,
I might consider sending mine to them if they were considerably
cheaper than Agilent. Unfortunately, on a 3457A, an Agilent cal will
cost as much as the meter is worth. On a 20 GHz VNA, the instrument is
worth far more than the cost of an Agilent calibration, so I have less
concerns about spending the money.

Are there any serious volt-nuts in the UK able to verify my 3457A is
within spec, and how far it is inside the spec? I'd rather send it to
a respectable volt nut, than an unknown calibration lab.

Dave