Problem between Labview and Keithley 2602A

[FrenchLizard]

Hi Everyone,

I think my question is a little bit stupid, but I really don't know what the problem is. I simply wanna read my current from my solar cell by changing the level of my voltage to obtain an IV curve, which is normally pretty easy. So I created a loop, where I increase my voltage step by step, and used a VI function from the Labview library which connects the Keithley and Labview together, named "Keithley 2600 Series.lvlib: Source Level.vi". I start at 0, and increases it by 0.01 volt each time. If I use the Highlight execution, I can clearly see the value is correct, and if I go inside the SourceLevel VI, I can clearly see the command string: "smub.source.levelv = 1.6" for example, if I want to set my voltage at 1.6V. The picture attached shows a part of my code.

Despite of all of this, it is obvious the Keithley doesn't react correctly. It only works volt by volt, setting 1V,2V,3V, etc.... but never the values between. My IV curves are ok to read the Isc, but not the Voc. Does this ever happened to any of you? I would be really happy to understand what am I doing wrong, because it seems pretty easy to solve. 😕

Thank you so much! 

[RavensFan · Accepted solution]

It's kind of hard to debug a picture of a tiny portion of code.

But I'm going to take a guess at what I do see.  Your one constant shows a 0,01 (comma).  So I'm guessing you are in a country that uses a comma instead of a decimal point.  I can't see what goes inside the Keithly code, but I'll make a guess that it is doing some conversions where it expects the decimal point to be a period.

Take a close look at the Keithly code and see if that explains it.  Try setting your PC to use a period for the decimal point and try running your code again and see if it works better.  It's possible that the Keithly conversion is using a system setting, rather than using a decimal point which is what your one sentence says it is sending.

[FrenchLizard]

Thank you so much! I knew it was really easy to solve. You can't imagine how many times that happened to me before, being a french working in North America is so annoying when it's about coding. 😛 Cheers, and thanks a lot!