ULTRASOUND GAS-FLOW METER FOR HOUSEHOLD APPLICATION

A novel ultrasonic flow meter for monitoring the gas consumption in households has been developed as an advantageous replacement for the conventional mechanical meter utilized so far. The meter works on the time-of-flight principle, where ultrasound pulses are transmitted across the tube cross section and the difference between upstream and downstream propagation is evaluated. Special features of the tube design are the rectangular shape of the flow channel, the oblique triple-folded transmission path and the parabolical reflector, which selectively enhances the signal-to-noise ratio. Broadband piston-shaped transducers of the radius-to-thickness conversion type have been developed with FEM support. They allow flawless signal transmission even for gases with losses of up to 23 dB compared to air. Error margins of +/-1.5% (maximum flow) to +/-3% (minimum flow) are met within a 1:150 flow range, independent of gas composition and temperature. The power-saving ultrasound technique warrants a ten-year operation time from a single standard Li cell.