Spindle Tach

[Bustednuklz]

I was wondering if anybody out there knows of a tach set up that I could use on a Grizzly G8689 mini mill. I would like to have a general idea of my spindle RPM. I know what the manufacturer says the ranges are between for both high and low gears, but the adjusting knob seems to be a bit 'touchy' in a couple of areas. Really don't think that it is bad enough to replace.

Thanks in advance
Steve