Distance measurement system
First Claim
1. A method of measuring the distance between a first point and a second point in space, comprising the steps of:
- generating and frequency modulating an ultrasonic signal using binary frequency shift keying,transmitting the modulated signal from the first point towards the second point;
reflecting the transmitted signal at the second point back towards the first point;
receiving the reflected signal at the first point, andphase digitising the received signal by recording data pairs comprising time and place of zero-crossing transitions of the received signal, andanalysing the recorded transitions in a domain using only the time and phase data so as to determine the distance between the first point and the second point.
1 Assignment
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Accused Products
Abstract
Apparatus and a method using ultrasonic signals to determine the distance between the displacement of two points in space. An ultrasonic distance measurement unit (1) generates frequency modulated ultrasonic waves using binary shift keying. The signals are transmitted by the transmitting transducer (2) towards a reflector assembly (30), preferably comprised of two reflectors (31, 32). One of the reflectors (31) is smaller than the other reflector (32), and the smaller reflector (31) is positioned in front of the larger reflector (32). The reflected signals are received by the receiving transducer (3). The unit (1) phase digitizes and processes the received signal by recording time stamps of zero-crossings of the received signal. The speed of sound may be determined by a temperature measurement system (5) and/or by measuring the transit time difference between the two reflectors (31, 32) of the assembly (30). The distance between the unit (1) and the assembly (30) can then be determined from the speed of sound and the time taken for an ultrasonic signal to travel between the unit (1) and assembly (30). Displacement of the assembly (30) relative to the unit (1) can be determined by making distance measurements over a period of time. The present invention has a number of applications, including measurement of roof convergence in underground mining.
27 Citations
12 Claims
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1. A method of measuring the distance between a first point and a second point in space, comprising the steps of:
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generating and frequency modulating an ultrasonic signal using binary frequency shift keying, transmitting the modulated signal from the first point towards the second point; reflecting the transmitted signal at the second point back towards the first point; receiving the reflected signal at the first point, and phase digitising the received signal by recording data pairs comprising time and place of zero-crossing transitions of the received signal, and analysing the recorded transitions in a domain using only the time and phase data so as to determine the distance between the first point and the second point. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of measuring the distance between a first point and a second point in space, comprising the steps of:
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generating and frequency modulating an ultrasonic signal using binary frequency shift keying by transmitting a first signal segment having a first frequency followed by a second signal segment having a second frequency, where the transition from the first frequency to the second frequency occurs at a time to ; transmitting the modulated signal from the first point towards the second point; reflecting the transmitted signal at the second point back towards the first point; receiving the reflected signal at the first point and digitising the received signal by recording data pairs comprising the time and phase of the received signal at zero-crossing transitions of the received signal; and analysing the recorded transitions so as to determine the distance between the first point and the second point by processing the data pairs of the phase of the received signal against time by; (a) finding a first line of best fit for data pairs corresponding to the first signal segment, (b) finding a second line of best fit for data pairs corresponding to the second signal segment, and (c) finding the point of intersection of the first and second lines of best fit; whereby the time of the intersection of the first and second lines of best fit corresponds to the transition time of the ultrasonic signal from time to.
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9. An apparatus for measuring the distance between a first point and a second point in space, comprising:
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an ultrasonic signal generator at the first point for producing, in use, a frequency modulated ultrasonic signal using binary frequency shift keying and transmitting the modulated signal, a reflector at the second point capable of reflecting the transmitted signal, a receiver at the first point capable of receiving the reflected signal, signal processing means for phase digitising the received signal by recording data pairs comprising time and place of zero-crossing transitions of the received signal and for analysing the recorded transitions in a domain using only the time and phase data so as to determine the distance between the first point and the second point. - View Dependent Claims (10, 11, 12)
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Specification