Quote:
Originally Posted by ghlkal
Just to follow up now that I can read the RPM from the HVAC display. Here's how far off my tach is:
tach reads / actual RPM
1000 / 650
3000 / 1750
4000 / 2325
4500 / 2700
5000 / 2975
6000 / 3500
This is up to a 70% error  |
Well, it sounds like waaaay more than the run of the mill drift of resistor values in the voltage divider: a connection on the board, or (I hope not) the dual op amp chip.
I'd try the cal approach first and see where we are after that.
P.