[olddog]

Theoretically you can filter noise out with a capacitor and a resistor. It is done all the time in other applications. The down side to a filter is that is slows down response time. In this case you do not need a fast response. With the gas sloshing around, you will never get an accurate reading until the sloshing stops, but I think you could improve the reading quite a bit.

The sending unit is a variable resistor. If I remember correctly the + voltage goes to the gauge. The other side of the gauge goes to the sender, and the other side of the sender goes to ground. I'm thinking it would be best to put the capacitor across the gauge, with a resistor in parallel. The bigger the capacitor the longer it will take it to charge up. The higher the resistor ohm the slower it will discharge the capacitor. This will slow down the changes in the gauge, as the voltage across the gauge will be more stable.

I can talk to my I&E guy and see what sizes he would try first.