Patent ID: 6842716

Claim:
Apparatus for measuring the propagation time (T p ) of an ultrasound signal, the apparatus comprising: means for forming an excitation signal; an emitter transducer ( 1 , 2 ) connected to said means for forming an excitation signal; a receiver transducer ( 2 , 1 ) to transform the ultrasound signal into a receive signal; and comparator means connected to said receiver transducer to compare the amplitude of the receive signal with a trigger threshold voltage and to generate a signal representative of oscillations of said receive signal; the apparatus being characterized in that it further comprises: means for measuring a fixed time (HB 1 , HB 2 ) connected to said means for forming an excitation signal in order to measure a fixed time (T 0 ) from the instant at which the emitter transducer is excited; means for determining an i th oscillation (HB 3 , HB 4 ), which means are connected to said comparator means, to count the number of oscillations in the receive signal and to detect the i th oscillation; and means (HB 5 ) for measuring a variable time (T IEX ) between the end of measuring the fixed time (T 0 ) and detecting the i th oscillation.