measure current continuously with Keithley 6517 electrometer

[DDK_Salem]

Hi

I have a Keitley 6517 electrometer in my lab that i need to use for my experiments to measure the current continuously across polymeric films. i have the necessary hardware NI 488 GPIB card, that I purchased and installed.  I need to measure corrent across time, current vs voltage, so  I need a program continuously instead of a multiple readings and record them in a excell sheet and simultaneously graph it.

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,

Salem

Mensaje editado por DDK_Salem

[DDK_Salem]

sorry

I need to measure corrent across time, current vs voltage, so  I need a program continuously instead of a ""multiple"" readings and record them in a excell sheet and simultaneously graph it.

Mensaje editado por DDK_Salem

[GovBob]

DDK

 Just a couple questions. Are you trying to program an application to do this or are you just using the Kiethley .llb you mentioned? If you are trying to program the application what language are you using? LabView? LabWindows/CVI? Something else? Which version of programming language are you using?

 I don't have the hardware you are using but if you are using LabView I might be able to help a bit.

[DDK_Salem]

i use labview 7.1. hardware is a keithley KUSB-488A 

[GovBob]

Ok if you open MAX (Measurement & Automation) and click on Devices and Interfaces>>GPIB do you see the Keithly instrument listed? If you do you have established communications with the instrument.

Give me a few minutes to find you a good example that you can base your program off of. I think you need to understand shift registers and arrays to do what you need to do.

[DDK_Salem]

i have comunication whit the instrument and its well, just i dont know how modificated drivers from kaithley.

i am looking for someone to have this program, i checked forum and there is a similar case,  someone needs mesureament continuously voltage, but i need continously current.

[GovBob]

In the Kiethly .llb does it have a VI to read current? If so put that in a while loop and feed the output to a tunnel on the edge of the loop. Right click the tunnel and set it to autoindexing. This will create a array. Put your initialize VI outside of this loop (left side) and feed its error output and session to the current read vi. Put the close connection vi to the right of the loop and feed the current read vi's error output and session number to its inputs. Be careful though because the loop will go as fast as it can and eventually the array will get so large that your computer will run out of memory. You should put Wait (ms) function and wire 50 ms to it so that the computer will have time to respond to other things (such as your stop button).

A basic example to follow would be help>>Find examples. Browse>>Hardware Input and Output>>Modular Instruments>>NI-DMM(Digital Multimeters)>>Acquiring Waveforms>>Fetch and Graph Waveforms.vi. This does not use autoindexing but it gives you an idea on the order. If you have more problems following this just try to wire something up and post your question.

[GovBob]

Ok I downloaded the driver for your instrument and I can see your confusion. So open the Keithley 6517 example. Save it under a different name. Now you will need to modify it to do what you want. Click on the arrows on the top case structure until you reach 1. Right click on this upper case structure and select remove case structure. Now on the lower case structure click the arrows until the True case is reached. Again delete the case structure (not just the case) and replace it with a while loop. Delete the build array and replace with a wire to the loop. Right click the tunnel and set it to autoindexing. Mine looked like this when I was done.

[DDK_Salem]

hi! again

i got the previousprogram, thank you. now i have a new problem about write data to a spreadsheet file in the same file, when i try to save a few measurementes, i cant.

can you take a look?

thanks again

[ibecerra]

Hi

I noticed that your program had an error. The Vi that you were using to create the spreed sheet file (Write to Spreadsheet File.vi) receives a 1D or 2D array as input so the output tunnel of the while loop where you are storing all the readings must have the indexing option enabled. You can do this by pressing right click over the tunnel and selecting enable indexing.

In the other hand if you want to continuously write measurements to a single file I recommend you to connect a static path for the file path and connect a true constant to the terminal called “append to file?”.  Both things in the Write to Spreadsheet File.vi VI.

I attached you some examples.

I hope this helps.

Israel B.

AE Mexico.