"Android Programmer" asks:

Hi.
I want to use a car's temperature gauge and sender in order to measure
the temperature of the water going through an installation at home.
The reason is that if it works, this setup would be cheaper than
anything else given the high costs of shipping to where I leave .
The distance of the gauge from the sender will be 30 ft give or take.
This would distort the indication of the gauge given that the gauge
measures the resistance of the circuit between the sender , the wires
and the gauge.

How can I calculate the AWG of the wires that I should use for this
setup ?

The current involved is only about 3ma. Assumming that the voltages
involved are a few volts, and that you want to keep voltage drops to
under 0.1V, max allowable R = V/I = 0.1V/0.003A = 33 ohms.
Just about any wire is going to be waaaaaaay less than that.

My recommendation: Use a 50' 3-conductor AWG 16 outdoor
extension cord, the kind with the tough orange outer clading and
3-prong rubber connectors on the ends. Chop connectors off,
strip ends, and connect to equipment. Available at hardware
stores from Oklahoma City, USA to Nairobi, Kenya, to Perth,
Australia. In a word, "ubiquitous". Price: $10 to $20.

Failing that, use any scrap wire around AWG 16 that you can
get your hands on.

Either way, do watch the connections. High-resistance joints
will screw-up your temp readings far more than wire losses.

--
Cheers,
Robbie Hatley
lonewolf [at] well [dot] com