Well, i’m getting the same thing when doing the analysis on the computer. Excel croaks past 1M lines, but the interface for the usb scope i blew up accepts the output from my new scope. It’s reasonably fast at processing it all too. 6M samples was enough data without taking 20 minutes to write to thumb drive, but after applying a low pass filter, the results are still total mush.
Low pass filtering just isn’t the way. All the detail is gone (stands to reason peter, duh).
The switching is clearly visible, and the underlying sine is there too. It’s the right frequency (i was running at 12000erpm so 200 electric revs/sec = 5ms period. There has to be a smarter filter to apply, or some other method. Perhaps not trying to see the sine wave but more looking for the noise or deviation from a perfect sine of the same frequency?
I’m measuring one phase relative to ground. Don’t think there is any other way to do it differently.
Not sure what the right way is. Also, i’ve gotten sidetracked. Seeing the waveform is interesting, and i don’t like to back down from a challenge/failure, but having the knowledge that for whatever reason efficiency is highest at 20khz (vesc 6) is the thing i came for. I’ve got a few more motors to test on the dyno. I’ll give the waveform question some thought. If someone has some good ideas, i’d like to know. I can do some more testing as suggestions pop up. if anyone wants the raw capture data (120mb csv file), lemme know. I’ll ask the grey-beards i know too.
One day i’ll figure it all out.