fuel tank sender wiring

little bit of help needed on top the sender which is the float on a wire sort there are two terminals one on a nylon block and one on the casing, does any body know which one is the earth,
TIA Steve

 

http://www.midsouthvw.com/TechTips/tech_tip_FuelGauge.htm

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The one on the casing ,the other one is to the resistor winding , on the float arm.

 

lovely job thank you for your help, its along time since I have been on the forum, back in love with my camper again,