Float Fuel Sensor w/ Flop Tubes

[DaX]

No, this isn't a question of whether or not this is a good idea - it's already done.

I mounted my sensor on the baffle of the tank in the second bay. I'm getting ready to attach the leading edge and start attaching main skins. I want to put the tank on before I do this. Doing so will mean I won't have access to the sensor, so I guess I need to go ahead and stub out wires to the wing root. When testing the sensor, I used a multimeter on the screw, and on the body of the sensor. The sensor is on the baffle with no gasket - only proseal.

My question is this:

To stub out wires, I understand that one wire needs to be attached to the screw, but where does the other wire attach? Do I need to:

1) Remove one of the attaching screws and put a wire underneath that?
2) Solder a wire to the back of the sensor?
3) Attach the wire somewhere else?

I really don't want to do option 1, but will if I have to.

I wasn't sure if the ground from the sensor could be attached elsewhere, since the sensor is possibly isolated from the rest of the tank with proseal.

Thanks for any and all help!

[Lycosaurus]

Originally Posted by DaX

To stub out wires, I understand that one wire needs to be attached to the screw, but where does the other wire attach?

Measure with an Ohm-meter that the sensor plate is grounded to the tank (hopefully via the screws, since the proseal will act as a pretty good insulator). If you have continuity, then you can attach your ground reference wire anywhere else on the airframe or tank.

Make sure you allow yourself a good extra length of wire so that you don't end up ripping it out if/when you remove the tank at a future date.

[DaX]

OK, maybe I should have addressed this to everyone with float type sensors - where is everyone picking up the sensor ground at?

[DaX]

From the horse's mouth:

Matt,

You would think that the sensor is isolated from the airframe by the tank
sealant, but it probably is not. The screws usually wipe enough sealant from
the plate nuts to make a good ground. Test it again and this time attach
the ground wire to the wing skin or tank skin. If it tests OK, then a second
wire is not necessary. If you do need a second wire, under a screw head is
a good place.

Bruce Reynolds
brucer@vansaircraft.com

...not implying that Bruce is a horse.