Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
208 words
In an induction balance metal detector having a signal source supplying a reference signal for producing an electromagnetic field and a sensor responsive to said electromagnetic field for providing a signal phase shifted from the reference signal by metal in said field, phase detecting means connected to the sensor for producing a detector signal in response to metal in said field, and indicator means connected to the phase detecting means for identifying the metal as ferrous or non-ferrous, the improvement comprising signal input means connected to the phase detecting means for independently supplying the reference and sensor signals thereto with a predetermined phase difference in the absence of metal in the field, said phase detecting means including means for producing said detector signal as a function of either the reference signal or the sensor signal depending on the phase difference between and relative amplitudes of the reference and sensor signals, and means connected to the indicator means for comparing the detector signal with the reference signal to produce one of two metal identifying signals depending on the direction in which the reference and sensor signals deviate from said predetermined phase difference, said indicating means having two separate channels to which the two metal identifying signals are respectively fed.
Claim 2
Dependent Claim
208 words
In an induction balance metal detector having a signal source supplying a reference signal for producing an electromagnetic field and a sensor responsive to said electromagnetic field for providing a signal phase shifted from the reference signal by metal in said field, phase detecting means connected to the sensor for producing a detector signal in response to metal in said field, and indicator means connected to the phase detecting means for identifying the metal as ferrous or non-ferrous, the improvement comprising signal input means connected to the phase detecting means for independently supplying the reference and sensor signals thereto with a predetermined phase difference in the absence of metal in the field, said phase detecting means including means for producing said detector signal as a function of either the reference signal or the sensor signal depending on the phase difference between and relative amplitudes of the reference and sensor signals, and means connected to the indicator means for comparing the detector signal with the reference signal to produce one of two metal identifying signals depending on the direction in which the reference and sensor signals deviate from said predetermined phase difference, said indicating means having two separate channels to which the two metal identifying signals are respectively fed.
Claim 3
Dependent Claim
14 words
The detector as defined in claim 1 wherein said predetermined phase difference is 90°.
Claim 4
Dependent Claim
44 words
The improvement as defined in claim 2 wherein the detector signal is a function of the sensor signal during the presence of ferrous metal in the field and is a function of the reference signal during the presence of non-ferrous metal in the field.
Claim 5
Dependent Claim
66 words
The improvement as defined in claim 3 including feedback means connected to one of the channels of the indicating means for transmitting the metal identifying signal as a function of the sensor signal during the presence of ferrous metal in the field, and threshold control means connecting the feedback means to the sensor for modifying the sensor signal to compensate for mineralized soil in the field.
Claim 6
Dependent Claim
59 words
The improvement as defined in claim 1 including feedback means connected to one of the channels of the indicating meansfor transmitting the metal identifying signal produced during the presence of ferrous metal in the field, and threshold control means connecting the feedback means to the sensor for modifying the sensor signal to compensate for mineralized soil in the field.