JPS611693B

PURPOSE:To obtain the city-water meter employable for a long period by providing in a water pipe blade wheels having magnets at the tips of rotary shafts thereof, by transducing rotation of the magnets into electromotive force by a power generating element and by charging a battery therewith. CONSTITUTION:In the water pipe 11a are arranged the blade wheel 12 for counting which has the magnet 13 at the rotary shaft 12a thereof and the blade wheel 15 for power generation which has the magnet 16 at the rotary shaft 15a thereof. When water flows through the pipe, the blade wheel 12 is rotated, the change of a magnetic field by the rotation of the magnet 13 is transduced electrically, and the quantity of water consumed is counted by an electronic circuit 14 and indicated. Simultaneously, the blade wheel 15 is also rotated, the rotation of the magnet 16 is transduced into electromotive force by the power generating element having an iron core 17a and a coil 17b, a quantity of electricity is accumulated in a capacitor 19 through the intermediary of a rectifying element 18, and the battery 21 which supplies power to the electronic circuit 14 and is capable of being charged and discharged through the intermediary of a charging element 20. By this constitution, long-term employment of the battery becomes possible.