@DougS :
Even fuel floats from the 70's are "digital" in a way, its a passive resistance meter based on a negative voltage feed. They typically die not because of mechanical failure but because the cables to and from corrode sufficiently to toss the reading out the window. In the case of a camaro I once knew it went off when the rust levels on the crossmember the tank was strapped to consumed better than 30% of the steel.