I recently undertook calibrating the capacitance fuel tanks and 4500 fuel gauges. Ran into a brick wall concerning the sending units and calibrating the tanks. Thanks to Todd at Princeton Electronics, he "broke the code" on the problem.

When I received the sending units from Advanced Flight Systems last year, one was a single set point and one was a two set point for Van's capacitance plates. The voltage is different. The right tank was fairly simple, but the left tank wasn't, which included draining the tank and starting again.

After it was all over I noticed that on the back of the sending unit was a label. One had 1sp on the label and the other had 2sp. Last year I wouldn't have known what that meant. Today I do. Do your own quality control.