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VRf - Calibration error

Question asked by VRFuser on Sep 2, 1997
In Response to:

> I want to make a full two port calibration whit a N-calkit, and
> everything seems ok until you'll select male or female port in the
> reflection  meny.
>I have came across similar problems with the HP8753 component driver.
>The solution I choosed was to implement the calibration sequence with
>direct I/O. In this case I was able to save and restore the
>calibration arrays to and from a PC and also make user defined cal kit
>How to do it:
>1.  Look in the examples in the programmers guide for HP8753 there is
    >an example how to perform a 2-por calibration and an example how
    >to read calibration data written in HP-Basic.
>2.  Make sure that all OPC-compatible commands are handled
>correctly. 3.  Make sure there is memory enough to store the
>calibration arrays in     the NWA.
Well, yes, there seems to be an issue trying to use the component
driver for 2-port calibration.  I see two things:  1) there is no "CALIFUL2"
driver command (CALIFUL2 is the HP-IB command that instructs the analyzer that a
2-port cal is beginning.  I think you can get away with out it, but I'm not
sure.  To be safe, use Direct I/O to send the command first, before sending the
reflection cal command "REFL".

2)  The Open command from the driver does an OPC?CLASS11A command (measure the
open), and awaits a response, and the Male command does an OPC?STANA command
that says measure the first standard (standard A) under the CLASS11A class
(opens for port 1 reflection in this case).  But their should be only one OPC,
not two.  In direct I/O the command would be "OPC?;CLASS11A;STANA;".  You are
hanging up waiting for the second OPC to return.

How to fix this?

>if You fail to handle the OPC commands the NWA will crash. There are
>quite some trial and error so be prepared to spend a couple of weeks
>with the calibration program.

A couple of weeks!!  I did it in 40 minutes while watching the evening news
and reading my young son a story. 

Of course, I've had a lot of experience.  One thing about OPC's:  for some
things, such as REFD (reflection done) or SAV2, (2-port cal done) it is better
to use SPOLL to read the OPC rather than enter the OPC, as the time it takes to
do the computation can change with number of points, etc.  By using the SPOLL
you don't have to worry about timing out.  I will include this in the program I

I will post an HP-VEE program that does a complete 2-port calibration.
Watch for it soon (today, or maybe tommorrow).  The programs' done, I
just need to get someone in our Network Analyzer support group to agree to
answer the questions that it causes.  .

Joel Dunsmore