Continuous Measurement with Keithley 6517 electrometer

[Sulpha]

Hi

I have a Keitley 6517 electrometer in my lab that i need to use for my experiments to measure the DC voltage continuously across a capacitor (Sawyer tower circuit),unless I want to stop in the middle. I also have the necessary hardware NI 488 GPIB card, that I purchased and installed and I downloaded the necessary VI's from the website. I did a dry run to check if my instrument talks to my computer by plugging in a constant dc source to the equipment and running from the single read example VI. It measured perfectly and gave the reading on the computer as 1.5 E+1V. Now, I need to measure a very low frequency 0.01Hz signal across a capacitor, so  I need to run this program continuously instead of a single read and record it in a excell sheet and simultaneously graph it as a function of time. As my background is not in programming I find it difficult to do this. I know that it is just a simple while loop we need to add in the single read example VI, but I do not have a clue of where to put this while loop, since, i do not want to configure the equipment (like zero check ) everytime the loop runs. I have attached the keithley.llb file. It will be great if some one can help. I really appreciate it. Thanks a lot for the time.

Sincerest Regards,

Manoj

[Dennis_Knutson]

I've cleaned up the example you mention by getting rid of the stupid sequence structure and added a while loop around the read and parse. I wired a chart to the measurement and added a Write to Spreadsheet to record the results after the while loop stops. I've posted it as version 7. That's the latest I can save to right now. I've also attached a picture with the mods I made. If you need it in version 6.0, maybe someone else can do the conversion.

[Sulpha]

Thanks a million Dennis. That was quick.I really really appreciate your help. I will go and test program and let you know if I run in to a problem.

Sincerest Regards,

Manoj

[Sulpha]

Hi Dennis,

I hooked up a low frequency sine wave signal to the electrometer so that the file you sent would plot a sine wave inthe graph. But for some reason it did not run continuously, again, it just showed the first reading it took in the measurement value. Please let me know on this. Also, how fast will it take the readings? Can I change the time, i.e. the number of points it will take in a time period. If you could help me on this it will be great. I am also using 7.0 version. Thanks once again for your help.

Sincerest regards.

Manoj  

[Dennis_Knutson]

Sorry, the while loop conditional terminal should be set to Stop if True. Right click on it to change it. The way it is now, it will take readings as fast as possible. You can modify the time by putting in a Wait (ms), Wait Until Next ms Interval, or Delay function. All of these are on the Time & Dialog palette.

[Sulpha]

Thanks Dennis, I just figured that out and I wanted to post a reply, but you got to it first. I have another question, All the data are put in a single row in a txt document, is there any way that i can put them in a single column, instead of a row, so that i can transport that to excel and generate the curve. Also, the VI you sent, will it be useful only for DC voltage or can it also be used for measuring resistance, charge etc (since there is a multi line string at the very start) I am kind of confused on this because you said that you have deleted some of the functions from the original VI. Please let me know on this. I am really grateful for your help.

Sincerest Regards,

Manoj

[Dennis_Knutson]

If you want the results in a single column, all you have to do is set the transpose? input of Write to Spreadsheet to True. Excel will import the file either way.

I didn't really delete any functionality. All I did was move the code in the sequence structure out of it. The sequence structure wan't doing anything except hiding code since all of the error inputs/outputs were already connected and that's better than using a sequence to control execution flow. Plus, the sequence structure made it impossible to put a while loop just around the read because the change of the zero check was inside the sequence.

If the VI worked before by changing the function control on the front panel, it will work after the mod.

[Sulpha]

That makes sense Dennis. I really appreciate it.

Sincerest Regards,

Manoj

[Sulpha]

Hi Dennis,

I would like to give credit for your help in the LabView programming in my PhD dissertation, it will be great if you could email or post your full name and your affiliation. Thanks a lot.

Sincerest Regards,

Manoj

[Dennis_Knutson]

I'm flattered but I'm a bit hesitant to publish my email or any other personal information in a public forum and frankly, I would prefer that you thank the entire community. I did nothing that an awful lot of other people do each and every day.