Agilent calibration - certificate for a vector network analyzer (VNA)
Since there has been a few discussions about calibration, and in
particular Agilent calibration, I thought I'd share my calibration
certificate for my VNA which came back from Agilent (UK) last week.
It is much more informative than the certificate issued from a US
calibration laboratory
a year earlier for the same instrument.
Note the instrument was not adjusted. The instrument has an intermal
oscillator and also a high precision version which is an option. Both
were sligltly off, but neither was adjusted as they met the spec.
There some comments on this thread
http://www.home.agilent.com/owc_discussions/message.jspa?messageID=109805
from an Agilent VNA expert that
"I will be very sceptical when a VNA calibration service does not
include a cal kit and verification kit. "
The other lab did not use a verification kit and the calibration kit
they used was an Agilent "economy" model 85052D, which uses fixed
loads, not the more accurate sliding loads of the much more expensive
85052B calibration kit.
I personally don't grudge paying Agilent £500 (~$750) for the
calibration. In contrast, unless I just needed the cal certificate to
satisfy somebody else, I would not spend a penny getting it calibrated
by the other lab.
I think on something as complex as a VNA, one really is better letting
the manufacturer calibrate it. On a 6.5 digit or less multi-meter,
there are probably a lot of labs able to do a decent job. Personally
though, if I get my 3457A calibrated I will send it to Agilent, since
I don't personally know of any lab that is competent to do it. It is
less justifiable to me to spend a lot of money getting an inexpensive
instrument calibrated.
Dave
David,
That is quite a difference between the two certificates. The Techmaster one
doesn't tell you anything about what they actualy measured, or the
uncertainties. You have to trust that they know what they are doing and
that they actually did it. With the Agilent certificate, there is data to
give you confidence that things were done properly.
Thanks for posting those. It was educational.
Joe Gray
W5JG
On Sat, Aug 24, 2013 at 6:20 AM, Dr. David Kirkby drkirkby@gmail.comwrote:
Since there has been a few discussions about calibration, and in
particular Agilent calibration, I thought I'd share my calibration
certificate for my VNA which came back from Agilent (UK) last week.
It is much more informative than the certificate issued from a US
calibration laboratory
a year earlier for the same instrument.
Note the instrument was not adjusted. The instrument has an intermal
oscillator and also a high precision version which is an option. Both
were sligltly off, but neither was adjusted as they met the spec.
There some comments on this thread
http://www.home.agilent.com/owc_discussions/message.jspa?messageID=109805
from an Agilent VNA expert that
"I will be very sceptical when a VNA calibration service does not
include a cal kit and verification kit. "
The other lab did not use a verification kit and the calibration kit
they used was an Agilent "economy" model 85052D, which uses fixed
loads, not the more accurate sliding loads of the much more expensive
85052B calibration kit.
I personally don't grudge paying Agilent £500 (~$750) for the
calibration. In contrast, unless I just needed the cal certificate to
satisfy somebody else, I would not spend a penny getting it calibrated
by the other lab.
I think on something as complex as a VNA, one really is better letting
the manufacturer calibrate it. On a 6.5 digit or less multi-meter,
there are probably a lot of labs able to do a decent job. Personally
though, if I get my 3457A calibrated I will send it to Agilent, since
I don't personally know of any lab that is competent to do it. It is
less justifiable to me to spend a lot of money getting an inexpensive
instrument calibrated.
Dave
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On 24 August 2013 18:55, Joseph Gray jgray@zianet.com wrote:
David,
Hi Joseph
That is quite a difference between the two certificates. The Techmaster one
doesn't tell you anything about what they actualy measured, or the
uncertainties. You have to trust that they know what they are doing and
that they actually did it.
I think Techmaster certificates are useful to T+M dealers, as they can
sell things for a higher price. Their certaificates are also useful to
end users that just need a certificate to satisfy some institute or
body. But I don't believe it would satisfy a competent engineer who
really wanted to know if the instrument was working properly. A
competent enginner would not be too conviced.
When an Agilent VNA calibration expert (Ken Wong) wrote on the Agilent
VNA forum that "I will be very skeptical when a VNA calibration
service does not include a cal kit and verification kit." and that
Techmaster cal certificate did not use a verification kit, one has to
be sceptical.
The fact Techmaster also issued a cal certificate for a calibration
kit makes me suspicious too. Apparently you need access to primary
standards to verify they are in spec.
There is something else interesting on that Techmaster certificate.
Note it says "option 010 added". That is a software option (enables a
Inverse Fourier transform to convert frequency domain data to time
domain). It is no longer sold by Agilent. I do wonder if that was
legally added. Buying that option for a new VNA costs several thousand
dollars, but the 8720D was last made in around 1999, and has been
unsupported since 2004. I suspect these cal labs are useful for things
like getting software options added! Agilent will certainly not sell
the option.
With the Agilent certificate, there is data to
give you confidence that things were done properly.
Yes. Note the Agilent calibration is not acreditated by anyone. I
could have had an acredited calibration, but I did not want to pay the
extra 50% or so. From what I understand, the VNA would be calibrated
in exactly the same way. But it costs Agilent money to get acredited
for the calibration, so they pass that cost onto those that want it
acredited.
For me personally, I trust Agilent know how to calibrate VNAs. There
is going to be more VNA expertese in Agilent than arguably any other
institution.
Thanks for posting those. It was educational.
I'm glad you found it useful.
Joe Gray
W5JG
Dave, G8WRB