PURPOSE: To measure water level continuously and accurately by determining the pipe length above the water surface based on the sound in the pipe picked up through a microphone.
CONSTITUTION: Sound in a pipe 2 is picked up through a microphone 1 and delivered to an input unit 5 at a data processing section 4. Data is delivered with very short duration from the input unit 5 through two Fourier transform units 6, 6 to a surpass period interval operating unit 7 where a surpass period interval 4t is operated and fed to a pipe length operating unit 8. The pipe length operating unit 8 determines a pipe length l from the interval Δt and a sound speed (v) according to a formula l=Δt.v/2. A water level operating unit 9 determines a water level based on the pipe length l thus operated and produces information or alarm as required.
TOMITA KENJI
TAKIZAWA TARO
SAIDA ATSUSHI
