VDO 12 Volt Cockpit Vision Fuel Gauge Float Arm (Screw Ring] 52 mm diameter.
The fuel reserve indicator applies the resistance measurement principle. A sensor (lever-type) in the liquid reserve to a corresponding resistance value. A turning magnet ratio measuring movement measures the resistance value. It comprises three stationary coils wound at 90 against each other, and a rotating permanent magnet disk in these coils.
The coils are connected to determine a ratio, so that the instrument is intensitive to on-board voltage fluctuations.
This means that the pointer travel is only determined by the magnitude of the current flowing through the measuring system. The pointer movement must be dampened when the liquid level is measured by a lever type sensor; in this case the coil body is filled with dampening oil, the rotating magnet moves in this oil to obtain dampened pointer movements. A magnetic shield prevents effects of external magnetic fields, indication errors due to temperature changes are corrected by a compensating resistor. A dropping resistor is used to adapt the measuring movement to higher operating voltages (e.g. 24V).