Non linearity of current and voltage

Question

Closed this issue 3 years ago · 6 comments

When looking at the calibration, there is a non linearity observable, which effects both current and voltage.

Answer 1 · 2022-03-08T05:32:21.000Z

The current measured by the Multimeter and the DAC setting have a quite linear dependence.

Answer 2 · 2022-03-08T05:38:05.000Z

This behaviour might be caused by the 3V3 Zener diodes, which limit the voltage to the ADC inputs.

Answer 3 · 2022-03-08T09:10:10.000Z

together with the 1k current protection resistor, this might cause the observed behaviour.

Answer 4 · 2022-03-08T09:44:47.000Z

By using a simulation, it is possible to reconstruct this issue.

Answer 5 · 2022-03-08T18:30:12.000Z

By removing the Zener Diode and replacing R27,R28,R39,R40 with 56k, the result looks quite linear.

Answer 6 · 2022-03-09T05:12:09.000Z

Also with more points, the behaviour stays linear.

But, on the other hand, if no load or a very high ohmic load is connected, this might damage the controller.