I was wondering what type of sensor would work with my g540 drive. I am confused on how to hook one up because the g540 seems to call for the signal to be connected to ground for the input to work. I can't imagine a reed switch could respond to 20K rpms or more. I would assume some sort of optical pick-up, but those have a output of 5volts or more. The g540 is somewhat popular, so i am guessing there is someone who has a spindle speed setup that works. Please help if you can. Thank you.