FIMV and external voltage source

jaromir-sukuba / J-SMU

DIY source-measure unit

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FIMV and external voltage source #1

Open 64-32-16 opened 4 months ago

64-32-16 commented 4 months ago

Hello Jaromir,

there is a problem with the crossover in the current circuit. In FIMV mode and an external voltage source, the current goes to max.

I've already tried to find a solution. Unfortunately, my solutions do not have good control properties.

Can you take a look at this problem?

Thank you very much

RikVervenne commented 4 months ago

As I understatement your explanation thuis is probably noten issue. In FIMV the voltage compliabce limits the allowable output voltage of the SMU. When an external voltage is applied in this mode smu compensates this by outputting the voltage necessary to compensate this such Thatcher the FI is reached. However, if the needed compensatie exeeds the compliance, regulation is impossible.

64-32-16 commented 4 months ago

Yes I agree with you. I'll put it differently. Is there perhaps a protective circuit if Limit < Uex, otherwise the measuring resistors will be grilled. Possible solutions:

Increase limit automatically?
current protection for each range?
automatic cut off?

Thank you for your feedback

RikVervenne commented 4 months ago

Autoranging is not -yet- implemented by Jaromir. current protection may be practically impossible I guess. Cutoff might be possible. I wonder how this works on a Keithley or something... I suppose Jaromir has more important things on his mind for the moment....

jaromir-sukuba commented 4 months ago

Hello Jaromir,

there is a problem with the crossover in the current circuit. In FIMV mode and an external voltage source, the current goes to max.

I've already tried to find a solution. Unfortunately, my solutions do not have good control properties.

Can you take a look at this problem?

Thank you very much

Hello, I may need more details about it. Did you find the problem in simulation or real hardware? Post your simulation file or write down the procedure to reproduce your findings, please.

64-32-16 commented 4 months ago

Currently I only use a simulation. problem description: With an external voltage source in FIMV mode and Limit < Uex, the current increases to max. I understand this problem, but a protective circuit makes sense here.

Raise limit automatically.
- automatic switch off. I don't own a Keithley. How is this problem solved with the Keithley? Thanks for your support. Andreas Wichmann

64-32-16 commented 4 months ago

Hello jaromir, I would be happy to send you my simulation. Unfortunately I can't post the file in the github comment. I'm not at home at the moment. Here is my email anwichmann@outlook.com, if you need my simulation, write me a quick email. Thank you very much

jaromir-sukuba commented 4 months ago

I'll request the file my the e-mail and see.