Method and apparatus for analying traffic and a sensor therefor
First Claim
1. A sensor for detecting a magnetically permeable mass by the disturbance of the earth'"'"'s magnetic field in the vicinity of the sensor comprising:
- a) a ferromagnetic strip with a conductive winding wrapped thereabout, wherein the ferromagnetic strip may be biased in a position on its BH curve where the slope is substantially linear,b) means for magnetically biasing the strip such that regardless of the orientation of the earth'"'"'s magnetic field and the strip, the ferromagnetic strip is biased within a range on its said BH curve where the slope is substantially linear and such that a disturbance of the earth'"'"'s magnetic field does not move the magnetization of the ferromagnetic strip substantially out of this range,c) means for generating an analog signal indicative of the inductance of the winding as the earth'"'"'s magnetic field is disturbed in the vicinity of the ferromagnetic strip causing a change in the inductance of the winding,d) means for digitizing the analog signal at spaced time intervals to produce a series of digitized values, ande) digital computer means for processing the digitized signal values to characterize the presence of the permeable mass.
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Accused Products
Abstract
A sensor for detecting a magnetically permeable mass by the disturbance of the earth'"'"'s magnetic field in the vicinity of the sensor comprises a ferromagnetic strip with a conductive winding wrapped thereabout, a means for magnetically biasing the strip such that regardless of orientation the earth'"'"'s magnetic field and the strip placing the ferromagnetic strip in a position on its BH curve where the slope is substantially linear, a means for generating an analog signal indicative of the inductance of the winding as the earth'"'"'s magnetic field is disturbed in the vicinity of the ferromagnetic strip causing a change in the inductance of the winding, a means for digitizing the analog signal at spaced time intervals to produce a series of digitized values, and a digital computer means for processing the digitized signal values to characterize the presence and/or motion of the permeable mass.
21 Citations
19 Claims
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1. A sensor for detecting a magnetically permeable mass by the disturbance of the earth'"'"'s magnetic field in the vicinity of the sensor comprising:
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a) a ferromagnetic strip with a conductive winding wrapped thereabout, wherein the ferromagnetic strip may be biased in a position on its BH curve where the slope is substantially linear, b) means for magnetically biasing the strip such that regardless of the orientation of the earth'"'"'s magnetic field and the strip, the ferromagnetic strip is biased within a range on its said BH curve where the slope is substantially linear and such that a disturbance of the earth'"'"'s magnetic field does not move the magnetization of the ferromagnetic strip substantially out of this range, c) means for generating an analog signal indicative of the inductance of the winding as the earth'"'"'s magnetic field is disturbed in the vicinity of the ferromagnetic strip causing a change in the inductance of the winding, d) means for digitizing the analog signal at spaced time intervals to produce a series of digitized values, and e) digital computer means for processing the digitized signal values to characterize the presence of the permeable mass.
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2. A sensor for detecting a magnetically permeable mass by the disturbance of the earth'"'"'s magnetic field in the vicinity of the sensor comprising:
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a) a ferromagnetic strip with a conductive winding wrapped thereabout, wherein the ferromagnetic strip may be biased in a position on its BH curve where the slope is substantially linear, b) a permanent magnet positioned near the ferromagnetic strip selected and positioned such that regardless of the orientation of the earth'"'"'s magnetic field and the strip, the ferromagnetic strip is biased within a range on its said BH curve where the slope is substantially linear and such that a disturbance of the earth'"'"'s magnetic field does not move the magnetization of the ferromagnetic strip substantially out of this range, c) means for generating an analog signal indicative of the inductance of the winding as the earth'"'"'s magnetic field is disturbed in the vicinity of the ferromagnetic strip causing a change in the inductance of the winding, said generating means comprising; i) a tank circuit in which the conductive winding is a component, the tank circuit being tuned to a selected frequency and having an input and an output, ii) an oscillator for applying a signal at the selected frequency to the input of the tank circuit, iii) a demodulator circuit for demodulating the signal at the output of the tank circuit, d) means for digitizing the analog signal at spaced time intervals to produce a series of digitized values, and e) digital computer means for processing the digitized signal values to characterize the motion of the permeable mass, said digital computer programmed to filter the digitized values and to locate patterns in the filtered values indicative of the passing of a magnetically permeable mass through the vicinity of the sensor.
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3. Apparatus for detecting the speed of a magnetically permeable mass by the disturbance of the earth'"'"'s magnetic field in the vicinity of the two sensors comprising:
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a) first and second magnetic sensors each comprising; i) a ferromagnetic strip with a conductive winding wrapped thereabout, wherein the ferromagnetic strip may be biased within a range on its BH curve where the slope is substantially linear, ii) means for magnetically biasing the ferromagnetic strip such that regardless of the orientation of the earth'"'"'s magnetic field and the strip, the ferromagnetic strip is biased in a position on its said BH curve where the slope is substantially linear and such that a disturbance of the earth'"'"'s magnetic field does not move the magnetization of the ferromagnetic strip substantially out of this range, b) means for generating an analog signal indicative of the inductance of the winding in the first and second sensors as the earth'"'"'s magnetic field is disturbed in the vicinity of the ferromagnetic strips causing a change in the inductance of the winding, c) means for digitizing the analog signals at spaced time intervals to produce two series of digitized values, and d) digital computer means for processing the two series of digitized signal values to two series of filtered digitized signal values and for comparing the two series of filtered values to find spaced, equivalent positions in the series, measuring the elapsed time between equivalent positions in each series and calculating the speed of the mass as an inverse function of the elapsed time.
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4. An apparatus for counting vehicles passing a fixed road position, said apparatus comprising:
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a) first and second magnetic field detectors spaced a fixed distance apart along the direction of travel of the vehicles which generate first and second analog signals indicative of magnetic field strength at the detectors and the passage of vehicles thereby, said magnetic field detectors comprising; i) a ferromagnetic strip with a conductive winding wrapped thereabout, wherein the strip may be biased within a range on its BH curve where the slope is substantially linear, ii) means for magnetically biasing the strip such that regardless of the orientation of the earth'"'"'s magnetic field and the ferromagnetic strip is biased within a range on said BH curve where the slope is substantially linear and such that a disturbance of the earth'"'"'s magnetic field does not move the magnetization of the ferromagnetic strip substantially out of this range, b) means for converting the first and second analog signals to first and second digital sequences, respectively, each comprised of a plurality of digitized signal values converted at spaced time internals, c) means including a digital computer for processing the first and second digital sequences to detect spaced equivalent positions in each sequence, d) means for accumulating and storing a count of passing vehicles, and e) means for measuring the elapsed time between the spaced, equivalent positions in each sequence and calculating the speed of said vehicle whereby the count may be classified according to speed. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification