Acoustic ranging system
First Claim
1. In an acoustic ranging system comprising at least one transducer directed towards the surface of material whose level is to be determined, a transmitter to energize selectively each said transducer whereby to cause it to emit at least one shot of high frequency sound, and a receiver receiving and amplifying energy from said at least one shot echoed back to said transducer over a subsequent period, the time lapse after a shot before receipt of an echo being proportional to the distance of the origin of the echo, the improvement wherein:
- signal processing means are provided comprising analog to digital converter means to sample repeatedly the output amplitude of the signal from the receiver at defined intervals and to digitize the samples;
memory means to store an extended sequence of digitized samples so produced in respect of at least one shot and form therefrom a digital data base depicting an amplitude/time profile of the received signal with a resolution dependent on the sampling intervals;
means to utilize the amplitude profile depicted by the data in said data base to help isolate relative to a time axis a portion of the output signal produce by at least one shot deemed most probable to correspond to a wanted echo; and
means to determine a range represented by an echo within said portion of the time axis.
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Abstract
In an acoustic ranging system, an echo signal received following a shot is repeatedly sampled and the samples digitized to produce a statistical data base representing the received echo profile which can be analyzed by various methods to determine the point on the time axis of the profile which corresponds to a wanted echo, and the degree of confidence with which the wanted echo has been identified. The number of shots taken depends upon the conditions at the site being monitored and upon the degree of confidence with which the wanted echo has been determined, and the order in which points in a multipoint system are monitored is determined by an adaptive scanning system which directs shots to different points following a system determined by a predetermined hierarchy, by the results provided by previous shots, by the conditions existing at different points, and by the receipt of outside signals. In order to improve resolution beyond that permitted by the sampling rate selected, the data base produced may be used as an adjunct to an analog determination of the actual elapsed time before receipt of a wanted echo, either by using the data base to determine a temporal "window" within which a wanted echo may be expected, and the expected amplitude of that echo, so that an accurate analog determination of the receipt of a wanted echo becomes possible, or by using the data base to provide an adaptive time variant gain control signal for the echo signal receiver so as to facilitate analog detection of the wanted echo.
139 Citations
21 Claims
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1. In an acoustic ranging system comprising at least one transducer directed towards the surface of material whose level is to be determined, a transmitter to energize selectively each said transducer whereby to cause it to emit at least one shot of high frequency sound, and a receiver receiving and amplifying energy from said at least one shot echoed back to said transducer over a subsequent period, the time lapse after a shot before receipt of an echo being proportional to the distance of the origin of the echo, the improvement wherein:
signal processing means are provided comprising analog to digital converter means to sample repeatedly the output amplitude of the signal from the receiver at defined intervals and to digitize the samples;
memory means to store an extended sequence of digitized samples so produced in respect of at least one shot and form therefrom a digital data base depicting an amplitude/time profile of the received signal with a resolution dependent on the sampling intervals;
means to utilize the amplitude profile depicted by the data in said data base to help isolate relative to a time axis a portion of the output signal produce by at least one shot deemed most probable to correspond to a wanted echo; and
means to determine a range represented by an echo within said portion of the time axis.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
Specification