Digital Multimeters (DMMs) and Precision DC Sources

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SMU used for current measurement

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I need to measure current in the range 5 to 10uA output by a current source pin. Usually I would have connected PXI4065 to this pin and measured current. But in this case the current to be measured is low.

I have SMU 4130 which has high current measurement accuracy at 200uA range (0.03%+0.02)uA .





Can I use the current measurement part of the SMU (CH1)to measure current? Do I need to enable CV outputs (Hi= 0V) that is shown in the soft front panel?

Or just without enabling outputs I can measure the sink current. The soft panel program does show the current measurements, but I am not sure if SMU can be used like this.




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Accepted by topic author Jetson

Not sure about NI SMUs, as I have not had the chance to use them yet.  SMU's from Agilent could be used this way, so I suppose NI's as well.  You would need to use the SMU outputs in constant voltage source / measure I mode.  You would tell the SMU to hold voltage at 0V, and it would allow current to sink (or source) as required to maintain that 0V at the output.

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Thanks brent2004.

I would think that by outputing 0V, NI cards are really connecting the output to GND.NI soft panel software seems to show current value even when I don't enable output.

But I will follow the 0V constant output way for now.

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Hi Jetson,


The 4130 can be used to measure the current by forcing 0V and setting a current limit above what you are trying to measure on the smallest usable range. The connections from your diagram are also correct. This has the benefit of minimizing the burden voltage that you would typically see if you used a shunt resistor in series with the supply. 


When the 4130 is set to output disabled, the hardware configuration is a 0V voltage limit with a 20mA current limit on the 20mA range. In the disabled mode you should still be able to make the measurement you want to make as the 4130 will still sink current, however the range is not optimized to measure on the order of 5uA. 

Steve B

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