GPIB error -1073807339 when trying to read from a device

[dark7flame]

Hi, I'm using Labview and GPIB to control a very outdated Temperature Control device.  I can remotely control it's operation just fine, my problem comes when i try to read the sensor data.  The Manual for the TC device indicates that the command for reading the temperature off of the device is "WSA"  which i input as a command in my vi.  Generally, this gives me the temperature readout the first time around, but gives the error -1073807339 when the program loops or when i run the program again.  This isn't a large amount of data, simply 7 bytes.  The error indicates a timeout error, but I already have all of the information that I need!  How do I set up my vi/hardware configuration in order to eliminate this error and constantly update my temperature readout on the display from my vi?

Any and all help is appreciated,

Benjamin

[Albert.Geven]

Can you attach your vi's?

Maybe you need to read more than 7 bytes or trigger again?

[dark7flame]

Here are the vis.  From what I understand, I either need the TC unit to stop sending data (blank characters) or the GPIB to stop looking for data, therefore preventing a timeout.  The number of bytes is hard coded in the query.vi, but I have changed that number higher with no effect and lower with only the effect of rastering the data.

[Dennis_Knutson]

I don't understand your comments. Why do you think the instrument is sending balnk characters and if you don't do a VISA Read, you can't get data from the instrument. You may be getting a timeout because you are requesting data to fast. Try putting a delay after the configuration commands and another delay after the output request command. All of this assumes that the command you aer sending are correct and you have not placed the instrument in some kind of error condition. You should be able to debug all of this in MAX. After configuring it, just do a WSA query over and over.

[dark7flame]

When I use the "Measurement and Automation" program to input the command directly to the device, if I use other commands, the instrument responds in the proper manner.  When I use these other commands in labview, i also get it to behave in the proper manner.

The Query subvi has a write command followed by a read command, which for other instruments has worked fine up to this point.  but if you can see a problem with it, please let me know.  i would be happy to improve my code.  so there is a read command in there, it's just under a subvi.

Back to the WSA command.  when i put it into the "Measurement and Automation" program, just the command, I get my sensor data and then 30-50 blank characters followed by a timeout.  So I know that the device recieved the command to send the data, and that it responds to the command correctly.  it sends the data and then a series of blank characters, as described in it's manual.  i also know that the GPIB recieves that data, otherwise it would not show up in the "Measurement and Automation" program.  It's just the fact that it times out, like the GPIB doesn't know to stop collecting the data.

What's this MAX program? can u link me to it?

[Dennis_Knutson]

First, MAX is Measurement and Automation Explorer.

It sounds like the instrument is not compliant with IEEE-488.2. With a compliant instrument, the EOI line is asserted at the end of a data transmission and an instrument would not be sending blank characters. That means that you do not need to know how many bytes the instrument has available. You just have to request some large number and the VISA Read will automatically terminate. In MAX, you can change the default behavior so that a read will terminate on an EOI or another character. With the GPIB functions, you also have this option with the Mode input.

[dark7flame]

When I use MAX to try to interact with the instrument I get the following picture.  This is the same result when I have the any of the configurations in the "Configure EOS" menu selected.  If I use the termination byte from the TC's manual, I don't get any response from the machine and i just get blank spaces and then a timeout.

I apologize, i should have put this picture in my first post.

[Dennis_Knutson]

What is the termination byte? Can you attach the manual?

[dark7flame]

here is a link to the manual.  the termination character and other commands are in section 4.0 and following.

http://www.lakeshore.com/pdf_files/Obsolete/DRC-91C_Manual.pdf