Graph received by Labview is different from the original on Vector Analyser

[ThuyHoai]

Hi everyone,

I'm working with Vector Network Analyser MS2026C now and try to get data via Labview. I would like to get the trace data of S21-parameter in Log Mag. In Labview 2017 there is an example calles "Anritsu MS20XX Series Acquire Trace.vi" in library.

Although I set up in Labview file, the graph type should be in LMAG, what I got from this example is different from the original trace, either the form or the value. Let say, the peak is around -10dB, but in Labview, it is in 0,26. I don't know which unit it is. If I  convert -10dB into linear value, it shoule be 0,316.  

I read the document of Anritsu and it says, the command/string ":FORM ASC" in subVI "Anritsu MS20XX Series.lvlib:Read Trace -> Anritsu MS20XX Series.lvlib:Fetch Trace" means, the Units are the current Instrument Units.

Could anyone tell me, where the problem is? Thank you for your help.

Thuy Tran

[Christoph_D]

Hi!

I would guess the questions should be directed to Anritsu since it is their driver you are running.

Best regards,
Christoph

[altenbach]

Can you run your VI so the graph contains data, then "right-click...data operation...make current value default". Copy it into new VI and attach it here. It looks like the data is all there, but maybe in an unexpected form. (derivative, interlaced, interlaced complex data, etc.).

I am not familiar with all the missing vendor subVIs. Are you sure you have configured them correctly? Are they stock or did you modify any of them? Where did you download them from?

[wiebe@CARYA]

The data looks like most significant and least significant data parts are interleaved... So, somewhere you get 1 hi byte and one low byte (or 1 hi word, one low word, etc.), and convert them both to floating point values. What should be done is that the to bytes (long, etc.) should be combined to one word (word, etc.) and then converted to one float as one.

Regards, Wiebe.

[altenbach]

This clearly happens inside the vendor provided driver (unless you made modifications!), so the suggestion to contact the vendor is a good one. Could it be that one of the configuration VIs allow you to set the format and you set it wrong?