Measurement errors?

[Sinaptec]

Hello,

I am currently using the Analog Discovery 2 with the following set-up (Two first pictures).

The two resistors used here are both 10 kOhm resistors.

Using the "W1-C1-DUT-C2-R-GND" mode, I obtain the following curves third picture). As you can see, when the frequency increases, the phase becomes negative.

Using the W1-C1-R-C2-DUT-GND, I obtain the following curves (fourth picture). The set-up has been unchanged but the phase now increases with the frequency.

This can be summarized with the following picture. (fifth picture)

Is that normal? Isn't the phase curve supposed to be the same in both cases?

 

Another question I get concerns the Analog Discovery Impedance Analyzer. The datasheet says that a warning is shown when the ratio between the two resistances exceeds 25%. However, as you can see (6th picture), I only get the warning when this ratio is around 96,5%.

Is that normal?

 

Best Regards

Edited July 6, 2022 by Sinaptec
Typo

[attila]

Hi @Sinaptec

The warning threshold is set to Vrms/Irms/R exceeding 25x or x/25 (1-x/25=96%), indicating low measurement precision than can be improved with lower or higher reference resistor.

Edited July 6, 2022 by attila

[Sinaptec]

Thank you for your quick answer.

Do you have any idea about the phase different sign when we switch from the "W1-C1-DUT-C2-R-GND" mode to the "W1-C1-R-C2-DUT-GND" mode?

[attila]

Hi @Sinaptec

Looking at the code, the input phase always shows C1 - C2 phase, it is not modified based on mode/order.

Edit: The Input Gain and Phase are raw values, may be useful for network analysis. All the other measurements take in consideration the probe/scope input impedance and open/short compensations when these are performed and enabled.

Edited July 6, 2022 by attila

[Sinaptec]

Hi @attila

Thank you for your answer.