Abstract: Embodiments cause interaction of an ultra-wide band signal with a substance over a broad range of frequencies simultaneously to obtain a response signal whose distortion is indicative of a composition of the substance.

Abstract: A novel microwave sensor (10, 60, 70, 90, 200, 250, 280) provides low-cost, robust measurement of the electrical properties of fluid substances. The sensor is suitable for use in an industrial vessel or pipe and employs parallel electrical transmission paths (12,14) that differ in electrical or physical length. The electrical length of each transmission path, which may be a two-way path caused by placing a reflective element in each path, is further determined by the electrical properties of the material under test. The frequency (f) of the signal being applied to the sensor is varied in a known manner such that the difference in the electrical lengths (&Dgr;L) of the transmission paths (12, 14) is caused to correspond to an odd integral multiple of a half wavelength. When the frequency is so adjusted and the signals that have traversed the transmission paths are allowed to coherently interfere with one another, then a minimum resultant signal or null is obtained.