So one thing that I noticed in the episode is that the current sense resistors appear to be on the negative rails. So I did a few tests, which I've got here in both video and text form (take your pick):
Text: So I did some tests and:
A. There's a 40 milliohm resistance if you pass current into Ch2– and out of Ch3– (which are, in theory, common/supposedly shorted out), which corresponds exactly to the theory that current has to pass through both 20 milliohm resistors to get from one to the other.
B. However, if you short-circuit Channel 3 and test for a voltage drop across Ch2–/Ch3–, it fails to materialise. If there was a 20 m? resistor between Ch3– and """true ground""" , then you'd expect to be """true ground""", and therefore Ch2–, to be 60mV lower than Ch3– at 3A. Instead, it's 0mV different.
C. Ch2– and Ch3– appear to be identical; it doesn't matter where you sink current that is sourced by Ch2+ or Ch3+, the current measurement is always spot on. So what are those resistors doing!?
I'm tearing my hair out, I can't figure out a circuit schematic that exhibits this combination of behaviours. Probably missing something obvious though!