Instrument Control (GPIB, Serial, VISA, IVI)

Showing results for 
Search instead for 
Did you mean: 

HP8757 Scalar Analyzer

Go to solution

Dear colleagues,

I have prepared the 8757 control software, it is rather complex. Unfortunately, I have problem with reading data from 8757. All setup works fine, 8757 sends the data block. After it shows on screen that the "data dumping was completed" the machine freezes and does not react to any control string via HPIB. I use LW Visa read and write instructions.

I am calculating the number of bytes to be read as number_of_meas_points x 8 bytes_per_point


0 Kudos
Message 21 of 34

Hi Ivan_Ryger,


Can you attach a screenshot of your VI or the VI itself? Additionally, can you post a screenshot of the problem you're encountering?


In the future, you might get more of a response if you create a new forum post with your question. This forum is 3 years old and will not be seen by as many peole as a new forum post would. 




Kelsey W.
National Instruments
Applications Engineer
0 Kudos
Message 22 of 34

Dear Kelsey-W. Fortunately, I found the mistake and now the algorithm works fine. The problem was that the HP8757 does not send Number_Of_Points x 8 Bytes_Per_Point.

At the end of transmitting process, it sends one more byte that I did not count on with. For this reason also the above mentioned does not work correctly. After two read-outs it freezes also.

I attach the screenshot of read-out process. I added 10 extra bytes to see what really commes from the GPIB bus.


0 Kudos
Message 23 of 34

Hi Ivan_Ryger,


I'm curious about the coercion dot on your VISA Read function. Is it possible you're passing an array instead of a scalar as the number of bytes to read? What data type does it say is being passed to the VISA Read function as "bytes to read"?


Have you looked at the other examples on this discussion forum? "Sloppy" posted one on the second page that you might find helpful.



Kelsey W.
National Instruments
Applications Engineer
0 Kudos
Message 24 of 34

Thank you for your answer. As I have mentioned, the algorithm already works. I do not pass array to determine number of bytes to be read. I withdraw only one scalar number from this array according to number of measurement points.

0 Kudos
Message 25 of 34


I am also using an HP8757, with some Labview code. But I am struggling to connect a HP8350 sweep oscillator to my system. However I connect the various wires at the back of the two devices, I cannot get NIMax to recognise that both exist at once. Can anyone who has used this system help?

0 Kudos
Message 26 of 34

If the 8350 is connected to the System GPIB instead of the HPIB the 8757 is the 8350 controller. In this case you will not see the 8350 on the GPIB bus. You will also have to talk to the 8350 thru the 8757 in pass thru mode. See the manual for more information. Also a note for the origional poster. The OPSP command is not a SCPI type command it is the old propietary syntax NP used in the old days. OP stands for Output Parameter make the command after it a query.

0 Kudos
Message 27 of 34

When I address the HP8350 Source, the system times out, and Data PassThrough Executing simply stays on the SNA screen. Any ideas why that would be the case? I am guessing it isnt Labview related, but people here seem to know what they are talking about.

0 Kudos
Message 28 of 34

Hi Donalbain,


It appears that this thread was created back in 2010.  To ensure that you get maximum visibility from our engineers and customers, as well as to help us keep track of the volume and types of issues that come through our forums, it is recommended that you create a new thread to address the problem.  You are welcome (and encouraged) to link this thread in your new post if you feel that will better explain the situation.


Have a great day!



Applications Engineer
National Instruments
0 Kudos
Message 29 of 34

How are you making the call. You will not be addressing the 8350 address of say 19. You have to put the SNA in "Passthru Mode" and the address device 17 or 1 above the SNA address of 16(the typical default address of the SNA). Your call to the 8350 would then be to the SNA Passthru address using the 8350 command as usual.

0 Kudos
Message 30 of 34