Buster,
The automatics side of things is all done by computers. The fuel quantity indication system is the system that provdes the aircraft with information on the volume, mass, and temperature of the fuel (aircraft meaning the refuelling panels and the cockpit). On the 320 its a Fuel Quantity Indicator Computer, A330/340 Fuel Control & Management Computer which in Boeing speak is like the Fuel Quantity Processor Unit on the 777.
The fuel level, temperatre, and density is measured by capacitance probes, and a cadensicon (densitometer + permittivity compensator) sensor. The probes give the computer level and temperature, and the sensor lets the computer determine the fuel mass. If the sensor fails a capacitance index compensator kicks in which gives the dielectric constant of the fuel, which is the backup to compute the fuel mass (not as accurate).
Manual mode - just like a Metro, the fuel quantity can be manually checked by using the magnetic level indicators.
Z