PXIe-4163 current_limit_autorange seems doesn't work for low level current

[Onezhenji]

Hi guys,

these days i was doing some MOSFET idVg curves sweeping using PXIe-4163, as we know, for NMOS, when Vg is about 0 volt, id is very small, saying maybe 1nA or below, it turns out to several mA when Vg gets larger and larger. So I choose current_limit_autorange to switch ranges in measuring.
I found that the current resolution is not as low as my expect. When I use the fixed current_limit_range(set to 100e-9A), I got several hundred pA to several nA, but 10e-7A for current_limit_autorange.

[santo_13 · Accepted solution]

FYI - auto-ranging is not a hardware feature but a driver feature. Enabling Auto-Ranging will let the driver choose the current range to follow the current limit setting.

You need to use an advanced SMU targetted for device testing like PXIe-4137 that uses hardware-level auto-ranging.

[Onezhenji]

I do find a parameter called "autorange" in python's API of nidcpower, it seems that PXIe 4163 doesn't support this parameter.
So, 4163 can't satisfy my measurement requirements, right?

[Onezhenji]

Is there any way I can use PXIe 4163 to achieve my measure requirements in my topic?

[santo_13]

Yes, you can implement auto-ranging in software.

For every measurement,

• Make a measurement at a higher range
• Check measurement against the list of available ranges
• Choose a range that suits the measurement value
• Re-measure at the new smaller range
• After the measurement is done, go back to the larger range

[Onezhenji]

Well, it seems that I can not use sequence mode.

[santo_13 · Accepted solution]

Nope, software-level auto-ranging cannot work with sequence mode as the selection of the best range happens in the application and not on hardware.

[Onezhenji]

I updated nidcpower to the 2022 Q4 version, now PXIe-4163 supports auto-range. Thank u.

[santo_13]

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@Onezhenji wrote:

I updated nidcpower to the 2022 Q4 version, now PXIe-4163 supports auto-range. Thank u.

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Good to know that the latest driver updates the SMU firmware to support hardware level auto-ranging