A method of detecting an effluent level in an aircraft lavatory holding tank and a device for practicing the method. The device uses electrodynamic forces of different values generated by an electro-impulse solenoid to determine whether a detector is contaminated, to dislodge contaminants, and to measure...http://www.google.fr/patents/US5035140?utm_source=gb-gplus-shareBrevet US5035140 - Self cleaning liquid level detector
