Using Analog Discovery 2 for resistance measurement

[altarace]

Hello everyone, I'd like to plot resistance (0-100K) overtime on three different points of a system. Is it possible to accomplish with the AD2 ?

Thank you

[JColvin]

Hi @altarace,

Presuming I'm understanding you correctly, plotting resistance over time is not something that the Analog Discovery 2 can do. The only way I can think of to do something like this would be to apply a constant current (with a correspondingly variable voltage) and then use an oscilloscope to get voltage values before and after the DUT and then calculate the corresponding resistance; but the Analog Discovery 2 is not capable of supplying a constant current (as in it lacks the physical components to do this).

You could maybe use the Discovery Power Supply, https://digilent.com/reference/test-and-measurement/discovery-power-supply-3340/start, which can be set up to provide constant current, in conjunction with the Analog Discovery 2, but you would run out of analog inputs before getting to measure the voltage drop across all three points in your system.

It's possible to set up more convoluted systems with more analog inputs to achieve what you are wanting (simultaneous measurement and tracking of impedance of three different points), but I would probably instead recommend looking for a dedicated device that does this instead. (Admittedly though, I'm not readily finding any such devices that track resistance over time from general internet searches).

Thanks,
JColvin

Edit: I blanked on the whole reason why resistance over time isn't something that is done. Because you have to measure the voltage drop over a component that has a known amount of current running through it, you can't have your system be actively running to introduce changes. Otherwise, you'll have extra current and voltage changes that aren't properly accounted for so all of the measurements (individual or over time) will be inaccurate.

If you are expecting changes in resistances in a system, maybe because you are using thermistor, you would need to either look up the datasheet of the individual component, or model and simulate your system to mathematically calculate the amount of current and voltage at a particular point in your system.

Edited May 18, 2023 by JColvin