Abstract: A capacitance detecting proximity sensor forms a proximity detection range in a spatially open region, avoids the effects resulting from peripheral objects outside the detection target, and enables proximity detection with few malfunctions. The proximity sensor includes: a first detection electrode and a second detection electrode that are disposed to have a predetermined range difference h with respect to a detection direction Y in which a detection subject comes into proximity to the proximity sensor and are independent from a ground potential; and a proximity detection circuit that outputs, as a proximity detection output, the difference between a capacitance to ground Ca formed by the first detection electrode and a capacitance to ground Cb formed by the second detection electrode.

Abstract: A water leakage detecting apparatus is capable of detecting water leakage of a water pipe precisely and at low cost. The water leakage monitoring apparatus includes vibration/electric converter for converting an acoustic vibration transmitted to a water pipe into an electrical signal. A signal discriminator processes an output signal of the vibration/electric converter to detect a signal of a predetermined band being held below a predetermined level continuously beyond a continuing condition to generate a sound interruption detection signal. A counter counts the number of occurrences of the sound interruption detection signal.