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unipolar current measurements

Question asked by amf on Nov 19, 2015
Latest reply on Dec 4, 2015 by LiamR

I'd like to try the same unipolar DC current measurement you mentioned that you ran to get measurements of very small currents.  That is, I'd like to set up a 4-wire measurement for 0 uA to 1 uA.  I'd apply a step voltage of 600 mV and I would set R_TIA to make the max voltage at the output of the TIA be 750 mV (or would it be twice 750 mV for a unipolar setup)?

 

Is there any app note on this unipolar current measurement aside from the attached two files?  I had trouble following the discussion in the .pptx file because on Slide 2 it mentions that the assumption in the ADI example is that they have a 0 uA to 20 uA current into the TIA ... yet all the following slides show 0 uA to 40 uA.

 

I looked through the code in the SDK 2.3.0 example in the UnipolarCurrentMeasurement workspace, but I think it's set up for a 2-wire measurement?  What would I need to change to be able to use it for a 4-wire measurement?

 

Would I set R_TIA as:

       R_TIA = 0.75V/1uA 

 

or

 

      R_TIA = (2)(0.75V)/1uA

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