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08-29-2023 09:25 AM
Hello everyone,
This is a project that I have inherited and I don't have much experience with SMUs.
I'm trying to use an SMU to get a DC Current. The current value can be changed and I would like to be able to turn the source ON and OFF.
The code that I'm using (attached here) is not mine. I get that it configure the Source and then it reads from it but this are the problems that I've encountered so far:
1. When I send the value I want to get (0.003mA and the Vlimit = 20V) just after opening the communication path, the SMU doesn't return the right value. It returns a small current value (1e-7) and it says that the compliance/limit is reached.
2. If, instead, I sent first 0A and 0V limit I receive the following error:
Invalid value for parameter or property.
Device: SMU4136
Property: Voltage Limit
Requested Value: 0.0
Maximum Value: 200.0
Minimum Value: 6.0e-3
But after that error, when I send the usual 0.003mA and 20 V, I get the exact value!!
So my questions are:
how can I make the SMU to return the correct value right from the beginning and how can I turn the source ON (value different than 0) and OFF (0) without getting the previous error.
Thank you in advanced
Solved! Go to Solution.
08-29-2023 09:40 AM
Can you post the VI for LabVIEW 2018?
How is your physical electrical circuit? You can't push a current without a load.
08-29-2023 10:09 AM
I attach here the subVI in LV 18. I know that you cannot push a current without a load... What I'm wondering is why when I sent the current value that I want it doesn't work, sent 0 and get the error, and sent the current value again, this time works.
I think that is independent completely to my electrical circuit. Why the first time doesn't work and after the error it works?
08-29-2023 10:52 AM
Sorry I misread your question.
Can you try to add the DCPower Commit.vi function just before DCPower initiate.vi. The error you get is correct, you cannot set a limit of 0V.
Btw, you don't have to manually set the precise current level range. If you set 5 mA, it will automatically round up to the nearest valid range (10 mA in this case). So you can remove those case structures.
08-30-2023 08:45 AM
Hi,
Thank you so much for your input. I figure it out what it was... You were right about my circuit setup. I didn't realize that after the set up of the current some relays were closed to have some resistance. That's why the second time I always got the right current but never the first time.
One last question, how could I turn off the current source then? If when I sent 0A it gives me an error.
I will also remove the case structures
08-30-2023 09:31 AM
Glad you figured it out!
To disable the current, use this function: