[AXMonster]

I know that Ford tend to use segmented senders as part of the fuel delivery module that have something like 50 segments to read from the top of the tank to *near* the bottom. The readout is dependant on which segments the float places the sender (as there are I believe 2 or 3 contacts on the wiper arm that sends the signal), so the output is an average voltage across the segments. It also works on a voltage, not resistance input. The instrument cluster control module then interprets this voltage and applies logic filtering to damp out changes in level when cornering (slow fill constant). If the ignition is turned off and then on again and it sees a different tank level between off and on, it then applies a fast fill constant and the guage goes directly to the new reading (as it determines that the tank has been filled up).

New systems are pretty complex!!