Abstract: A method and apparatus for detecting a fluid; said method comprising providing one or more oscillators transmitting electromagnetic energy; providing one or more resonant circuits receiving electromagnetic energy from the oscillators; bringing the fluid and the one or more resonant circuits into contact with each other so that the receptions of electromagnetic energy of the resonant circuits are changed; and detecting changes of the transmissions of the oscillators by changes in one or more characteristics thereof upon the changes in the receptions of the electromagnetic energy of the resonant circuits; and use thereof for the detection of fluid levels, empty containers, and leak of fluids from containers and bodies containing said fluids; e.g. for monitoring collection of drain fluid from a human or for monitoring leak of fluid from a human suffering from urinary and/or fecal incontinence.