A liquid gas level measuring system for use in a liquid gas tank and designed to cooperate with a float level gauge head mounted on the liquid gas tank and made of magnetically inert material, the system comprising: a dial module attachable to the float level gauge head and comprising: a dial module body having its bottom face shaped so as to be mounted in the level gauge head, an indicating rotary element arranged in the dial module body and serving for visual indication of liquid gas level in the tank, at least one dial magnet arranged below the indicating rotary element, whereby said at least one dial magnet and the indicating rotary element are arranged such that during rotation about the common vertical rotation axis the rotation angle of said at least one dial magnet corresponds to the rotation angle of the indicating rotary element, a tank volume scale circular in shape and adjusted to cooperate with the indicating rotary element so as to indicate percentage of the tank volume occupied by the liquid gas, and a dial module lid provided on its top face with at least one connection element, whereby at least part of the dial module lid peripheral area is made of a transparent material, and a sensor module releasably connected to the dial module and comprising: a housing provided with at least one connection element corresponding to the at least one connection element of the dial module lid and adapted to form a releasable connection with the fat least one connection element of the dial module lid, an electronic module comprising a Hall effect sensor and a radio module, a battery connected to the electronic module, an antenna connected to the radio module characterised in that the dial module comprises also a cylindrical guide magnet arranged above the indicating rotary element and cooperating with said at least one dial magnet, whereby said at least one dial magnet, the indicating rotary element and the cylindrical guide magnet are arranged such that during rotation about the common vertical rotation axis the rotation angle of said at least one dial magnet corresponds to the rotation angle of both the indicating rotary element and the cylindrical guide magnet. a dial module attachable to the float level gauge head and comprising: a dial module body having its bottom face shaped so as to be mounted in the level gauge head, an indicating rotary element arranged in the dial module body and serving for visual indication of liquid gas level in the tank, at least one dial magnet arranged below the indicating rotary element, whereby said at least one a dial module body having its bottom face shaped so as to be mounted in the level gauge head, an indicating rotary element arranged in the dial module body and serving for visual indication of liquid gas level in the tank, at least one dial magnet arranged below the indicating rotary element, whereby said at least one dial magnet and the indicating rotary element are arranged such that during rotation about the common vertical rotation axis the rotation angle of said at least one dial magnet corresponds to the rotation angle of the indicating rotary element, a tank volume scale circular in shape and adjusted to cooperate with the indicating rotary element so as to indicate percentage of the tank volume occupied by the liquid gas, and a dial module lid provided on its top face with at least one connection element, whereby at least part of the dial module lid peripheral area is made of a transparent material, and a sensor module releasably connected to the dial module and comprising: a housing provided with at least one connection element corresponding to the at least one connection element of the dial module lid and adapted to form a releasable connection with the fat least one connection element of the dial module lid, an electronic module comprising a Hall effect sensor and a radio module, a battery connected to the electronic module, an antenna connected to the radio module