bobmcree wrote:... alternately, if you have a good ammeter you want to use for transfer of calibration, compare the cycle analyst readings with those it provides, and scale the default shunt value of .001 ohms by the reciprocal of the ratio you measure to correct the readings.
Thanks Bob. That sounds good. But won't modifying the shunt with solder or whatever make it nonlinear? Or will calibrating to the middle of the range be good enough?
it is just a resistor so there is not a problem with linearity. there is the issue of temperature coefficient, but even if you just use copper wire in parallel with the existing shunt the tc of copper wire is about 400 ppm per degree C so if the wire varies in temperature from freezing to boiling water that is still only a few percent error, and it is only part of the shunt so the error due to temperature is not really a problem.
i keep meaining to fill in the couple of gaps in the schematic, and try to figure out a way to use the error amp in the KA3525 to implement a true current feedback throttle. it should be possible with just a few hacks to the pcb and maybe an added op amp.
i am getting continuing requests to bump up the current limit on the controllers i am refitting with the 4110 fets, since they seem to handle 80A or more quite reliably. i will be doing a couple this week set for as close to 100A as i can get, and will post the details. of course anything over 50A I will not warranty except not to be DOA
I do not approve of this group any longer and regret what it has become. I could once share ideas here freely that is no longer possible.