Exactly how do you install a voltmeter?

 

Since you didn't get any replies and left such a vague title as the topic. I'm going to throw my simple question(s) in the mix and give you a BUMP!

What purpose does a volt meter gauge serve? What are you reading on the gauge? I am guessing the voltage in the battery. Does it fluxuate (sp? that just doesn't look right ) as the car is running or something? I would guess that the gauge would just let you know when the battery is about dead and needs replacing.

I'm looking to get a 3rd gauge which is why I ask

1) Oil pressure
2) Water temperature
3) ?????????

Most likely going to get all Autometer Phantom series Electrical gauges

PS <> How hard is this gauge to install in a 93 Cx Hybrid (98 GSRusdm motor)