[volt-nuts] HP 3457A

[Dr. David Kirkby]

On 11 August 2013 05:10, Orin Eman <orin.eman at gmail.com> wrote:
> Well, lets discuss the 3456A I got from goldenrubi, calibrated.  They send
> a calibration certificate which claims that their standards are traceable
> to NIST.  I have no reason to doubt that.  The list of standards used is
> reasonable for a 3456A.

I can't comment on goldenrubi's ability to calibrate a 3457A, but I'm
pretty sure he had a VNA cal kit on eBay which was calibrated. I was
suspicious, but I can't recall the exact details. I can't find the
auction, but I'm 99% sure it was goldenrubi.

I know Orin knows about VNAs, so he at least will understand this. But
even if you don't, it should be clear that you can't calibrate a
device properly using a device of the same specification.

Anyway, goldenrubi has two items on eBay now, both related to vector
network analyzer, neither of which have cal certificates, but I
doubted the accuracy of some comments on those auctions. So I deceided
to use the "ask seller a question" and query things. As I suspected,
he does not have a clue. It should be noted

1) One kit (85032B) has a part missing, which he is clear about.
2) The same kit shows some adapters (which I think are not the correct
models), but the adapters are present. The auction says they are not,
so I query that too.

These two things are not central to the problem.

I also strongly suspect two of these parts in the 85032B are not
original, as they have no HP markings on them at all. I have one of
these kits, and parts clearly have HP markings on them.

1) http://www.ebay.co.uk/itm/111114143954 is a "TESTED" HP 83032B
typep N calibration kit.
2) http://www.ebay.co.uk/itm/190780743417 is a "TESTED" 85053A 26.5
GHz 3.5mm verification kit.

Bear in mind, the manuals for both devices states the equipment to
verify the performance of the kits is not commericially available. Now
goldenrubi tells me he can't calibrate them, but his reasons are
totally wong. He seems to think that he could calibrate the kits if he
had other kits of the same model. This is totally wrong.

I know for a fact the open and short standards should be checked by
mechanical dimensions, not electrical measurements. I have got that
from someone at Agilent who is a specialist in this area. If you look
at papers on the calibration of these things, you will find things
like laser micrometers are used.

=== My 1st message to  goldenrubi ====
Dear goldenrubi,

I'm interested in this 85032B. Can you tell me how it was tested? Can
you provide a calibration certificate? The auction states it does not
come with the APC-7 to N adapters, but they are in the picture. Do you
intend removing them? If so,

I'm also interested in the 3.5 mm verification kit you have in another
auction. I'd like to know again how it was tested and whether it is
calibrated.

Dave

- drkirkby
==========================

He replies, saying he has the network anayzers these kits belong to,
so that is how he tests them!!!!!  He says to calibate them he would
need another calibrated kit of the same model. This is total rubbish
as you can buy the kits easy enough (excepting the 85032B is
obsolete), but the manuals make it clear the equipment to verify the
performance is not commerically available.

======== goldenrubi  1st reply to me ======
Dear drkirkby,

I do not have the HP - Agilent 85032-60009 Short in this kit. I have
everything else. We have the Network analyzers that these kits belong
too. That is how we test them out. We cannot calibrate them or provide
certificate because we do not have this HP 85032B full kit and we
would need another kit that was calibrated in order to do a one on one
calibration on my kit. You get everything that is in the picture. I
will not remove any item. The 3.5MM verification kit was tested by us.
we have the equipment to test these kits out. WE do not have the
calibration kit to re-cal my kits on a one on one calibration. so we
cannot cal them. NO standards to work with.

- goldenrubi
================

I seek clarification, to make sure I have understood him correct

====== My second message to goldenrubi ====
Dear goldenrubi,

OK, I understand the 85032-60009 Short is missing from the 85032B
calibration kit on auction 11114143954. If I understand you correctly,
you can't calibrate the 85032B since you don't have another 85032B -
is that correct? Why does your auction for the 85032B say the adapters
are missing, when there are adapters in the picture? What equipment do
you use to test the 85053A 26.5 GHz 3.5mm verification kit in auction
190780743417? Am I correct in saying you can't calibrate it since you
don't have another 85053A verification kit, but if you had another
85053A you could calibrate it. Let me know if I have understood you
correct. Dave

- drkirkby
===========

His reply confirms what I thought.

======= His second reply to me =======
Dear drkirkby,

The short is missing from the picture. There should be 2 shorts, there
is only on. Yes, we need a counter part or other kit that was
calibrated in order to calibrated the two I have. We do not have a
standard (another kit) to use. We use the test equipment we have to
test them out. You understand everything I told you.
GREG

- goldenrubi
================================

I don't believe it is possible for anyone to truely verify the
performance of either of these kits other then the manufactuer.  In
the case of the verification kit, if one sends it to Agilent they (or
more likely Maury Microwave who make them for Agilent), would measure
the devices and write the data on them to a floppy disk and USB stick
(formally a tape, but tape is no longer supported). I believe the
format of the data is not public.

I certainly would not trust him to calibrate anything VNA related.

There are things you can do on a VNA, along with connector gages to
check gross errors. You don't need a kit of the same unit. But you
will never truely be able to calibrate one of these expensive high
precison kits. I would suggest one could

1) Check if the mating surfaces of the connectors are in the right
place using connector gages.
2) Check the attenuation of the two attenuators in the verification
kits are nominally the right value.
3) Measure the offset delay of the shorts using a VNA calibrated with
a calibration kit. It would not have to be the same kit.
4) Measure the fringing capacitance of the opens on a VNA and ensure
it fits the polynomial in the manual reasonably well.
5) If you have a suitable combination of VNA, calibration kit and
verification kit, then if one calibatrates the VNA, and the
verification passes, one would have reasonalbe confidence the
calibration kit is not too bad.

Properly calibrating these sorts of devices is not easy, and is very
expensive to get done. It costs far more to get a VNA calibraiton kit
calibrated than it does to get a VNA calibrated.

I produce a low-cost 3 GHz cal kit myself,

http://www.vnacalibration.co.uk/sales/

so I know things can be done which give reasonable accuracy without
laser micrometers, but I would never claim to be able to get the
accuracy Agilent do and could certanly never calibrate an Agilent kit.

Dave