Doing sophisticated electronic stuff to a stovebolt engine is an exercise in futility, sort of like putting lipstick on a pig. Trying to measure exhaust O2 concentration with a multimeter- - - - -that's downright ludicrous since one of the diagnostic procedures scan tools monitor is how many times PER SECOND the sensor flip-flops across the median voltage, and if it slows down much, the sensor is deemed "lazy" and needs to be replaced. I hope the meter-reader has extraordinarily fast reading comprehension as the digital meter toggles through a bunch of gibberish numbers. Early automotive computer systems operated on a clock frequency (rate of information sampling) of 10 HZ. Newer ones upped the rate to 90 HZ. Good luck getting any useful info with a meter! LOL!
Jerry
