SMU (PXIe 4136) as a DC Current Source

[michberk]

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

[Basjong53]

Can you post the VI for LabVIEW 2018?

How is your physical electrical circuit? You can't push a current without a load.

[michberk]

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?

[Basjong53]

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.

[michberk]

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

[Basjong53 · Accepted solution]

Glad you figured it out!

To disable the current, use this function: