I'm installing a VDO tachometer, a baisc one without an hour meter. I've got it all wired up, but there is something in the instructions about manually fine tuning it:

"Before your VDO Tachometer will function properly with your engine, you will need to configure it as shown in Diagram C (see below). the table at the top shows how to set the DIP switches for use with an ignition coil; the table at the bottom shows how to set the DIP switches when using the tachometer with an alternator. Note that manual fine tuning can be done using the potentiometer on the rear of the instrument. (See Diagram A). NOTE: This procedure should be done by an experienced mechanic ONLY, using a hand held reference tachometer. Fine calibration can be made between 30% and 100% using this fixed reference."

Can anyone explain what this means, and how it is done? Or is it even necessary? I don't care if it's slightly inaccurate. I won't be racing my truck or anything.

Thanks!

1940 Chevy 1/2 ton, 12 volt, 350/350th