Patent ID: 7159472

Claim:
An apparatus for determining the speed of sound in a fluid flowing in a pipe comprising: means for actively testing the flowing fluid with acoustic energy and producing a test signal corresponding to the speed of sound of the fluid, said testing means in contact with the pipe and disposed on the outside of the pipe and acoustic energy follows a path through the pipe wall, the testing means comprises a first transducer for transmitting acoustic signals through the fluid, said first transducer in acoustic contact with and disposed on the outside of said pipe; a second transducer for receiving the acoustic signals transmitted by the first transducer through the pipe wall, said second transducer disposed on the outside of said pipe in an opposing relationship with said first transducer such that the acoustic signals transmitted by the first transducer travel on a diametric path with respect to the pipe to the second transducer through the pipe wall; and signal processing means for determining the speed of sound of the flowing fluid based on the test signal, said testing means in communication with said signal processing means, the signal processing means includes means for determining the speed of sound in the fluid based on the transmission time of the acoustic signal transmitted between the first and second transducers through the pipe wall wherein the determining means determines the speed of sound according to the equation: t c =ID/c f +2 ·a pi +2 ·a wc /c w wherein t c is the average transit time along the diametrical path (second) between the first and second transducer, ID is the inside diameter of the pipe, a p is the wall thickness of the pipe (inches), a wc is the height of the pad, c w is the velocity of sound in the transducer wedge and pad (inches/sec), and c pi is the velocity of longitudinal wave in pipe (inches/sec).