Gordo, what do you know about fuel tank gauges

[Lancerbye]

Originally Posted by Stranded Mariner

I read something about that before (Maybe even on this forum). Isn't the principle that the system measures the back pressure on a sounding pipe, which changes with hight of the medium in the tank?
We used to sell industrial systems like that, and they are very reliable.

Yes they are still occasionally used in certain applications especially where it is a pneumatic only measuring and control system. Where electrical equipment is not available or desirable. More high tech measuring equipment has replaced these in most instances but the cost of that equipment and the complexity has kept guys like me employed for a long time. Ultra sonic equipment, Capacitance probes, radar transmitters, inductive probes and load cells have all been used to measure level. Having installed and repaired all these systems is the reason I don't want them on my boat. Simple is good.

[GordMay]

Originally Posted by Stranded Mariner

I have seen those before as well. The tube is basically a capacitor, and the capacity changes with the amount of dielectric medium, in this case fuel or oil. No moving parts, so not much can go wrong with the sensor.

A Capacitance Fuel Gauge Sender either has two Rods, or more usually a Concentric Rod where the inner rod and outer tube form the two plates of a capacitor with little discs inside being the separators for them.
The capacitance changes depending on the depth of the probe’s dive into the fuel, which is dielectric.
With no fuel up inside the "capacitor" it has a given value of capacitance.
As fuel is added to the tank and it goes up inside the tube assembly, the capacitance changes.

CENTROID PRODUCTS - Computerized Tank Display - Electronic Senders - capacitive fuel gauges

NMEA2000 Fuel Tank Level Sender

Panbo: The Marine Electronics Weblog: Offshore Systems 3271, the perfect fuel tank sensor?

[delmag]

i'm happy to report that i just installed a wema sender in my starboard fuel tank today.
it's a veritical rod with a doughnut float that rides up and down on it. not sure how it works....maybe some kind of inductive thing. hopefully i can get the port tank done tomorrow. BTW, they have two different kinds of senders. one is threaded and screws in, which i thought sounded a little iffy. the other has a flange with 5 or 6 holes for fasteners. my tanks are under the cabin sole and don't have any access for a dipstick.

[Chief Engineer]

I think I am going to opt for the WEMA

I can't justify the cost of the Tank Tender Unit.....Maybe if the vessel was 70 feet or longer.