Read Keithley2700 data from Labview 8

[DGU]

I downloaded driver from NI website and when I tried them out, I found that most part of the driver are working, for example, I can initialize, I can set digital line. However, when I tried to read out single measurement, I found some problem. In driver example file: ke27xx Single Measurement Example.vi, then further inside ke27xx read single point.vi, I put a probe on visa Read output. Suppose the measurement should be 12.345, but the probe sometimes show 1.2345E+, sometimes show 1.2, and sometimes show 1.2345E+1ADC324 with many trash behind. As you can imaging, the numeric output stays between 1 and 9.9 most of time.

Anyone out there had the same problem?

Thanks in advance for any advice.

[DGU]

I am using GPIB. But I checked initialize.vi, it has a lot of serial stuff, like Baud Rate, Flow control... Could this be the problem?

thanks,

[dpacaba]

Hello DGU:

I think the expected value read should be 1.2345E+1.
Is the probe you mentioned connected to the string "read buffer" output of "VISA read" vi?
If yes, there's something wrong with your communication through your instrument.  You might want to check-out first communicating with your instrument using MAX.

I hope this helps.
Please advice if you have any other question.

[DGU]

Here is the strange thing. I can't even see the instrument in MAX. I can't even scan for the GPIB address. I can only get it on keithley 2700 front panel.

the card is Keithley CEC488. I downloaded and installed driver from keithley website.

I checked manual, the ASCII data format suppose to be:

+1.23456789E-03VDC, +11.664SECS, +236RDNG, 000, 0000LIMITS

readings               units   timestamp         reading #    chan#, limits code

but I only see the first 10 bytes or so.
                                                                        

[Dennis_Knutson]

It's not strange that you can't do anything in MAX. That is for NI cards only.

On the read, how many bytes are specified? Putting some large number here is usually not a problem since theread will terminate whenever the EOI is detected. Does the instrument driver you downloaded use VISA or traditional GPIB calls?

Message Edited by Dennis Knutson on 01-26-2006 01:45 PM

[DGU]

I tried to read 100 bytes, more than enough. I am not sure what's traditional GPIB call, the driver use VISA Read and VISA Write everywhere.

[dpacaba]

Hello DGU:

It is more like an old way of communicating with a gpib card.
Have you tried installing the driver provided by CEC?  Probably they have their own functions to communicate with their gpib card.
If their functions are written in C, then you could use CIN's to communicate with their card instead.

[DGU]

I actually only use keithley CEC488 driver. I first used version 7.0, then tried version 8.0 later.

I did find some solution. The original driver use READ command to read data. I changed it to MEASure. MEAS will give me right answer most of the time, cutted answer still happen once a while, but it is much better. The problem with MEAS, though, is the program runs very slow. We had VB code to run the same process (VB code has some issue, that's why I want to change it to Labview). The Labview code run 3 times slower than VB, which is not acceptable.

BTW, a note from user's manual about MEAS: this query is much slower than a :READ or FETCH query because it has to reconfigure the instrument each time it is sent....

[Dennis_Knutson]

I don't think your problem has anything to do with LabVIEW. It could be your VISA installation and/or the setup of the CEC card. Are you running NI-VISA or a VISA from Keithley? If you're running NI-VISA, what version? Do you have the tulip passport enabled? This is usually required and set from MAX. Expand the software listing, select NI-VISA, and go to the VISA Options tab. Did you get 488 (not VISA) functions for the card that you can try? The only other posts in these forums about CEC cards refer to using function calls from a CEC driver and not VISA. Did the VB code use VISA calls as well? What does Keithley/CEC say about setting up their card to work with LabVIEW?