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Wave-like noise when measuring 4-wire resistance with 2450 SMU

Models 2400, 2401, 2410, 2420, 2425, 2430, 2440, 6430
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Joined: November 25th, 2021, 12:23 am
Country: France

Wave-like noise when measuring 4-wire resistance with 2450 SMU

Post by cnicollet » November 25th, 2021, 1:13 am

I have been trying to measure high resistance samples (1MOhm) in 4-wire with a 2450 SMU, supplying current (0.5 to 1 µA) and measuring voltage (500-1000 mV). My issue is that I get a consistent wave-like background noise, that has a period of around 20 seconds, and I don't know where it comes from. To try and narrow down the possible sources of this noise, I made a mock-up resistance of around 450 kOhm with four BNC plugs soldered to it so can connect my 2450 to it with BNC to banana cables on the front panel.
The noise still appears with this dummy resistance so it is definitely coming from either the instrument, or the connections.
Then, I tried to measure the dummy resistance either in in remote control on a pc (with a usb connection cable) with a simple labview code (with the keithley 24XX driver) or directly on the instrument (local control).
It turns out that the noise disappears when I measure without the remote control. So it seems that the problem comes from the remote control but I can't really figure out how this is possible. Has anyone here had similar issue with their measurements?

I also tried the same labview code with the addition of a default filter (type: repeating, number of filter reading:3), which attenuates the noise but doesn't suppress it.

The only difference between the remote and local control that I can see is that with the remote control I do one measurement every 500 ms whereas for local control I run the continuous readings. Could the problem comes from the trigger function somehow?
Attached is the measurements I get in remote, remote with filter, and local, and a screenshot of my labview code.

Any help with this will be much appreciated.
labview without filter.png
labview without filter.png (129.25 KiB) Viewed 34 times
wave noise.png
wave noise.png (124.86 KiB) Viewed 34 times

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