Metal detector method and apparatus
OwnerGeorge Paltoglouinventor
Life of this patent
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Abstract
In a transient electromagnetic or pulse induction type metal detecting apparatus having a receiving coil attached to a sensor, a method and apparatus is disclosed of determining a null point comprising determining a series of post transient output values for the sensor at predetermined times; forming a summation of the output values or their negatives; and altering the predetermined times so as to minimise the summation.
Claims11
In a transient electromagnetic or pulse induction type metal detecting apparatus having a receiving coil attached to a sensor, a method of distinguishing between ferromagnetic and conductive materials comprising the steps of:
- monitoring the decay curve of the response of a transient pulse;
- generating a best fit of the decay curve using a function that has exponential and power law components;
- and
- utilising said best fit or deviations from said curve as a measure of the likelihood of detection of ferromagnetic or conductive materials by said apparatus.
In a transient electromagnetic or pulse induction type metal detecting apparatus having a receiving coil attached to a sensor, a method of distinguishing between ferromagnetic and conductive materials comprising the steps of:
- utilising a series of transient pulses of different length;
- monitoring the decay curve of the response to each of said transient pulses;
- comparing the decay curve of different length transient pulses to a function having exponential and power law components;
- and
- utilising said comparison as an indicator of the type of material detected by said apparatus.
An apparatus for detecting a metal or mineral object in a surrounding medium with a reduced sensitivity to external electromagnetic interference comprising:
- a transmission search coil for transmitting a magnetic field;
- a transmission apparatus for energising the transmission search coil with a substantially rectangular voltage producing a pulsed waveform;
- a receive coil for detecting the changes in the surrounding magnetic field through a voltage induced across the receive coil by changes in the magnetic flux;
- a measuring means for measuring the voltage across the receive coil at 3 or more selected time intervals after the end of a transmission pulse;
- and
- a processing means for processing said voltages such that a null summation is produced for a target medium by altering the time intervals and linearly combining the voltages across the receive coil at the time intervals to produce a ground balanced null signal substantially satisfying the following equations
- ΣkiVi=0 and Σki=0;
- wherein Vi is the voltage at the ith time interval after the end of the transmission pulse and ki is a multiplicative factor.
An apparatus for detecting a metal or mineral object in a surrounding medium comprising:
- a transmission search coil for transmitting a magnetic field;
- a transmission apparatus for energising the transmission search coil with a substantially rectangular voltage waveform producing a pulsed waveform that has pulses of two different, widths;
- a receive coil for detecting the changes in the surrounding magnetic field through a voltage induced across the coil by changes in the magnetic flux
- a measuring means for measuring the voltage across the receive coil at a selected time interval after the end of a transmission pulse, the time interval being alterable;
- a processing means of processing the said voltages, and altering the transmission pulse width, and altering the receive timing interval such that a null summation is produced for a target medium.
An apparatus for detecting a metal or mineral object in a surrounding medium with reduced sensitivity to ferromagnetic materials comprising:
- a transmission search coil for transmitting a magnetic field;
- a transmission apparatus for energising the transmission search coil with a substantially rectangular voltage waveform producing a pulsed waveform that has pulses of two different, widths;
- a receive coil for detecting the changes in the surrounding magnetic field through a voltage induced across the receive coil by changes in the magnetic flux;
- measuring means for measuring the voltage across the receive coil at two selected time intervals after the end of a transmission pulse, the time intervals being alterable;
- processing means for processing the said voltages, altering the transmission pulse width, and altering the receive timing interval such that a null summation is substantially produced for a target medium.
An apparatus for detecting a metal or mineral object in a surrounding medium with reduced sensitivity to ferromagnetic materials comprising:
- a transmission coil for transmitting a magnetic field;
- a transmission apparatus for energising the search coil with a substantially rectangular voltage producing a pulsed waveform that has pulses of at least three different, widths;
- a receive coil for detecting the changes in the surrounding magnetic field through a voltage induced across the receive coil by changes in the magnetic flux;
- measurement means for measuring the voltage across the receive coil at two selected time intervals after the end of a transmission pulse, the time intervals being alterable;
- and
- processing means for processing the said voltages, altering the transmission pulse width, and altering the receive timing interval such that a null summation is produced for a target medium.
An apparatus for detecting a metal or mineral object in a surrounding medium with a reduced sensitivity to external electromagnetic interference comprising:
- a transmission search coil for transmitting a magnetic field;
- a transmission apparatus for energising the transmission search coil with a substantially rectangular voltage producing a pulsed waveform;
- a receive coil for detecting the changes in the surrounding magnetic field through a voltage induced across the receive coil by changes in the magnetic flux;
- a measuring means for measuring the voltage across the receive coil at 3 or more selected time intervals after the end of a transmission pulse;
- and
- a processing means for processing said voltages and altering the time intervals such that a null summation is produced for a target medium by comparing the measured voltages at given sample intervals to a power law and to an exponential law.
Dependencies are inferred from the claim text.