Car Fuel and Temp Meter

[VictorPS]

Hi,

I try to understand how the meter in my car Dashboard Fuel and Temp guage,
open up, I see a meter with 3 input.

I have no idea what this kind of meter is, can anybody tell me what is it and how it work?

Thank you,

 

[Hero999]

It's a moving coil meter.
https://en.wikipedia.org/wiki/Moving_coil_meter

One wire goes to 0V and the other wires go to the respective meter.

 

[VictorPS]

I still don't get it, an Analog meter (moving coil meter ) have 2 lead only, but this have 3 lead... and is it because of this, the pointer of meter will be very stable, not moving out much even a vibration shock during car drive, am I right? Where can I get more info about this kind of meter?

 

[Hero999]

There are two meters on the panel, one for oil temperature and another for fuel level.

 

[ronsimpson]

In my old truck there are two answers for why three “inputs”.
1. Some of the meters have three leads but only 2 are used.
2. Two of the meters have leads labeled “gnd”, “+” and “S”. The meter needs power and ground to work and one wire that goes to the sender. If you look at the Moving_coil_meter link they show a magnet. It could be made with a electro-magnet that requires power.

 

[VictorPS]

thanks for reply, I have open up the meter, I notice it is moving magnet, the coil with 3 lead is fix unmoveable.

And yes, there is (+) and (Gnd) connect to two lead of the coil through resistor.
But to control the meter, what shall I input to (S)? a resistor to ground or a small voltage input?

Here I attached more photo for better understanding.
Thank you,

 

[Hero999]

It's the same as the article on Wikipedia except that it uses another coil instead of a permanent magnet.

If each meter has three leads (which is what I think you're saying), then the third lead is for the outer stationary coil.