These systems are installed on existing Rochester-type gauges and usually operate using 2G/3G. Fairly reliable, although not very accurate, they can measure the remaining amount of LPG in %. Measurements vary between 15 and 85%. So when the gauge reads 15% it means the LPG tank is empty. When the gauge reads 85% it means the tank is full.
So these sensors have a real necessity, they must be ATEX certified to avoid any explosion in case of a tank leak or gas release.
Today, it is estimated that in France, out of 760,000 tanks in operation (according to figures from the Butane Propane sector of France Gaz Liquides, the federation of market players), less than 10% are currently equipped with this type of system.
The main tanks equipped with this system are those used for industrial applications. Very few private individuals who heat with propane or in agriculture already have monitoring of their tanks.