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Any ideas what the middle three contacts are? (12v Battery Voltimeter)

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JimB

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Gnd is ground, the 0 volt reference point in the circuit.

Vcc is the positive supply voltage for the circuit, probably 5 volts.

T, no idea.

Looking at the label on the side of the module, there are tick boxes for two types of module.
Maybe there is a connector fitted here on the other variant of the module.

JimB
 

tcmtech

Banned
Most Helpful Member
It might relate to being a lower voltage Tap point for accesing it's own internal 5-volt rail that powers the driver IC's on the board.

I've found many small digital meters that have wide input range ratings to have taps like that to bypass the voltage regulators if an external 5-volt source is to be used if they are designed to sense the same voltage source they are powered from and that supply voltage goes below the minimum forward drop voltage of their onboard voltage regulator.

I've used that cheat a few times in applications with cheapo digital meters to make them work properly in other applications where they couldn't be powered off the same source they were reading from like they had been designed to do.
 

schmitt trigger

Well-Known Member
It might relate to being a lower voltage Tap point for accesing it's own internal 5-volt rail that powers the driver IC's on the board.
.
This is a very feasible assumption.
The assumption can be easily be verified, by applying voltage to the unit via its red and black wires, and then with an external DMM measure the voltage from Gnd to Vcc and T respectively.
 

Ramussons

Active Member
The device is powered by Vcc-Gnd.
The measurement is T-Gnd.

This permits measuring a higher voltage the Vcc by using a Voltage Divider to feed T
 
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