Differential impedance with analog discovery 2 using API Python ?

[tanguyvr]

Hello,

We are trying to perform differential impedance measurment with the Analog Discovery 2. It works directly from the interface but we didn't find how to select, in the API, the topology for the differential impedance (W1-C1P-DUT-C1N-C2-R-GND). We can only select two topology (0, 1 and 8).  Could you help us ? If possible, do you have a code example showing how to work with this differential impedance ? Thanks !

[attila]

Hi @tanguyvr

The Mode 2 is for differential W1-C1P-DUT-C1N-C2-R-GND mode.
dwf.FDwfAnalogImpedanceModeSet(hdwf, c_int(2))

I think I have left out from the manual because I don't wanted to recommend using it. In this mode two scope probe are connected between DUT/R which could alter the measurement specially at high frequency and impedance.

[tanguyvr]

Dear Attila, thanks for your quick reply. I understand why. So, if we want to do differential measurment, is it better to perform two measures at using a 2 electrodes set-up and substract the results ? Regards, Tanguy

[attila]

Hi @tanguyvr

The impedance measurements returned are for the DUT with respect to the selected mode and reference resistor.
The calculations are performed in the function, there is no need to perform additional math.

The results of mode 0 and 2 are similar in the range where DUT and R are comparable.