Labview 8/Keithley error

[jeff137]

Hi all,

In my experiment, I am running a voltage through a transistor (using a Keithley 6487 picoammeter), and collecting the resulting current. A Labview program automates this whole process so that I can run any number of voltages and collect the resulting current; all of these measurements are then put into an excel file. This was developed by a past student, but no longer works properly as all the computers here have been replaced. The error I run into is error -410 on my Keithley 6487 picoammeter, this means that a Query was interrupted. I'm guessing that this has something to do with the Labview program (particularly the subVI that I created; it's task is to collect the current data), as it keeps sending commands to the picoammeter when it hasn't completed the first command sent. I am still able to see all the voltages in one column of the excel file, but the other column that should display the resulting current shows 0 for every cell. Anyone want to take a stab at this? Should I be adding a time delay to any of the frames? Outside of the subVI (icon = Keithley 6487 in VI diagram attached), the rest of the VI is functional. Your help is very much appreciated and you will be receive due credit in my work. I've attached the VI and subVI to this message. Thank you everyone!

[Ebele_Obijiofor]

Hello,

From what you said in your post, it does look like you need some delays between your write commands. It looks like you have some delays already, but you might need to increase them to give the instrument enough time to process one command before you send another. Hope this helps.

Regards,

[jeff137]

Dear Ebele,

Thanks for your reply. I've tried adding more of a time delay to the subVI's GPIB Write operators but the program is still not working. I know I'm communicating with the picoammeter, and I can see the current reading on the actual panel of the picoammeter, but this current value is not being returned to Labview (the value should be displayed on the front panel of the subVI, but it remains blank). Any other ideas? Thanks alot for your help. 

[Ebele_Obijiofor]

Hi Jeff,

Are you getting any errors in LabVIEW at all? You could try talking to your instrument in Measurement and see if you receive your values correctly. It is possible that you may need to increase your delays. If you modify your program (or create a simple VI) to write and read just once, are you able to get any data? Hopefully some of these steps will help pin down what the problem is. Thanks!

Regards,