Electric gauges and voltage drop

[_Madman_]

Hi!

I am about to connect all of the gauges I've purchased to my car, but I've stumbled upon one question I'm not realy sure about.

The question is how voltage drop affects electric gauges?

I know that there is a huge difference for things like fuel pump, but what happens with low power devices? I am about to feed them from radio connector, so the voltage might be around 12 there, not 14 as right near the battery. Moreover wires to oil press/temp senders are going to be looong...

Can anyone with a good understanding of electronics explain how it will affect precision?

 

[steve]

You have to understand the issue with voltage drop is how much current the thing at the end of the wire uses. If your not using any current then there will be little to no voltage drop.

Fuel pumps draw a lot of current and need thick wires with little resistance to avoid having the voltage drop at the pump. The light bulbs might be the biggest current draw in a mechanical gauge. In electrical gauges the designer has to regulate the incoming voltage for the electronics so as long as the voltage stays within the min and max it will work.

Remember that in a good car the voltage is can range from 9-10volts during starting to 15v during heavy charging.

The signals being measured by the gauge are very low current and reasonable voltage levels so the typical wires provided don't create any sigificant drop due to the resistance of the wire. The only exceptions off hand are things like the knock, O2 and some thermocouples for EGT gauges that have low voltage levels or high source impedance.