s close enough, the switch closes and the reed is pulled to the closed position. The magnet is positioned on a dial (in some cases a turntable) that rotates due to the flow of water.When the magnet travels far enough away, the reed is released and the switch opens. one time of switch on and off makes a single "pulse." by caculating the amount of pulse it comes to the water flow rate usedUltrasonic water meter: It is a new type of water meter, which detects the time difference caused by the chang