The rainwater collected by the water-receiving port passes through the upper tube (funnel) and is injected into the metering tipping bucket-the tipping bucket is injection molded of engineering plastics and divided into two half-cone chambers of equal volume with a middle partition. It is a mechanical bistable structure. When one chamber receives water, the other chamber is in a waiting state. When the volume of the received rainwater reaches a predetermined value of 0.5mm, it will overturn due to gravity and be in a waiting state, and the other chamber is in a water receiving state.