Tach Question

["Jen/Scott" <jsloan798@earthlink.net>]

I have a question concering my tach. I installed an aftermarket tach
becuase my original tach seem to bo inaccurate. After I installed it,
and looked at the readings, it seems as though the original tach read
twice as high as the new one. The only thing I could think of is that
because my car had dual points, maybe it just reads that, making it
twice as high? Does this sound right? If so, what can I do to get the
stock one correct? Thanks
 
Scott