Abstract: A ground search metal detector with a pivotally mounted search coil that locates a stem connector at either of a storage position or an operational position. The operational position locates the connector adjacent to the central portion of the search coil to facilitate useful operational characteristics, and the storage position locates the connector adjacent to the perimeter edge to facilitate compact storage of the metal detector by pivoting the stem to overlap the search coil.

Abstract: A ground search metal detector with a pivotally mounted search coil that locates a stem connector at either of a storage position or an operational position. The operational position locates the connector adjacent to the central portion of the search coil to facilitate useful operational characteristics, and the storage position locates the connector adjacent to the perimeter edge to facilitate compact storage of the metal detector by pivoting the stem to overlap the search coil.

Abstract: A hermetically sealed metal detector includes a plastic housing with an integrally formed diaphragm having a predetermined area and a thickness that enables vibration thereof by an internal acoustic transducer. An alert signal audibly drives the transducer in response to a metal detector circuit. The acoustic transducer is positioned to align the transducer output port adjacent to the interior surface of the diaphragm, which enables coupling of the acoustic signal through an air gap to vibrate the diaphragm. A cover is disposed about the diaphragm on the exterior of the housing. The cover has a vent formed therethrough for enabling passage of the acoustic energy to the exterior of the housing. Light and battery hermetic sealing are also presented.

Abstract: A hand-held metal detector and soil excavation device useful for locating and retrieving metallic objects concealed in soil or other materials. The device includes a housing with a hand-grip portion and an elongated probe portion. There is an excavation tool connected to the housing that is useful for moving soil to locate metallic objects that are sought. The device also includes a metal detector circuit located within the housing, that operates to generate an alert signal when the probe portion is moved into proximity of metallic objects.

Abstract: A metal detector has multiple transmit and receive coils for producing multiple detection fields. In one embodiment, a transmit coil is combined with two receive coils in a configuration that enables the detector to generate two detection fields, one being substantially narrower than the other. The transmit coil is inductively balanced with the receive coils such that the transmit coil induces minimum signals in each of the two receive coils. A metal target lying within a detection field changes the coupling between transit and receive coils and produces signals in the receive coils. The received signals are utilized to identify the target's presence within one or both of the detection fields. The use of two detection fields, substantially different in size, enables the metal detector to search over a broad area for object detection and then narrow the search to more precisely locate the detected object.

Abstract: A metal detector utilizes digital signal processing and a microprocessor to process buffers of information which is received at a periodic rate. Both high and low gain phase quadrature and in-phase signals are provided via a multiplexer to an analog-to-digital converter from a first receive antenna. A second receive antenna provides phase quadrature and in-phase signals also through the multiplexer to the analog-to-digital converter. The received signals are averaged, decimated and low pass filtered to eliminate noise and reduce the quantity of data which must be processed. A threshold (triggering) processing operation is performed to determine whether a valid target signal is present in the data. If not, no further processing is performed. The in-phase and quadrature components are processed using Fourier transforms to select a frequency band which includes the energy for the target signal. The energy in this frequency band is utilized to determine the identification of the target.

Abstract: A metal detector utilizes digital signal processing and a microprocessor to process buffers of information which is received at a periodic ram. Both high and low gain phase quadrature and in-phase signals are provided via a multiplexer to an analog-to-digital converter from a first receive antenna. A second receive antenna provides phase quadrature and in-phase signals also through the multiplexer to the analog-to-digital converter. The received signals are averaged, decimated and low pass filtered to eliminate noise and reduce the quantity of data which must be processed. A threshold (triggering) processing operation is performed to determine whether a valid target signal is present in the dam. If not, no further processing is performed. The in-phase and quadrature components are processed using Fourier transforms to select a frequency band which includes the energy for the target signal. The energy in this frequency band is utilized to determine the identification of the target.

Abstract: A metal detector is provided with circuitry for producing a plurality of vector signals derived from a target signal. Each of these vector signals corresponds to a phase characteristic of target signals. These vector signals define phase ranges which correspond to classifications of targets. Upon detection of a target signal, the metal detector generates first and second phase detected signals which in turn generate a plurality of vector signals. These vector signals are digitized and within a microprocessor a determination is made through slope analysis to determine which range includes the principal phase of the detected target signal. The vector signals which define the identified range are then utilized in algebraic calculations to define one of a plurality of subphase ranges within each range. This identified subphase range identifies a segment in a linear display which is illuminated to show the determined characteristic for the detected object.

Abstract: A hobby-style metal detector includes a two-piece stem interconnected by a hand grip and provided with an arm rest. A search coil is positioned at the lower end of the first section of the stem and an electronic housing is mounted on the first stem section near the hand grip. A metal detector circuit, a display and operator controls are provided with the electronic housing. A second housing is detachably connected to the second section of the stem in conjunction with the arm rest. The second housing contains batteries and can be detached and clipped to the operator's belt to reduce the weight carried by the operator's arm. A speaker can further be included within the second housing thereby removing additional weight from the arm carried unit. A cable is provided to extend from the second housing to the electronic package for providing the battery power to the metal detector circuit. When a speaker is provided in the second housing, a further line is provided in the cable for the detection signal.