Ultrasound speed measurement of temperature and pressure

#The invention relates to measurement of speed and acceleration of fluids, in particular with regard to ultrasound technology.

#The speed of sound in air along a line or path between any two points may be determined by measuring the time taken for the sound to travel between the two points. With the air moving from one point to the other, sound traveling in the same direction is speeded up, while sound traveling in the other direction is slowed down. Where the actual wind has a speed W in a direction which is at an angle θ to the sound speed line, then the wind component along that line is W cos θ, and the wind component along a line that is perpendicular to the sound speed line is W sin θ. In such a case, the sound speed S along the line is So+W cos θ, where So is the sound speed in still air. If the distance over which the sound speed is being measured is D, then the time T taken is D/S. Thus, T=D/(So+W cos θ).

#Heard U.S. Pat. No. 4,336,606 (“Heard) discloses methods and apparatus for detecting and measuring a wind gradient at a location by comparing the wind speed in the same direction at two or more heights at the location. The comparison based upon a comparison of the speed of sound in a direction and at specific heights, a difference in the apparent speeds indicating the presence of wind gradient. The disclosure involves: beaming a regular sound wave train between a transmitter/receiver pair positioned and like orientated at each of two or more heights at the location; noting each transceiver pair's received sound wave train phase, and comparing it with its transmitted phase, so as to deduce the wind-caused phase change; and using these deduced phase changes to calculate the actual wind speeds, and thus the relative changes of wind speed with height, in the selected direction. Heard's apparatus, however, has the transmitter/receiver pairs positioned at too great a distance (approximately 200 feet) for the measurement to be effective and accurate. In addition, applying the teachings to an airplane landing situation is not practical as the noise level of an incoming plane is too large and will interfere with the accurate and timely measurements of the ultrasound transmissions.

#The above-mentioned objects and features of the present invention can be more clearly understood from the following detailed description considered in conjunction with the following drawings, in which the same reference numerals denote the same elements throughout, and in which:

#FIG. 1 is a diagram of the first preferred embodiment, according to the invention;

#FIG. 2 is a diagram of the second preferred embodiment, according to the invention; and

#Methods and apparatus for using ultrasound technology to measure speed and acceleration in fluids are provided. Three preferred embodiments are disclosed. The first exemplary embodiment measures fluid velocity, such as, for example, wind, under standard atmospheric pressure and temperature. The second exemplary embodiment measures fluid velocity, such as, for example, wind, affected by and automatically calibrates for pressure and temperature. The third exemplary embodiment measures fluid density, such as, for example, density altitude. Applications of the invention include wind direction and speed calculation in agriculture, aviation, hydraulics, and other industries.

#FIG. 1 is a diagram of a first exemplary embodiment of an apparatus for calculating a wind velocity vector in standard atmospheric pressure. A first transmitter element 10, T1, is adapted to transmit ultrasonic pulses. A second transmitter element 20, T2, is also adapted to transmit ultrasonic pulses. A receiver element 30 is adapted to receive ultrasonic pulses. The first transmitter 10 is positioned a relatively short distance of about 2 feet from the receiver 30. The second transmitter 20 is also positioned a short distance 41 of about 2 feet from the receiver 30 and positioned at a 90 degree angle 43 from the first transmitter 10. The first transmitter 10, the second transmitter 20, and the receiver 30 are placed in an open configuration 50.

#The time transit vector 60 of a generic ultrasonic pulse from the receiver 30 to the first transmitter 10 in standard atmospheric pressure with no wind is a predetermined entity. Similarly, the time transit vector 70 of a generic ultrasonic pulse from the receiver 30 to the second transmitter 20 in standard atmospheric pressure with no wind is a predetermined entity. A time transit vector 61, t1, from the first transmitter 10 to the receiver 30 is calculated. A second time transit vector 71, t2, from the second transmitter 20 to the receiver 30 is calculated.