If the alternator is only putting out 12 volts then it is defective and needs replacing. It should output from 13.5 to 15.5 volts DC. You will need a digital volt meter to get an accurate reading. Analog volt meter is not accurate enough.
Volts
A device that measures volts.
A volt meter or a multimeter on the voltage scale.
12.6 volts as read with a digital DC volt meter.
It is a 12 volt battery. Fully charged it will read 12.6 volts with a digital volt meter.
A fully charged 12 volt battery will output 12.6 volts are read with a digital volt meter.
14 volts
If this is a consumption meter with 120/240 volts, the answer is yes.
All voltage reading are usually read with a volt meter. This volt meter can be a hand held unit like electricians use.
With a voltmeter Keep volt meter terminal on phase and neutral wire and it will show the exact volatage
Fully charged it should read 12.6 volts with a digital volt meter. 12.4 = 75% charge, 12.2 = 50%, 12.0 = 25%.