A radiofrequency resonant circuit sensing device of the type comprising folded substrate wherein capacitor plates are mutually displaced to provide a shifted resonance frequency, a method of its production, an apparatus and sensing device comprising it and its use 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 faecal incontinence.
