Calibrating a network analyser...

There is a website vnahelp dot com that may have some good information.

Good luck, Dave

Reply to
onyx49
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Ours (well I mean the one we have at work, a slightly newer rig) has

4 things that plug in, a short, a known 50 ohm terminator a "open" and a known cap value. the rest is in the software.

Steve Roberts

Reply to
osr

don't twiddle any pots inside!!!!!

get some standard test loads...

if you don't care about great accuracy, make a homemade open, a short and a good 50 Ohm load

you should be able to calibrate the instrument with those by pressing the correct buttons on the front panel...

do not turn any posts inside...

Mark

Reply to
Mark

"Calibration" usually means that you send the instrument off to a metrology lab and they do some testing against traceable standards and make appropriate adjustments/corrections and put a sticker on it and send it back.

In the network analyzer world, "calibration" usually means the measurement of local standards prior to performing measurements and "verification" is the process that the metrology lab does.

When I was last employed, rather than send "my" HP8510 to Metrology, I performed the verification using traceable standards and HP software. I provided the data to Metrology and they gave me a "calibrated" sticker.

When I first acquired the instrument, NBS (now NIST) would not even certify 3.5mm (precision SMA) standards, so technically, I wasn't supposed to do production testing with my "uncalibrated" '8510 using

3.5mm standards.

Ideally what you need are:

1) One (or two) short circuits in the connector series that you are using.

2) One (or two) shielded opens in the connector series that you are using.

3) One (or two) precision terminations in the connector series that you are using.

4) At least one 10, or better, 20dB precision attenuator in the connector series that you are using.

All analyzers have some systematic errors that are determined by measuring standards with "known" responses. For example, a short circuit should have 100% reflection and 180 deg phase shift. If you don't measure this then there is an error that can be determined and corrected for.

For reflection measurements, it takes at least three standards to determine the systematic errors. For transmission measurements, it takes at least one more (a through connection).

Automatic analyzers have all of this stuff built-in as firmware or software.

Once this pre-measurement calibration is performed then you can do verification by measuring other known standards. H-P used precision attenuators and air-lines with and without stepped diameters that gave known reflection coefficients and phase shifts.

You can likely get by with one short, one precision load and a decent attenuator.

For frequency calibration, a check of the timebase oscillator should suffice. Power calibration is usually unnecessary unless your are measuring active devices that are drive level sensitive.

I wouldn't "twiddle" anything without some really good standards and other appropriate test equipment.

Reply to
Wes Stewart

Hi everyone,

Well I bought this VNA (picture posted to abse under "network analyser") and I guess it needs calibrating since the last sticker was dated 1998! It covers 4Mhz - 1.3Ghz, BTW. So I suppose I could get some chap in from HP on 3x10^726726 pounds/hr _or_ do it myself. It's not as if I need anything super-accurate, after all. I'm only a hobbyist and will only be goofing around with it. So I thought maybe I don't even need to borrow some other piece of expensive junk with a calibration certificate to check it off against... How about this idea? I cut say four lengths of 50 ohm feeder to exactly quarter wavelengths (factoring in appropriate velocity correction to the cable lengths concerned) at say 25Mhz, 200Mhz,

600Mhz and 1200Mhz. Then I hook these up in turn, whip the lid off and twiddle the calibration pots to show the 'right' trace positions for each corresponding frequency. Then I short the ends out and re-twiddle for a right-angle phase shift. Would this work? I can't think of a more absolute frequency standard than a simple specific length of feeder. But OTOH, I have been known to talk a bunch of crap and maybe there's a big snag in this seemingly ingenious work-around that hasn't occurred to me. What thinketh the Panel on this idea? Thanks, p.
--

"What is now proved was once only imagin\'d" - William Blake
Reply to
Paul Burridge

Paul Burridge wrote in news: snipped-for-privacy@4ax.com:

Isn't there a published cal procedure with listed standards for this instrument?

--
Jim Yanik
jyanik
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Reply to
Jim Yanik

IIRC our test sets costed something like $2500.

Some time ago I made a few test sets for in-factory calibration of network analyzers (never give out your shiny new test sets :) ). Nothing too special, only thing was to use multiple resistors to get a 50 Ohm termination plug. Calibration was very easy via the built-in functions, no manual needed.

greetings, Michiel

Reply to
Michiel

You do not want to adjust any pots if it is a computer-controlled type network analyser.

I think you might like to read the many application notes that you will find on this subject on the Agilent website. Even if they are not written about your specific model of analyser, they will give you some useful ideas.

Chris

Reply to
Chris Jones

to abse under "network

last sticker was

could get some chap in from HP on 3x10^726726 pounds/hr

It's not as if I need anything super-accurate,

and will only be goofing around with

need to borrow some other piece of

certificate to check it off

lengths of 50 ohm feeder to

appropriate velocity

200Mhz,

and

corresponding frequency. Then I short the ends out and re-twiddle

right-angle phase shift. Would this work? I can't think of a

frequency standard than a simple specific length of

been known to talk a bunch of crap and maybe

seemingly ingenious work-around that hasn't

Panel on this idea?

You do not want to adjust any pots if it is a computer-controlled type network analyser.

I think you might like to read the many application notes that you will find on this subject on the Agilent website. Even if they are not written about your specific model of analyser, they will give you some useful ideas.

Chris

Reply to
Chris Jones

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