Oxford Mercury series instruments : Works with NI-MAX but fails with Labview

[kanti.dasgupta]

Hi,

  I am trying to interface an Oxford Instruments "Mercury Series" power supply for superconducting magnets, I am using Labview 2013 and an NI USB-GPIB-HS.

The problem I have is the following:

1.  After connecting the instruments I run NI-MAX (ver 14.0) to check that the instruments are recognized by the GPIB-bus. Everything goes fine, the instruments are detected and I can communicate with it by typing commands in the 488.2 communicator. Read and write both work fine.

2. Then I try to write my own code in Labview to run the instrument.  The standard 488.2 commands Send/Recieve or GPIB-Write anf GPIB-Read do not work.

There are other instruments on the same bus also - which work fine with both NI-MAX as well as my vi-s from Labview.  I have tried doing the "obvious" things

like intialising the GPIB before sending any command and then do a Device Clear for the specific instruments before sending other commands.

3. So the question is : What can be the reason for an instrument to respond correctly via NI-MAX but fail to do when addressed from Labview with essentially

similar basic commands?

I have tried tracing the origin of the errors via I/O trace (NI-spy), but they didn't help in locating the precise problem.

Would be grateful if somebody could suggest an answer.

Have other people faced this before?

Thanks-

Kanti

[Dennis_Knutson]

You have not provided your code, exactly what you sent in MAX, or the I/O Trace file. I'll make a guess that it's an older instrument that requires a cr or lf termination.

[kanti.dasgupta]

The instruments are actually newer  (rather than an older version). You are correct that they need an extra "\n" after the command string - which I had provided.

The command tryped in NIMAX was simply  "*IDN?\n"   in response to which  the instrument sends its identification string correctly. 

All other commands also worked properly.

I then tried the same in Labview using   "Send" and "Recieve". The Recieve generates the error.

I am attaching the trace file (converted to txt) and the VI. Line 10-14 has the error.

Thanks

[johnsold]

You need to change the data string to '\' Codes Display before typing \n will generate a line feed.

Lynn

[Dennis_Knutson]

And in addition, any GPIB instrument that requires a termination character besides EOI, is not compliant with IEEE-488.2 so no matter how 'new' you think the instrument is, the firmware is incredibly old.

[kanti.dasgupta]

Checking the "\ Codes Display" fixed the problem. Labview now communicates correctly with it.

Thanks to Dennis_Knutson & Lynn! 

-Kanti

[Dennis_Knutson]

Why does the idn query return Stanford Research instead of Oxford Instruments?

[kanti.dasgupta]

I had a "Stanford Research" instrument also on the same bus - I was also sending a query to it as a check that the bus itself was not hanging.

So the IO-trace captured that also.