Â­TÂ­here are many different ways to create a motion sensor. For example: 1  It is common for stores to have a beam of light crossing the room near the door, and a photosensor on the other side of the Â­room. 2  When a customer breaks the beam, the photosensor detects the change in the amount of light and rings a bell.
Definition of weir. 1  1 : a fence or enclosure set in a waterway for taking fish. 2  2 : a dam in a stream or river to raise the water level or divert its flow.
effluent, sewer water. 1  waste, waste material, waste matter, waste product - any materials unused and rejected as worthless or unwanted; they collect the waste once a week; much of the waste material is carried off in the sewers. 2  sewage, sewerage - waste matter carried away in sewers or drains.