how to wire 3 car voltmeters to 1 switch

i m going to wire 3 prerady 12v voltmeters to my car one to the battery second to the alternator and the third the distro block before my amps. my question is i want to control all three voltometers by one switch since i thinking i cant put 3 pos leads on one switch and control them i was thinking the grounds is this possible. the 12v meters have three wires one i know is the pos and ground and the other i dont know i havent purchased them yet. i want to make sure this is possible before i buy so i can have the  correct equipment thanks guys.

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1993 sdv
Alpine 4x6 6x9 5 1/4 swr-10d4
alpine v60
12.5 VGA flip down
Nettop pc w/10" touch screen
78nova
5-re audio 5x7 ,10" sub &
Xtx-500.5
"Take the faceplate off get the jumperpack"

If I had to guess, I would guess that the 3rd wire is a switched wire that would turn the meter on.  if that is the case, simply run all 3 of those wires to the switch you intend on using.  Connect the other side of the switch to a 12 volt source.

Ok thanks I changed the plan it was just two 12v voltmeters one to the battery and amp. What kind of switch I need . Am I supposed to look in the voltage area not amps right

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1993 sdv
Alpine 4x6 6x9 5 1/4 swr-10d4
alpine v60
12.5 VGA flip down
Nettop pc w/10" touch screen
78nova
5-re audio 5x7 ,10" sub &
Xtx-500.5
"Take the faceplate off get the jumperpack"

I must have been drinking when I posted that answer.  The thirs wire is probably the illumination wire.  Yes you should be able to interrupt the ground connection to turn the meters off.  Yes you nned a switch to handle the current of both meters and the illumination of both.  I am sure that a 3 amp switch should be ample.

There may be an issue with the meters trying to find ground through the illumination wires.  When you purchase the switch, make sure you get a Double Pole Single Throw switch.  If there is an issue, you can interrupt the illumination wire as well.

Here is the voltometer I'm going to use . I want one on the alternator and one on the battery. If they can be on one switch that could be great. Here's the link below on the pic its three wires. I believe its power ground and the actual testing of the voltage correct me if I'm wrong.
https://cgi./STINGER-SVMB-VOLTMETER-BLUE-3-DIGIT-DIGITAL-DISPLAY-NEW_W0QQitemZ360194054151QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item53dd3d1807#ht_1453wt_943

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1993 sdv
Alpine 4x6 6x9 5 1/4 swr-10d4
alpine v60
12.5 VGA flip down
Nettop pc w/10" touch screen
78nova
5-re audio 5x7 ,10" sub &
Xtx-500.5
"Take the faceplate off get the jumperpack"

The third wire could be a trigger wire to turn the device on.  Get the meters and when you see the instructions, we will go from there.