Air Craft Fuel Gauge Project

Thread Starter


Joined Dec 3, 2009

I am working on a fuel gauge for my 77' CJ7 jeep. the gauge came from a B17 air craft bomber. I was told I need to create a circuit with a digital pot.

My fuel tank reads about 17Ω full and about 80Ω empty, the B17 gauge reads empty with no power/resistance and 128KΩ full. also with 12.44v DC , current is 140mA with no resistance (pegs out). can someone help with a basic circuit using A digital pot to make the fuel tank levels match the B17 gauge?

Thanks :)


Joined Oct 2, 2009
I fail to see what a digital pot brings to this problem?

You have not gathered enough info to design a suitable circuit.

It is unlikely that even if you match the sender and the gauge at the two endpoints (i.e. Empty and Full), that the resulting gauge indication would be linear (or very accurate).

Lack of linearity is mostly caused by:

Mechanical stops on the sender float arm (to keep the float from rubbing on the top or bottom of the tank).

The geometry of the float arm as it causes the wiper to traverse the rehostat.

The linearity of the rehostat progressive winding.

The non-linearity caused by putting a fixed resistor in series with the sender in order to create a voltage divider to produce a voltage proportional to wiper position.

Without testing it, there is no basis to know if the gauge reading is proportional to input voltage, input current, or the resistance tied between the input to ground, or input to + supply?