Method and apparatus for analyzing traffic and a sensor therefor

An apparatus for detecting the speed of a magnetically permeable mass by disturbance of the earth's magnetic field adjacent the apparatus, the apparatus comprising:

• a)first and second magnetic field sensors each comprising:
• a magnetic field detector formed from a magnetically variable resistor;
• a first flux concentrator for concentrating magnetic flux towards the magnetically variable resistor;
• a biasing means for supplying an electrical bias to the magnetically variable resistor;
• an amplifier for sensing changes in the resistance of the magnetically variable resistor and for producing an output indicative thereof;
• a differentiator for differentiating the output of the amplifier;
• a zero slope detector for detecting the output of the differentiator and for generating a binary changing signal when the output of the differentiator is zero;
• b) a counter that accumulates values at a predetermined rate;
• and
• c) a processor for storing a first series of values of the counter in response to the zero slope detector of the first magnetic field sensor generating binary changing signals, for storing a second series of values of the counter in response to the zero slope detector of the second magnetic field sensor generating binary changing signals, for converting the first series of values into a first time series profile, for converting the second series of values into a second time series profile, for measuring a difference in time between equivalent positions in the first time series profile and the second time series profile and for calculating the speed of the mass as a function of the difference.

A method for counting vehicles passing a location, the method comprising the steps of:

• detecting changes in resistance of a first magnetically variable resistor in response to a vehicle passing thereby;
• generating a first analog signal corresponding to changes in the resistance of the first magnetically variable resistor;
• differentiating the first analog signal;
• producing a first binary changing signal that changes binary state when the slope of the differentiated first analog signal equals zero;
• recording a first series of times when the first binary changing signal changes binary state;
• producing from the recorded first series of times a first time series profile;
• and
• accumulating and storing a count of passing vehicles as a function of the first time series profile.

An apparatus for counting vehicles passing a location, the apparatus comprising:

• a first magnetically variable resistor positionable to detect changes in magnetic field at the location in response to vehicles passing thereby;
• an amplifier means connected to the first magnetically variable resistor for generating a first analog signal corresponding to the changes in the resistance of the first magnetically variable resistor;
• a converting means for converting the first analog signal into a first binary changing time series profile, with the first binary changing time series profile changing binary state when a slope of the first analog signal equals zero;
• and
• a storage means for accumulating and storing a count of passing vehicles.