# Digital Multimeters (DMMs) and Precision DC Sources

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## Using PXI 4110 as precision DC current source and Measure Unit (SMU) )

Hi,

I want to use PXI 4110 as precision DC current souce and measure unit.Can it be used as SMU? I am using channel 2 (2mA to 11mA, Range :20cmA). Sourcing a current sweep of 2 - 11 mA with a step size of 1 mA through a resistor of 173 ohm, the readback voltage and readback current (readback current * 173) are not same.  I want to know its reason.

Regards,

Khan97

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## Re: Using PXI 4110 as precision DC current source and Measure Unit (SMU) )

Hi Khan83

The PXI-4110 can be used to source current in the range you described. When taking the current measurement, does it vary from sweep to sweep? For example, at 6 mA the readback voltage is 1 V the first sweep and .8 the second. Also, as we sweep through, is the error seen a linear error? Does the resistor heat up causing a change in the actual resistance?

Regards,

Jason D

Applications Engineer

National Instruments

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## Re: Using PXI 4110 as precision DC current source and Measure Unit (SMU) )

No, the error is not linear, It increases upto 5 - 6 mA and then it again decreases. Resistor 173 ohm is at room temperature.

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## Re: Using PXI 4110 as precision DC current source and Measure Unit (SMU) )

Hey Khan,

Can you post a circuit diagram and a graph of your output data?

-John Sullivan
Problem Solver
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