WATER_LEAK_ISOLATOR

Published:2009/7/7 21:10:00 Author:May | From:SeekIC

Master indicator monitors large number of two-electrode waterleak detectors simultaneously, with each detector indicating presence of water by producing unique tone signal. Only two wires are needed between detectors and master indicator unit.Each detector location has quad NOR gate. First gate is water sensor, second is inverter, and last two form astable MVBR. When sensing electrodes are dry, resistance between them is above 500K and MVBR is disabled. When water drops resistance below 100K, MVBR oscillates at audio frequency determined by its RC time constant, equal to 1/1.4RC where R is in ohms and C is in farads. CP value in farads should be 1/1000 of lowest frequency used by detectors. L in henrys is about 1/600 of lowest frequency.-F. E. Hinkle, Multiplexed Detectors lsolate Water Leaks, Electronics, Dec. 11, 197S, p 116-117.



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