Instrument Control (GPIB, Serial, VISA, IVI)

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RS232 Communication with JEVAmet VCU (Vacuum Control Unit)

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Hi All, 


We got in our lab a new pressure gauge JEVAmet VCU from JEVATEC company. This device allows cummincation through RS232 interface. I connected that device using RS232 cable to the PC and then, used a labview example (Continuous Serial Write and Read) to read the version number of the pressure gauge as a simple request, however, I always get the same error

Error -1073807339 occurred at VISA Read in Continuous Serial Write and

Possible reason(s):

VISA: (Hex 0xBFFF0015) Timeout expired before operation completed.

(see the attached photo). You can find the manual of such a device to check for the string command here 

My attempts to solve the problem:

1- increase the timeout duration ------- failed (increasing the timeout did not solve the problem)

2- Changing the port instead of RS232 to convert it to USB using RS232 hub ---- failed

3- restart the device ---- failed

4- Changing the baud rate and check the new baud connection ------ failed

5- Check for the code display ----- failed 


What is the problem I am facing here?

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Message 1 of 4

In your left frame, \n is the termination character.  In the right frame, you are using the \r as the termination character which will cause a timeout as the command is not terminated properly.

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Message 2 of 4

I changed it but it still timeouts. I also used NI MAX for VISA test panel and it shows the same response.

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Message 3 of 4
Accepted by topic author AchimKittel

1. Your string control has a display mode of "Normal".  Therefore your "\n" is NOT a carriage return.  It is 2 bytes: '\' and 'n".  You should change your display mode to be "\ Codes" and then your "\n" will actually mean carriage return (after you get rid of the extra '\').

2. It looks like you have the "End Write on Termination Character" set to TRUE.  Therefore, you do not need to have the termination character (the "\n") in your command string.  VISA will add it for you.

3. The Continuous Serial Write and Read example is BAD.  I suggest using an Event Structure to send the data and immediately read the response.

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Message 4 of 4