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.
Learn About Effluent Guidelines. Effluent Guidelines are national wastewater discharge standards that are developed by EPA on an industry-by-industry basis. These are technology-based regulations, and are intended to represent the greatest pollutant reductions that are economically achievable for an industry.