ULTRASOUND SPEED MEASUREMENT OF TEMPERATURE AND PRESSURE EFFECTS

Abstract: An apparatus and process for using ultrasound to measure speed and acceleration in fluids is provided. Three preferred embodiments are disclosed. The first preferred embodiment measures fluid velocity, such as, for example, wind, under standard atmospheric pressure-temperature. The second preferred embodiment measures gas velocity, such as, for example, wind, affected by and automatically calibrates for pressure-temperature. The third preferred embodiment measures gas density, such as, for example, density altitude. Applications of the invention include wind direction and speed calculation in agriculture, aviation, hydraulics, and other industries. One of the advantages provided by the invention is there are no moving parts in making such measurements.

Description: Ultrasound Speed Measurement of Temperature and Pressure Effects BACKGROUND OF THE INVENTION TECHNICAL FIELD The invention relates to measurement of speed and acceleration of fluids. More particularly, the invention relates to an ultrasound technology, disclosed in U.S. Patent Application Serial No. 09/134,315 , filed August 14, 1998. DESCRIPTION OF THE PRIOR ART 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 travelling in the same direction is speeded up, while sound travelling 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 S 0 +W cos θ, where S 0 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/(S 0 +W cos θ). M. C. Heard, Wind Speed Measurement, U.S. Patent No. 4,336,606 (Jun. 22, 1982) discloses an apparatus for and a method of detecting and measuring wind gradient at a location, and involves a comparison of the wind speed in the same direction at two or more heights at the location. Said 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. The disclosed apparatus 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. M. J. Gill, Speed Measurement Device, U.S. Patent No. 5,163,331 (Nov. 17, 1992) discloses a fluid speed measurement device that includes a pair of ultrasonic transducers spaced in a measuring chamber. A transmitter and receiver system is controlled by a microprocessor which generates pulses which periodically invert and these are switched by switches that allow alternate direction of transmission. Reception and detection of signals is effected by particular blocks. Time calculation is determined by a counter and results are used to calculate flow speed or volume using a microprocessor. A speed increase in the measurement region is effected using a venturi device. The device disclosed in Gill is a closed device. In a closed configuration the speed of a gas is higher, than the speed of the same gas in an open configuration. The disclosed system therefore is not required to be sufficiently sensitive to detect signals in such a fluid wherein the speed is not so high, as in, for example, the atmosphere. Hermann et al, Method and Circuit Arrangement for the Measurement of Flow Speed by Means of Acoustical Transit Time Differences, U.S. Patent No. 5,804,739 (Sep. 8, 1998) discloses a Dmethod of determining the time point (to) of the start of a high frequency oscillation packet triggered as a result of a corresponding external excitation which is extremely tolerant relative to systematic disturbances from various sources that consists of determining the times at at least two points of the envelope curve of the oscillation packet with respect to an arbitrary zero time point. Of these two points one is a characteristic point of the envelope curve and the other has an amplitude equal to a predetermined fraction of the amplitude at the characteristic envelope curve point. It is preferable that during DDcalculation the angle between the directions of the ultrasonic pulse packets and the flow direction of the medium, Ddiffers significantly from 90. degree, is particularly taken into account. D Hermann et al does not disclose nor suggest automatic calibration for pressure-temperature, nor portability, no that the size of the measuring device be of a relative small size. It would advantageous to provide a fluid speed measurement apparatus along with a process that takes digital measurements so as to be more precise. It would advantageous to provide a fluid speed measurement apparatus along with a process that uses a protective, ventilated material, such as, for example, a lightweight plastic, so as to allow for automatic calibration to pressure-temperature. It would advantageous to provide a fluid speed measurement apparatus along with a process that is small enough and portable to be used at an airplane runway for measuring wind velocity and direction, yet placed far enough away from the runway so that loud airplane noises cannot interfere with the measurement apparatus and process. It would advantageous to provide a fluid speed measurement apparatus along with a process that has no moving parts, such as, for example, a ventilator or moving flap used in detecting fluid speed. SUMMARY OF THE INVENTION An apparatus and process for using ultrasound technology disclosed in U.S. Serial No. 09/134,315 pursuant to the Whiteboard project, to measure speed and acceleration in fluids are provided. Three preferred embodiments are disclosed. The first preferred embodiment measures fluid velocity, such as, for example, wind, under standard atmospheric pressure-temperature. The second preferred embodiment measures fluid velocity, such as, for example, wind, affected by and automatically calibrates for pressure and temperature. The third preferred embodiment measures gas or air density, such as, for example, density altitude. Applications of the invention include wind direction and speed calculation in agriculture, aviation, hydraulics, and other industries. One of the advantages provided by the invention is there are no moving parts in making such measurements. BRIEF DESCRIPTION OF THE DRAWINGS 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 Fig. 3 is a diagram of the third preferred embodiment, according to the invention. DETAILED DESCRIPTION OF THE INVENTION An apparatus and process for using ultrasound technology disclosed in U.S. Serial No. 09/134,315 pursuant to the Whiteboard project, to measure speed and acceleration in fluids are provided. Three preferred embodiments are disclosed. The first preferred embodiment measures fluid velocity, such as, for example, wind, under standard atmospheric pressure and temperature. The second preferred embodiment measures fluid velocity, such as, for example, wind, affected by and automatically calibrates for pressure and temperature. The third preferred 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. One of the advantages provided by the invention is there are no moving parts in making such measurements. Fig. 1 is a diagram of a first preferred embodiment of an apparatus for calculating a wind velocity vector in standard atmospheric pressure. A first transmitter element 10, T-i, is adapted to transmit ultrasonic pulses. A second transmitter element 20, T 2 , 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 40 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 , tι, from the first transmitter 10 to the receiver 30 is calculated. A second time transit vector 71 , t 2 , from the second transmitter 20 to the receiver 30 is calculated. A first transit time differential vector 80 is determined by taking the difference between the first transit time vector 61 and the predetermined transit time vector 60 of the generic ultrasonic pulse in standard atmospheric pressure. Similarly, a second transit time differential vector 81 is determined by taking the difference between the second transit time vector 71 and the predetermined transit time vector 70 of the generic ultrasonic pulse in standard atmospheric pressure. A resultant fluid velocity vector 82 is determined by combining the first transit time differential vector 80 and the second transit time differential vector 81. Fig. 2 is a diagram of a second preferred embodiment of an apparatus for calculating an automatically calibrated fluid velocity vector in external pressure-temperature. A first transmitter element 200 is adapted to transmit ultrasonic pulses, and a first transmitter primed element 201 is adapted to transmit ultrasonic pulses. The first transmitter element 200 is placed in an open configuration 250 and the first transmitter primed element 201 is placed in a ventilated tube 202. The first transmitter primed element 201 is positioned along a vertical axis of the first transmitter element 200. A second transmitter element 210 is adapted to transmit ultrasonic pulses, and a second transmitter primed element 211 is adapted to transmit ultrasonic pulses. The second transmitter element 210 is placed in the open configuration 250 and the second transmitter primed element 211 is placed in a second ventilated tube 212. The second transmitter primed element 211 is positioned along a second axis of the second transmitter element 210, wherein the second axis is perpendicular to the first axis. A receiver element 220 is adapted to receive ultrasonic pulses from the first transmitter 200, the first transmitter primed 201 , the second transmitter 210, and the second transmitter primed 211. The first transmitter 200 and the first transmitter primed 201 are each positioned a first short distance 240 from the receiver 220. The second transmitter 210 and the second transmitter primed 211 are each positioned a second short distance 241 from the receiver 220, and are each positioned at a 90 degree angle from 243 the first transmitter 200 and the first transmitter primed 201. A time transit vector 260 of an ultrasonic pulse from the receiver 220 to the first transmitter 200 in the open configuration 250 is a predetermined entity. A time transit vector 265 of an ultrasonic pulse from the receiver 220 to the first transmitter primed 201 in the ventilated tube is a predetermined entity. Similarly, a time transit vector 270 of an ultrasonic pulse from the receiver 220 to the second transmitter 210 in the open configuration 250 is a predetermined entity. A time transit vector 275 of an ultrasonic pulse from the receiver 220 to the second transmitter primed 211 in the ventilated tube is a predetermined entity. An ultrasonic time transit vector 261 , ti, from the first transmitter 200 to the receiver 220 is calculated. An ultrasonic time transit vector 266, from the first transmitter primed 201 to the receiver 220 is calculated. Similarly, a second ultrasonic time transit vector 271 , t 2 , from the second transmitter 210 to the receiver 220 is calculated. A second ultrasonic time transit primed vector 276, t 2 D , from the second transmitter primed 211 to the receiver 220 is calculated. A first transit time differential vector, Δt-i, by taking the difference between the calculated first transit time vector 261 and the predetermined time transit vector 260 is calculated. A first transit time differential vector primed, Δt π ι, by taking the difference between the calculated first transit time vector primed 266 and the predetermined time transit vector primed 265 is calculated. Similarly, a second transit time differential vector, Δt 2 , by taking the difference between the calculated second transit time vector 271 and the predetermined time transit vector 270 is calculated. A second transit time differential vector primed, Δt D 2 , by taking the difference between the calculated second transit time vector primed 276 and the predetermined time transit vector primed 275 is calculated. A first automatically calibrated fluid velocity component vector 280 is determined by taking the difference between the first transit time differential vector, Δt-i, and the first transit time differential vector primed, Δt D ι. Similarly, a second automatically calibrated fluid velocity component vector 281 is determined by taking the difference between the second transit time differential vector, Δt 2 , and the second transit time differential vector primed, Δt D 2 . A resultant automatically calibrated fluid velocity vector 282 is determined by combining the component vectors, 280 and 281. Fig. 3 is a diagram of a third preferred embodiment of an apparatus for calculating density measurement in external pressure-temperature. A transmitter element 300, T, is adapted to transmit ultrasonic pulses and placed in a ventilated tube 302. A receiver element 320 is adapted to receive ultrasonic pulses. The tubed transmitter 300 is positioned a short distance the receiver 320. An ultrasonic pulse is transmitted from the tubed transmitter 300 to the receiver 320 and a transit time 361 for the pulse to reach the receiver 320 is calculated. A transit time differential measurement by taking a difference between the calculated transit time 361 and a predetermined transit time 360 of a generic ultrasonic pulse transmitted from the receiver 320 to the first transmitter 300 in standard atmospheric pressure. A density measurement is determined from the transit time differential measurement. It should be appreciated that the first two embodiments work particularly well when the fluid whose speed is calculated is wind. The third embodiment works particularly well for calculating density altitude. It should be noted that all three preferred embodiments are small, and therefore lightweight and relatively inexpensive. For example, a preferred distance between any transmitter and the receiver is approximately two feet. It should be noted that all three preferred embodiments are adaptable to be portable. For example, the open transmitters and tubed transmitters can be coupled to foldable lightweight legs that fold open and closed for transporting by a person. It should be noted that in the open configuration, the receiver is sufficiently sensitive to receive the ultrasonic pulses. It should be noted that a preferred material for the ventilated tube is a lightweight plastic protective material. It should be noted that in all three preferred embodiments, the measurements taken are digital, as opposed to analogue, and are therefore more accurate. It should be noted that in all three preferred embodiments, there are no moving parts to make the invention, for example, cumbersome, and to be distracting to a user. Accordingly, although the invention has been described in detail with reference to three particular preferred embodiments, persons possessing ordinary skill in the art to which this invention pertains will appreciate that various modifications and enhancements may be made without departing from the spirit and scope of the claims that follow.

Claims: CLAIMS 1. A process for calculating a gas velocity vector in standard atmospheric pressure, comprising the steps of: providing a first transmitter element adapted to transmit ultrasonic pulses, a second transmitter element adapted to transmit ultrasonic pulses and a receiver element adapted to receive ultrasonic pulses, whereby said first transmitter is positioned a first short distance from said receiver, said second transmitter is positioned a second short distance from said receiver and positioned at a 90 degree angle from said first transmitter, and said three elements are placed in an open configuration; transmitting a first ultrasonic pulse from said first transmitter to said receiver and calculating a first transit time for said first pulse to reach said receiver; transmitting a second ultrasonic pulse from said second transmitter to said receiver and calculating a second transit time for said second pulse to reach said receiver; calculating a first transit time differential vector by taking a first difference between said calculated first transit time and a first predetermined transit time of a generic ultrasonic pulse transmitted from said receiver to said first transmitter in standard atmospheric pressure; calculating a second transit time differential vector by taking a second difference between said calculated second transit time and a second predetermined transit time of said generic ultrasonic pulse transmitted from said receiver to said second transmitter in standard atmospheric pressure; and determining said gas velocity vector by combining said first transit time differential vector and said second transit time differential vector. 2. The process of Claim 1 , wherein said gas is wind. 3. The process of Claim 1 , wherein said first short distance is two feet and said second short distance is two feet. 4. The process of Claim 1 , wherein said positioned first transmitter, said positioned second transmitter, and said receiver are adapted to be portable. 5. The process of Claim 1 , wherein said receiver adapted to receive ultrasonic pulses is sufficiently sensitive to receive said pulses in said open configuration. 6. The process of Claim 1 , wherein said first transmitter is an ultrasonic piezoelectric transducer and said second transmitter is an ultrasonic piezoelectric transducer. 7. The process of Claim 1 , wherein said calculations are digital. 8. The process of Claim 1 , further providing no moving parts. 9. An apparatus for calculating a gas velocity vector in standard atmospheric pressure, comprising: a first transmitter element adapted to transmit ultrasonic pulses, a second transmitter element adapted to transmit ultrasonic pulses, a receiver element adapted to receive ultrasonic pulses, whereby said first transmitter is positioned a first short distance from said receiver, said second transmitter is positioned a second short distance from said receiver and positioned at a 90 degree angle from said first transmitter, and said three elements are placed in an open configuration; means for transmitting a first ultrasonic pulse from said first transmitter to said receiver and calculating a first transit time for said first pulse to reach said receiver; means for transmitting a second ultrasonic pulse from said second transmitter to said receiver and calculating a second transit time for said second pulse to reach said receiver; means for calculating a first transit time differential vector by taking a first difference between said calculated first transit time and a first predetermined transit time of a generic ultrasonic pulse transmitted from said receiver to said first transmitter in standard atmospheric pressure; means for calculating a second transit time differential vector by taking a second difference between said calculated second transit time and a second predetermined transit time of said generic ultrasonic pulse transmitted from said receiver to said second transmitter in standard atmospheric pressure; and means for determining said gas velocity vector by combining said first transit time differential vector and said second transit time differential vector. 10. The apparatus of Claim 9, wherein said gas is wind. 11. The apparatus of Claim 9, wherein said first short distance is two feet and said second short distance is two feet. 12. The apparatus of Claim 9, wherein said positioned first transmitter, said positioned second transmitter, and said receiver are adapted to be portable. 13. The apparatus of Claim 9, wherein said receiver adapted to receive ultrasonic pulses is sufficiently sensitive to receive said pulses in said open configuration. 14. The apparatus of Claim 9, wherein said first transmitter is an ultrasonic piezoelectric transducer and said second transmitter is an ultrasonic piezoelectric transducer. 15. The apparatus of Claim 9, wherein said calculations are digital. 16. The apparatus of Claim 9, further comprising no moving parts. 17. A process for calculating an automatically calibrated gas velocity vector in external pressure-temperature, comprising the steps of: providing a first transmitter element adapted to transmit ultrasonic pulses, and a first transmitter primed element adapted to transmit ultrasonic pulses, wherein said first transmitter element is placed in an open configuration, and wherein said first transmitter primed element is placed in a first ventilated tube, such that said first transmitter primed element is positioned along a first axis of said first transmitter element; providing a second transmitter element adapted to transmit ultrasonic pulses, and a second transmitter primed element adapted to transmit ultrasonic pulses, wherein said second transmitter element is placed in said open configuration, and wherein said second transmitter primed element is placed in a second ventilated tube, such that said second transmitter primed element is positioned along a second axis of said second transmitter element, said second axis perpendicular to said first axis; providing a receiver element adapted to receive ultrasonic pulses from said first transmitter, said first transmitter primed, said second transmitter, and said second transmitter primed, whereby said first transmitter and said first primed transmitter are each positioned a first short distance from said receiver, said second transmitter and second primed transmitter are each positioned a second short distance from said receiver and are each positioned at a 90 degree angle from said first transmitter and said first primed transmitter; transmitting a first ultrasonic pulse from said first transmitter to said receiver and calculating a first transit time for said first pulse to reach said receiver; transmitting a first primed ultrasonic pulse from said first primed transmitter to said receiver and calculating a first primed transit time for said first primed pulse to reach said receiver; transmitting a second ultrasonic pulse from said second transmitter to said receiver and calculating a second transit time for said second pulse to reach said receiver; transmitting a second primed ultrasonic pulse from said second primed transmitter to said receiver and calculating a second primed transit time for said second primed pulse to reach said receiver; calculating a first transit time differential vector by taking a first difference between said calculated first transit time vector and a first predetermined time transit vector; calculating a first transit time differential vector primed by taking a first difference primed between said calculated first transit time vector primed and a first predetermined time transit vector primed; calculating a second transit time differential vector by taking a second difference between said calculated second transit time vector and a second predetermined time transit vector; calculating a second transit time differential vector primed by taking a second difference primed between said calculated second transit time vector primed and a second predetermined time transit vector primed; calculating a first automatically calibrated gas velocity component vector by taking a first differential difference between said calculated first transit time differential vector and said calculated first transit time differential vector primed; calculating a second automatically calibrated gas velocity component vector by taking a second differential difference between said calculated second transit time differential vector and said calculated second transit time differential vector primed; and determining said automatically calibrated fluid velocity vector by combining said first automatically calibrated gas velocity component vector and said second automatically calibrated fluid velocity component vector . 18. The process of Claim 17, wherein said gas is wind. 19. The process of Claim 7, wherein said first short distance is two feet and said second short distance is two feet. 20. The process of Claim 17, wherein said positioned first transmitter element, said positioned first transmitter primed element placed in said first ventilated tube, said positioned second transmitter element, said positioned second transmitter primed element placed in said second ventilated tube, and said receiver are adapted to be portable. 21. The process of Claim 17, wherein said receiver adapted to receive ultrasonic pulses is sufficiently sensitive to receive said pulses in said open configuration. 22. The process of Claim 17, wherein said first transmitter, said first transmitter primed, said second transmitter, and said second transmitter primed are each an ultrasonic piezoelectric transducer. 23. The process of Claim 17, wherein said calculations are digital. 24. The process of Claim 17, further providing no moving parts. 25.. The process of Claim 17, wherein said first ventilated tube and second ventilated tube is made of a lightweight, plastic, protective material. 26. An apparatus for calculating an automatically calibrated gas velocity vector in external pressure-temperature, comprising: a first transmitter element adapted to transmit ultrasonic pulses, and a first transmitter primed element adapted to transmit ultrasonic pulses, wherein said first transmitter element is placed in an open configuration, and wherein said first transmitter primed element is placed in a first ventilated tube, such that said first transmitter primed element is positioned along a first axis of said first transmitter element; a second transmitter element adapted to transmit ultrasonic pulses, and a second transmitter primed element adapted to transmit ultrasonic pulses, wherein said second transmitter element is placed in said open configuration, and wherein said second transmitter primed element is placed in a second ventilated tube, such that said second transmitter primed element is positioned along a second axis of said second transmitter element, said second axis perpendicular to said first axis; a receiver element adapted to receive ultrasonic pulses from said first transmitter, said first transmitter primed, said second transmitter, and said second transmitter primed, whereby said first transmitter and said first primed transmitter are each positioned a first short distance from said receiver, and said second transmitter and second primed transmitter are each positioned a second short distance from said receiver and are each positioned at a 90 degree angle from said first transmitter and said first primed transmitter; means for transmitting a first ultrasonic pulse from said first transmitter to said receiver and calculating a first transit time for said first pulse to reach said receiver; means for transmitting a first primed ultrasonic pulse from said first primed transmitter to said receiver and calculating a first primed transit time for said first primed pulse to reach said receiver; means for transmitting a second ultrasonic pulse from said second transmitter to said receiver and calculating a second transit time for said second pulse to reach said receiver; means for transmitting a second primed ultrasonic pulse from said second primed transmitter to said receiver and calculating a second primed transit time for said second primed pulse to reach said receiver; means for calculating a first transit time differential vector by taking a first difference between said calculated first transit time vector and a first predetermined time transit vector; means for calculating a first transit time differential vector primed by taking a first difference primed between said calculated first transit time vector primed and a first predetermined time transit vector primed; means for calculating a second transit time differential vector by taking a second difference between said calculated second transit time vector and a second predetermined time transit vector; means for calculating a second transit time differential vector primed by taking a second difference primed between said calculated second transit time vector primed and a second predetermined time transit vector primed; means for calculating a first automatically calibrated gas velocity component vector by taking a first differential difference between said calculated first transit time differential vector and said calculated first transit time differential vector primed; means for calculating a second automatically calibrated gas velocity component vector by taking a second differential difference between said calculated second transit time differential vector and said calculated second transit time differential vector primed; and means for determining said automatically calibrated gas velocity vector by combining said first automatically calibrated gas velocity component vector and said second automatically calibrated fluid velocity component vector . 27. The apparatus of Claim 26, wherein said gas is wind. 28. The apparatus of Claim 26, wherein said first short distance is two feet and said second short distance is two feet. 29. The apparatus of Claim 26, wherein said positioned first transmitter element, said positioned first transmitter primed element placed in said first ventilated tube, said positioned second transmitter element, said positioned second transmitter primed element placed in said second ventilated tube, and said receiver are adapted to be portable. 30. The apparatus of Claim 26, wherein said receiver adapted to receive ultrasonic pulses is sufficiently sensitive to receive said pulses in said open configuration. 31. The apparatus of Claim 26, wherein said first transmitter, said first transmitter primed, said second transmitter, and said second transmitter primed are each an ultrasonic piezoelectric transducer. 32. The apparatus of Claim 26, wherein said calculations are digital. 33. The apparatus of Claim 26, further providing no moving parts. 34. The apparatus of Claim 26, wherein said first ventilated tube and second ventilated tube is made of a lightweight, plastic, protective material. 35. A process for calculating density measurement in external pressure- temperature, comprising the steps of: providing a transmitter element adapted to transmit ultrasonic pulses and placed in a ventilated tube, and a receiver element adapted to receive ultrasonic pulses, whereby said tubed transmitter is positioned a short distance from said receiver; transmitting an ultrasonic pulse from said tubed transmitter to said receiver and calculating a transit time for said pulse to reach said receiver; calculating a transit time differential measurement by taking a difference between said calculated transit time and a predetermined transit time of a generic ultrasonic pulse transmitted from said receiver to said first transmitter in standard atmospheric pressure; and determining said density measurement from said transit time differential measurement. 36. The process of Claim 35, wherein said density measurement is density altitude. 37. The process of Claim 35, wherein said short distance is two feet. 38. The process of Claim 35, wherein said transmitter element in said ventilated tube and said receiver are adapted to be portable. 39. The process of Claim 35, wherein said transmitter is an ultrasonic piezoelectric transducer. 40. The process of Claim 35, wherein said calculations are digital. 41. The process of Claim 35, further providing no moving parts. 42. The process of Claim 35, wherein said ventilated tube is made of a lightweight, plastic, protective material. 43. An apparatus for calculating density measurement in external pressure-temperature, comprising: a transmitter element adapted to transmit ultrasonic pulses and placed in a ventilated tube, and a receiver element adapted to receive ultrasonic pulses, whereby said tubed transmitter is positioned a short distance from said receiver; means for transmitting an ultrasonic pulse from said tubed transmitter to said receiver and calculating a transit time for said pulse to reach said receiver; means for calculating a transit time differential measurement by taking a difference between said calculated transit time and a predetermined transit time of a generic ultrasonic pulse transmitted from said receiver to said first transmitter in standard atmospheric pressure; and means for determining said density measurement from said transit time differential measurement. 44. The apparatus of Claim 43, wherein said density measurement is density altitude. 45. The apparatus of Claim 43, wherein said short distance is two feet. 46. The apparatus of Claim 43, wherein said transmitter element in said ventilated tube and said receiver are adapted to be portable. 47. The apparatus of Claim 43, wherein said transmitter is an ultrasonic piezoelectric transducer. 48. The apparatus of Claim 43, wherein said calculations are digital. 49. The apparatus of Claim 43, further providing no moving parts. 50. The apparatus of Claim 43, wherein said ventilated tube is made of a lightweight, plastic, protective material.

Inventors: HAREL JACOB, HOU ALFRED SAMSON, PLOTKIN SERGE, WOOD ROBERT P, HAREL, JACOB, HOU, ALFRED, SAMSON, PLOTKIN, SERGE, WOOD, ROBERT, P.
Applicants: ELECTRONICS FOR IMAGING INC, ELECTRONICS FOR IMAGING, INC.
Application year: 2001
Main classification: G01P5
IPC codes: G01P5, G01P13