Portable metal detector with enhanced and adjustable detection power

Abstract

The invention relates to a portable metal detector (20) with increased detection power achieved by adding a power converter (25). The power converter (25) is located away from the detection coil (22) and, in particular, from the device that captures electrical disturbances from the electromagnetic field produced by the transmitting coil(s) (220). This location prevents the operating frequency of the power converter (25) from interfering with the signal captured by the detection device. [Fig. 1]

Description

Title of the invention: Portable metal detector with improved and adjustable detection power technical field

[0001] The invention relates to a portable metal detector which has improved detection power and is adjustable according to the complexity of the substrates in which the searches are carried out. Previous technique

[0002] A typical metal detector comprises a magnetic search coil, also called a search coil. The search coil is mounted at the end of a shaft, which has a handle and a control box at its upper end. The control box is configured to operate the search coil, which includes an electromagnetic coil. This coil is configured to generate an electromagnetic field that interacts with metallic objects buried in a substrate such as soil. The electromagnetic field induces electric currents in these metallic objects, which then produce a signal detectable by the electromagnetic coil.

[0003] Most metal detectors include electronics for processing the signal received by the coil, which is traditionally connected to the control box. The processing electronics handle the signals received by the coil and relay them to the user by producing audible or visual signals. To improve the user's listening experience during searches, metal detectors are often equipped with headphones connected to the control box. Metal detectors are also equipped with power electronics, including coil excitation means and a battery, which are generally located inside or near the control box on the metal detector's handle.The excitation current of the transmitting coil and the electrical signals measured by the latter or by the receiving coil are then transmitted by wire between the handle where the power electronics and the processing electronics are housed and the electromagnetic coil.

[0004] The wired communication between the coil and the power electronics, and in particular the excitation means which are located here in the coil's remote control unit, involves resistance that necessitates the production of a high-voltage electrical current to power the electromagnetic coil. Indeed, the resistance of a wire is proportional to its length and inversely proportional to its diameter. Thus, a long electrical wire with a small diameter produces a high resistance. which degrades the power supply efficiency of the electromagnetic coil due to the Joule effect and requires the use of a higher capacity battery.

[0005] To improve the coil's power supply efficiency, document EP 2 910 979 describes a metal detector whose detection coil incorporates, in addition to the electromagnetic coil, the power electronics, including the coil excitation means, the signal processing electronics, the power supply battery, and also a wireless transmitter / receiver. The wireless transmitter / receiver is configured to communicate with a compatible wireless transmitter / receiver integrated into the control unit. Wireless communication with the coil's control unit allows the control unit to operate the coil and receive the signal captured by the coil. The positioning of the excitation means near the transmitting coil thus limits the Joule heating losses that would have been caused by an extension cable.

[0006] Although the power supply efficiency of the transmitting coil is improved, this configuration presents problems if one wishes to adjust the strength of the magnetic field emitted by the transmitting coil. For example, if one wishes to increase the strength of the magnetic field, it is known to initially increase the excitation current by reducing the series resistance of the coil while simultaneously reducing its inductance, but higher currents lead to significant losses and oversizing of the excitation means. The other known solution is to increase the excitation voltage. For this, a switching voltage converter in a boost converter configuration is generally used. This converter takes the battery voltage as its energy source and produces a higher output voltage.This type of converter has the advantage of offering high efficiency; however, it has the drawback of generating radiated electromagnetic noise, linked to the switching of the switching component(s) at a natural frequency. This signal noise phenomenon is all the more problematic because it is difficult to filter during the processing of the signal received by the coil. Indeed, the coil exhibits sensitivity to disturbances on the order of a few nanovolts of noise at the input.

[0007] US patent 10,809,411 describes a metal detector comprising power electronics, including coil excitation means, as well as the battery and processing electronics, housed in a compartment located in the detector shaft that carries the search coil. This compartment also includes a control unit configured to operate the power electronics and the processing electronics. The control unit further includes a wireless transmitter / receiver configured to communicate with a wireless transmitter / receiver integrated into the control box, which is located near the handle or can be placed remotely at the user's convenience, for example, in a backpack. This configuration This allows for increased battery capacity without disrupting the signal received by the coil, as the battery is located within the boom. However, the power electronics, and in particular the excitation components, are connected to the coil by a cable, which again creates significant resistance to the coil's excitation current and thus degrades efficiency. The excitation current is an alternating current that flows between the excitation components and the transmitting coil. This excitation current is generally carried by an excitation cable.

[0008] US patent 9,690,005 describes a metal detector comprising a search coil connected by wire to power electronics and processing electronics housed in a compartment within the metal detector shaft. This patent connects the processing electronics to a wireless transceiver configured to communicate with headphones equipped with a compatible wireless transceiver. While the battery is positioned within the shaft, the performance loss due to the resistance of the coil's excitation cable persists.

[0009] The invention aims to overcome all of these drawbacks. Description of the invention

[0010] The invention aims to provide a metal detector whose detection capacity is improved while limiting the losses in power supply efficiency of the electromagnetic coil.

[0011] In this context, the invention relates to a portable metal detector comprising: - a detection disc that includes one or more coils configured to emit and receive an electromagnetic field, - gripping means configured to allow gripping of the metal detector, - a rod comprising a first end which carries the detection disc and a second end opposite the first end, the second end being coupled to the gripping means of the metal detector, - a battery that is configured to deliver a battery current with a predetermined voltage value, - a power converter which is electrically connected to the battery; this power converter is configured to produce an electric current whose voltage value is modified relative to the voltage value of the current at the battery terminals; the power converter directly or indirectly supplies the first coil(s), - a control unit comprising a transmitter / receiver and a signal processing module for the signal captured by the coil(s), - a control box comprising, on the one hand, a human-machine interface and a transmitter / receiver configured to communicate with the transmitter / receiver of the control unit, in order that the power converter does not interfere with the electrical signals received by the coil(s), the power converter is located at least a minimum distance determined d from all points of the coil(s).

[0012] Adding a power converter to the power supply circuit of the transmitting coil(s) allows the voltage to be adjusted, and in particular, the voltage across said coil(s) to be increased, for example, to increase the strength of the electromagnetic field. Increasing the strength of the electromagnetic field enhances the detection capabilities of the metal detector. Positioning the power converter at a minimum distance d from all points of the coil(s) prevents the power converter's operating frequencies from interfering with the receiving function of the coil(s), that is, the signals received by the coil(s) that correspond to electrical disturbances in the electromagnetic field emitted by the coil(s) in transmitting mode. These electrical disturbances are generally produced by metallic objects.

[0013] Indeed, the coil(s) in receiver mode exhibit a high sensitivity to disturbances on the order of a few nanovolts of input noise. This sensitivity improves detection but makes the coil(s) in receiver mode more susceptible to disturbances. Furthermore, the use of a power converter makes it possible to increase the voltage while maintaining a compact battery that can be easily integrated into the tubular structure of the shaft or the detection coil. Using a battery composed of several cells in series would also require a complicated method for recharging and balancing the cells.

[0014] In the remainder of this document, "capturing a signal" means that the coil(s) in receiving mode capture the surrounding electromagnetic field of the disk and convert it into an electrical voltage. This electromagnetic field includes all magnetic fields present in the environment, and in particular that generated by the coil(s) in transmitting mode, as well as the disturbances created by metallic bodies buried in the substrate / soil where the research is being conducted.

[0015] In the remainder of this document, the transmitting coil refers to a coil that operates only in transmit mode or a coil that is in transmit mode transiently. Similarly, the receiving coil refers to a coil that operates only in receive mode or a coil that is in receive mode transiently.

[0016] [Battery and power converter]

[0017] In some embodiments, the battery can also be located at least a minimum distance d from all points of the coil(s). Relocating the battery helps to limit interference with the electromagnetic field signal received by the receiving coil(s). Indeed, the metal mass of the battery produces interference with the electromagnetic field received by the receiving coil(s) when the battery is located near them. Furthermore, relocating the battery allows the metal detector to be equipped with a high-capacity battery. Whereas such a battery near the receiving coil(s) would cause problems related to its size and interference with the signal it produces.

[0018] In some embodiments, the detection disc can be oriented in at least one direction relative to the rod, the power converter being offset at least a predetermined minimum distance d from all points of the coil(s), regardless of the orientation of the detection disc relative to the rod. This prevents interference with the signal received by the receiving coil(s), regardless of the orientation of the detection disc. It should be noted that the articulation between the detection disc and the bottom of the rod can comprise a single axis, for example a rocker joint, or several axes, such as a ball joint.

[0019] In embodiments, the battery and the power converter may be positioned at least at a minimum distance d of 10 cm or more, preferably 15 cm or more. Such a spacing prevents the generation of electromagnetic interference near the receiving coil(s) and thus avoids noise in the received signal.

[0020] In embodiments wherein the battery and power converter can be arranged in a housing mounted at least at the specified minimum distance d on or within the metal detector shaft. Such an arrangement makes it possible to find a compromise between increasing detection power and limiting interference with the signal received by the receiving coil(s).

[0021] In an alternative embodiment, the battery and power converter can be housed in a compartment coupled to the control unit, with an electrical cable connecting the power converter to the coil(s) located in the detection coil. This embodiment makes it possible to increase the working power of the transmitting coil while maintaining a conventional mechanical structure for the metal detector.

[0022] In some embodiments, the control unit may also be located remotely; for example, the control unit may be located remotely from the detection disc. According to a particular configuration, the control unit may be integrated into the housing which contains the battery and the power converter.

[0023] In some embodiments, the control unit is configured to determine a voltage setpoint that the power converter must supply to the coil(s), the control unit being electrically connected to the power converter. This feature allows the user, via the control box communicating with the control unit, to adjust the voltage setpoint of the electrical current supplied by the power converter. The intensity of the electromagnetic field can be adjusted according to the complexity of the soil.

[0024] In some embodiments, the handheld metal detector may include filtering means disposed between the power converter and the coil(s). The filtering means are configured to supply a direct current with a linear and regulated voltage. The filtering means smooth the voltage supplied to the transmitting coil and thus improve the quality of the electromagnetic field emitted by the transmitting coil. According to a particular embodiment, the filtering means may be passive, for example, inductive, capacitive, or resistive, or a combination of the three.

[0025] In some embodiments, the handheld metal detector may include a voltage driver configured to determine the setpoint voltage of the supply current produced by the power converter. The voltage driver allows modulation of the voltage setpoint applied to the terminals of the coil(s) and thus varies the detection power. This can be useful for adapting the intensity of the electromagnetic field emitted by the coil according to the complexity of the substrate in which the user is searching for metallic targets. According to a particular embodiment, the voltage driver may be a digital potentiometer controlled by a digital setpoint from a dedicated control unit, the control unit of the control box, or the control unit present in the detection coil.

[0026] In some embodiments, the power converter may include a voltage booster and / or a voltage step-down converter. To increase the detection power, it is useful to increase the supply voltage of the excitation means. However, it may also be useful to reduce the detection power when the detection substrate exhibits one or more significant ground effects, such as the magnetic effect present in mineralized soils, or the conductive effect observed in salt water, for example. The electrical properties of the soil can vary depending on its mineral composition, moisture content, and other factors. These variations can influence how electromagnetic signals are transmitted and received by the metal detector, which can affect the detection accuracy. Furthermore, soil or substrate mineralization refers to soils or substrates that They are loaded with minerals that can affect the detection of metallic objects. Indeed, certain minerals, such as iron and magnetite, react to magnetic excitation by producing their own magnetic field, which dazzles the receiver of the metal detector, thus complicating the detection of metallic targets.

[0027] Thus, in the case of a ground effect, which can occur in mineralized soil or substrate, the intensity of the field reflected by this substrate can lead to saturation of the amplification and filtering chain, preventing any detection. The voltage reducer allows the voltage to be adjusted to a lower value in order to overcome this saturation state of the amplification chain. In another application, lowering the voltage can also increase the battery life of the first coil(s). Conversely, raising the voltage can increase the detection range. Furthermore, increasing the voltage, and therefore the intensity of the electromagnetic search field, increases the strength of the signal received by metallic targets and thus improves immunity to external electromagnetic interference.

[0028] In a preferred embodiment, the power converter may include a voltage booster and a voltage step-down converter, or a combination of both. The power of the metal detector can thus be adjusted according to the complexity of the substrate in which the searches are conducted.

[0029] In embodiments, the handheld metal detector may include a remote cord which connects, directly or indirectly, the power converter to the coil(s).

[0030] [Excitation means - power circuit]

[0031] In some embodiments, the handheld metal detector may include electrical excitation means that are connected directly or indirectly to the power converter and are configured to transform the electrical current supplied by the power converter into alternating current to power the terminals of the coil(s). In particular, the excitation means are arranged in the detection disc near the coil(s). The excitation means are integrated into the power circuit that is configured to excite the transmitting coil(s).

[0032] In some embodiments, the excitation means are arranged at a distance L from the terminals of the coil(s). Preferably, the distance L is less than or equal to the diameter of the detection disk; in particular, the distance L is less than or equal to 30 cm, and preferably, the distance L is less than or equal to 10 cm. To improve the excitation efficiency of the transmitting coil(s) and limit Joule heating losses, the excitation means are arranged as close as possible to the terminals of the transmitting coil(s). Indeed, the short conductor length between the means The excitation and the emitting coil(s) allows the value of the equivalent series resistance to be reduced accordingly, and consequently the losses due to the Joule effect caused by the high currents exchanged between the emitting coil and the excitation means.

[0033] In some embodiments, the excitation means may include a switching amplifier comprising transistors configured to convert the fixed excitation voltage into an alternating voltage across the transmitting coil(s), which produces a current varying alternately within the transmitting coil(s), thereby inducing the search electromagnetic field. The switching amplifier may be of the H-bridge type with power transistors driven by the control unit. Such excitation means are found, for example, in frequency detectors.

[0034] In some embodiments, the excitation means may include a linear amplifier coupled to an oscillator that supplies the coil(s) with an alternating current, inducing an electromagnetic detection field. The linear amplifier has the advantage of not creating electromagnetic disturbances visible to the receiving coil(s). These excitation means are found, for example, in so-called beat frequency detectors or "BFO Detectors."

[0035] In some embodiments, the excitation means may include a pulse generator architecture, which may be based on a transistor, for example. These excitation means are found, for example, in time-domain metal detectors, such as pulse induction metal detectors.

[0036] In some embodiments, the excitation means may include one or more decoupling capacitors configured to smooth the excitation voltage by storing and exchanging the electrical current accumulated in the coil(s) at each reversal of the excitation current in said coil(s). Thanks to their low series resistance, the decoupling capacitors reduce electrical energy losses during the alternation of the excitation current in the transmitting coil(s).

[0037] In embodiments, the control unit is configured, on the one hand, to determine the frequency composition of the signal emitted by the coil(s) through the control of the excitation means and in particular the inversion frequency of the excitation current, and on the other hand, the supply voltage that the power converter provides to the excitation means.

[0038] [Signal processing electronics]

[0039] In some embodiments, the control unit may include a signal processing module configured to demodulate and filter the analog signal measured by the sensing device and to detect variations in the analog signal. The detector The metal detector may also include an amplification and filtering chain for the measured signals and an analog-to-digital converter configured to transform the measured signals in analog form into digital signals. These components are part of the analog signal processing electronics for the signal measured by the detector.

[0040] In some embodiments, the analog-to-digital converter and the amplification and filtering chain are located within the detection disc. The advantage of positioning the analog processing chain as close as possible to the sensing element is to limit the pickup of external interference or interference present within the metal detector system. Once converted into digital signals, the signal can then be transmitted without loss of quality to the various processing and detection components, as well as to the human-machine interface (HMI).

[0041] Alternatively, pre-amplification and signal conditioning can be carried out as close as possible to the capture device in order to increase the robustness of the captured signal so as to transport it without loss to the rest of the processing and detection chain located at a distance such as an analog-to-digital converter or analog processing and detection means.

[0042] In some embodiments, the signal from the sensing device is conditioned and then processed in an analog manner without using an analog-to-digital converter. This embodiment is used, for example, in older generation metal detectors that do not have digital electronics, such as certain beat frequency metal detectors, certain "Time Domain" detectors, or certain "Frequency Detectors".

[0043] [Coils]

[0044] In embodiments, the detection disk may include at least one first emitting coil configured to emit a magnetic field and at least a second coil configured to capture electrical disturbances from said electromagnetic field.

[0045] In some embodiments, the detection disk may include coils that cross and overlap, at least partially, within the detection disk. This configuration makes it possible to cancel the component of the field emitted by the transmitting coil by opposing the magnetic fluxes within the receiving coil.

[0046] In some embodiments, the coil(s) have a transmission mode and a reception mode, the coil(s) operating alternately in transmission and reception mode. This may be the case, in particular, for pulse induction metal detectors.

[0047] [Communication between the control box and the control unit and accessories]

[0048] In some embodiments, the transmitters / receivers of the control box and The control unit's communication protocols can be wireless. Specifically, wireless transmitters / receivers can operate using radio, optical, or acoustic communication protocols. Preferably, the communication protocol between the control unit and the control box is radio.

[0049] In alternative embodiments, the transmitters / receivers of the control box and the control unit may be wired, with a cable extending between the control box and the control unit to allow the transmitters / receivers to communicate.

[0050] In some embodiments, the metal detector may include human-machine interface accessories such as headphones, and accessories that communicate with the control unit via a communication protocol, preferably wireless. In particular, the communication protocol between the accessories and the control unit may differ from the communication protocol established between the control unit and the control system. Naturally, the accessories and the control unit each incorporate a transmitter / receiver that may be dedicated to this communication.

[0051] In other embodiments, the communication protocol between the accessories and the control box can be wired and use, for example, a USB type connection or jack plug or any other means of connection with the audio headset. Brief description of the drawings

[0052] Other features and advantages of the invention will become apparent from the following description. This description is purely illustrative and should be read in conjunction with the accompanying drawings, in which:

[0053] [Fig. 1] is a schematic representation of a portable metal detector conforming to an embodiment of the invention.

[0054] [Fig.2] is a schematic representation of a synoptic architecture of the electronic elements that make up a portable metal detector conforming to an embodiment of the invention.

[0055] Figs. 3, 4 and 5 are schematic representations of conforming handheld metal detectors of the invention, each of which sets out a distinct embodiment of the invention.

[0056] [Fig.6] is a synoptic diagram of the elements that make up the battery pack of a metal detector conforming to an embodiment of the invention.

[0057] [Fig.7] is a synoptic diagram of the elements that make up the excitation circuit of the first coil of a conforming metal detector of an embodiment of the invention.

[0058] [Fig-8] is a more detailed synoptic diagram of an embodiment of [Fig.7]. Description of the implementation methods

[0059] With reference to Figures 1 to 8, the invention relates to a portable metal detector 20. In this document, the term portable means that the metal detector is designed to be carried by the user, for example, by means of a shoulder strap that is attached to the metal detector.

[0060] To facilitate gripping and handling, the metal detector 20 includes gripping means 21. The user can thus use the gripping means 21 to orient the metal detector towards a target, which is generally located on the ground. According to the embodiment illustrated in [Fig. 1], the gripping means comprise a handle 210 surmounted by an extension 211 configured to provide forearm support. The extension 211 provides user comfort.

[0061] The metal detector 20 includes a detection disc 22 which includes at least a first coil 220 configured to emit an electromagnetic field.

[0062] According to one embodiment, the detection disc may also include at least one second coil 221, called the receiving coil, configured to capture the emitted magnetic field and electrical disturbances from said field. According to this embodiment, the metal detector may be of the "Frequency detector" type, also called a beat frequency detector; that is, the first coil 220 generates a continuous electromagnetic field, and the receiving coil 221 captures the variations in the field induced by the first coil in order to detect metallic targets buried in the ground. According to this embodiment, the first emitting coil 220 and the second receiving coil 221 may intersect and overlap within the detection disc 22.

[0063] The invention also relates to pulse induction metal detectors or "Time Domain Detectors" which perform a temporal analysis of the impulse response of the environment, for example, the ground, to detect buried metallic targets. This type of detector may comprise a first coil and a receiving coil, or alternatively, a coil alternately fulfilling a transmitting and receiving function. According to this embodiment, the coil(s) 220 operate alternately in transmitting and receiving mode.

[0064] In the embodiment illustrated in [Fig.2], the metal detector 20 comprises a transmitting coil 220 and a receiving coil 221. In this diagram, the coils 220, 221 are symbolized by a helical winding.

[0065] As illustrated in particular in [Fig. 1], the detection disk 22 comprises an annular or elliptical element 222. Here, the element 222 includes a notch which It fits within the circumference. Here, the coil(s) 220, 221 are provided within the element 222. The element 222 is connected to the metal detector 20 by branches 223 that couple it to the bottom of a shaft 23 of the metal detector 20. Indeed, the metal detector 20 includes a shaft 23 that can be telescopic and comprise two sections movable relative to each other, as illustrated in [Fig. 1]. The shaft 23 has a first end 230, called the bottom of the shaft, and a second end 231, called the top of the shaft, which is opposite the first end 230.

[0066] In this example, the first end 230 carries the detection disc 22, while the second end is coupled to the handle 210 of the metal detector 20. In one embodiment, the detection disc 22 can be oriented in at least one direction relative to the shaft 23. In particular, the metal detector 20 may include a joint 232 for coupling the first end 230 to the detection disc 22. This joint 232 allows the detection disc 22 to be oriented at least at a defined angle α between the plane of the detection disc 22 and the longitudinal axis of the shaft 23, as illustrated in [Fig. 1]. When the metal detector 20 is in its operating configuration, the angle α can be between 0 and 190°. When the metal detector is not in use, the detection disc 22 can be folded against the shaft 23 for compactness.

[0067] According to one embodiment, the metal detector 20 may include a battery pack 24 as illustrated in particular in [Fig. 6]. The battery pack 24 includes at least one battery 240 for supplying the transmitting coil 220 with electric current. The battery 240 may include one or more accumulators that may be connected in series or in parallel, or in a combination of both. The battery pack 24 may include a protection circuit with, for example, short-circuit and overvoltage protection features. The battery 240 is factory-configured to deliver a battery current 244 with a predetermined voltage, which may, for example, be between 3 and 13 volts. In the embodiment of [Fig. 6], the battery pack 24 includes a connector 241 that connects the battery 24, directly or indirectly, to the transmitting coil 220.Connector 241 is also connected to a charger 242, which may be equipped with a charge indicator light-emitting diode (LED). The battery pack 24 further includes a charging connector 243, which is configured to be connected to an electrical power source. Connector 243 may, for example, include a male or female USB-B or USB-C connector. Connector 243 may also include two exposed contacts, positive and negative, in conjunction with spring-loaded contacts positioned on a charging cable that has a standard USB-A connector at the other end, compatible with +5V AC power supplies.

[0068] Of course, any other connector capable of ensuring the transfer of electrical current can be used to constitute the charging connector 243.

[0069] According to the invention, the metal detector 20 comprises a power converter 25 which can be integrated into the battery pack 24 in certain embodiments. The power converter 25 is electrically connected to the battery 240. The power converter 25 is configured to produce an electric current whose voltage value is modified relative to the voltage value of the current at the terminals of the battery 244. The power converter 25 supplies the coil 220 directly or indirectly.

[0070] According to a preferred embodiment, the power converter is configured to supply an electric current with a voltage higher than the voltage across the battery terminals. The power converter 25 can be configured, for example, to double the voltage of the battery current 244. Thus, when a battery delivers a current of 5 volts, the power converter 25 increases the voltage of the direct or indirect supply current to the coil 220 to 10 volts.

[0071] According to one embodiment, the power converter 25 may include a voltage booster. More particularly, the voltage booster may be a chopper which may include several possible parallel chopper (or "boost chopper") topologies, or a voltage booster with switched capacitors.

[0072] According to another embodiment, the power converter 25 may include a step-down converter in the case where the voltage across the battery terminals is higher than the voltage required to power the emitter coil. According to this embodiment, the power converter 25 may include a series chopper (or "buck chopper") in a "forward" topology, for example, or linear regulators of the LDO ("low dropout regulator") type.

[0073] According to another embodiment, in the case where the input voltage of the power converter 25 is unknown or changing, such as in the case of a discharging battery, the power converter 25 can combine both step-down and step-up voltage modes. For this purpose, the power converter 25 can include a series-parallel chopper topology (e.g., a buck-boost chopper or half-bridge converter), in a flyback topology.

[0074] Figure 6 illustrates an embodiment of the invention in which the battery 240 is coupled to a power converter 25 to supply the coil 220 with a supply current having a higher voltage value. According to one embodiment, the power converter 25 may comprise a DC-DC voltage converter, that is, a converter configured to receive a direct current, increase its voltage. voltage and output a direct current with a voltage higher than the voltage of the current it receives. Of course, the power converter 25 may include other electronic components of the type that are capable of increasing the voltage value of an electric current.

[0075] According to an embodiment illustrated in [Fig. 6], the metal detector 20 may include filtering means 250 arranged between the power converter 25 and the coil 220. The filtering means 250 are configured to supply a direct current with a linear voltage value. In this example, the filtering means 250 are passive, for example, of the inductive, capacitive, or resistive type, or a combination of the three.

[0076] According to another embodiment, the metal detector 20 may include a voltage driver 251 configured to determine the setpoint voltage of the supply current produced by the power converter 25. The voltage driver 251 may include a potentiometer controlled by a digital or analog control. In particular, the potentiometer acts resistively on the feedback loop of the power converter 25, thereby modifying the regulated voltage.

[0077] The voltage driver 251 may also include a transistor, for example of the MOSFET or bipolar type, or a mechanical / electronic contact. The transistor is controlled digitally or linearly to adjust one of the parameters of the current, voltage, or frequency regulation feedback of the power converter 25.

[0078] The voltage driver 251 thus acts on the modification of the chopping signal (frequency, duty cycle, complex harmonic mixture) of the power converter 25 to control the voltage setpoint.

[0079] Some SoC (system on chip) type power converters can incorporate a voltage driver for their setpoint value in analog or digital form.

[0080] In this example, the voltage driver 251 is connected to a control unit 26. Indeed, as illustrated in [Fig.2], the metal detector 20 includes a control unit 26 which is configured in particular to determine the voltage setpoint to be supplied to the coil 220. In the example of [Fig.6], communication circuits 252, in particular of the bus type, connect the control unit 26 to the voltage driver 251.

[0081] According to the invention, the control unit 26 is controlled by a control box 27 which includes a human-machine interface 270 allowing the user of the metal detector 20 to modulate the voltage setpoint of the power converter 25. The human-machine interface 270 can be integrated into the control box 27 or remotely in a smartphone via a dedicated application.

[0082] Adjusting the voltage setpoint allows the power of the ma field to be adjusted The magnetic field emitted by the metal detector adapts to the search environment to maintain the best signal-to-noise ratio without saturating the measurement chain. Indeed, certain environments, such as mineralized soils or soils polluted by large or multiple unwanted targets, react to magnetic excitation by reflecting a greater amount of energy back to the detector at specific frequencies. This energy saturation can saturate the captured signal, potentially leading to saturation of the amplifiers in the measurement chain and consequently producing non-linearities in the signal. These signal non-linearities generate noise and false detections.

[0083] In the case of weakly mineralized ground, it may be desirable to increase the useful signal of the targets sought in order to increase the detection depth in the ground or to cover the surrounding electromagnetic pollution; the increase in voltage and therefore in the magnetic field is then desirable.

[0084] Increasing the voltage and therefore increasing the intensity of the electromagnetic search field makes it possible to increase the strength of the signal received by the metallic targets and thus improves immunity to external electromagnetic disturbances, which may be desirable for example in the case of using the metal detector in an environment polluted by electromagnetic fields from rotating machines such as a heat pump, or a photovoltaic power plant inverter.

[0085] The ability to adjust the voltage setpoint can also allow a soft start of the power converter 25 by gradually increasing the power of the magnetic field, so as to preserve the electronics from malfunction or damage.

[0086] Finally, adjusting the voltage setpoint allows the user to choose a compromise between the advantages of higher power and battery life. In certain circumstances, the user may prefer to conserve energy to extend the search time; lowering the voltage setpoint of the power converter 25 is then desirable.

[0087] According to an embodiment illustrated in [Fig. 6], the metal detector 20 may include a switch 253 that manages the battery current supply 244 to the power converter 25. The switch 253 is controlled by the control unit 26 through communication circuits 252. According to one embodiment, the switch 253 may be configured to put the power converter into standby mode when the control unit 26 commands it, for example, when the user wishes to temporarily stop detection or when the metal detector 20 is switched off.

[0088] According to another embodiment, the switch 253 can be configured to pass A standby mode is activated when the extension cable 254, which connects the battery pack 25 to the control unit 26, is disconnected from its interface connector 255. This occurs whether the disconnection of the extension cable 254 is intentional or unintentional. The interface connector 255 connects, via the extension cable 254, the communication circuits 252 to the control unit, and the power converter 25 and the coil 220. The extension cable 254 may be a wired type with one or more conductors, each composed of one or more strands. The conductor core is insulated from the other conductors by an insulating sheath. An additional outer sheath may bundle and protect all the conductors of the cable. Some conductors may be twisted or braided together, while other conductors may have electrical shielding.

[0089] According to this embodiment, the remote control cable 254 electronically connects the control unit 26 to the power converter 25. In order to modulate the voltage setpoint of the power converter 25, the control unit 26 can be configured to communicate with the control box 27. For this purpose, the control unit 26 includes a first transmitter / receiver 260 which is configured to communicate with a second transmitter / receiver 271 integrated into the control box 27. This communication channel also allows the transfer of data relating to the analog signal received by the receiving coil 221.

[0090] According to one embodiment, the control unit 26 comprises a signal processing module 261 for the signal received by the sensing element. The signal processing module 261 is adapted according to the configuration of the coils 220, 221 and the type of metal detector 20 as described above. The processing module 261 is configured to demodulate, filter the signal, and detect variations in the signal.

[0091] According to one embodiment, the processing module 261 can be implemented in an analog manner. In this case, the processing module 261 comprises filtering and detection means in the form of analog electronic circuits, for example rectifiers, comparators, filters, and logic circuits, for example logic gates, flip-flops.

[0092] According to another embodiment, the processing module 261 can be implemented digitally. In this case, the processing module 261 can be integrated into the control unit 26 or comprise a dedicated circuit which can be of the microcontroller, microprocessor, PSD (digital signal processor), or programmable logic circuit type (e.g., FPGA).

[0093] According to the embodiment illustrated in [Fig. 2], the metal detector 20 may include an amplification and filtering chain 200 for the analog signals received by the receiving coil(s). The amplification and filtering chain 200 receives the analog signals received by the receiving coil(s), amplifies the The signal processor performs an initial noise filter and then transmits the signals to the processing module 261 of the control unit 26. For example, the amplification and filtering chain 200 may include passive filters composed of inductive, resistive, and capacitive elements. The amplification and filtering chain 200 may also include low-noise or high-noise amplifiers with fixed or variable gain and a bandwidth restricted to the desired signal. The amplification and filtering chain 200 may include other components such as high-order active filtering cells, low-noise amplifiers, and means for controlling gain and bandwidth.

[0094] According to another embodiment, the metal detector 20 may include an analog-to-digital converter 201 configured to transform the analog signals received by the receiving coil(s) into digital signals. The analog-to-digital converter 201 may be interposed between the amplification and filtering chain 200 and the processing module 261 as illustrated in [Fig. 2].

[0095] According to the embodiment of [Fig. 2], the analog-to-digital converter 201 and the amplification and filtering chain 200 are arranged in the detection disk 22. However, according to an alternative embodiment, the signal captured by the receiving coil(s) can be relayed to a terminal, located away from the detection disk 22, which may include the amplification and filtering chain 200, the analog-to-digital converter 201, and the processing module 261. This remote terminal may be the control unit 27. In this particular embodiment, initial signal conditioning is performed to make the signals more robust for transmission to a remote terminal. This initial conditioning may include an amplification and filtering stage, and to enable transmission via an electrical connection, a differential signal conversion for improved immunity to external interference.Or alternatively, to allow the transmission of signals via a conducted electrical, radio, optical or sound link: a transposition of the signals to carrier frequencies by modulation.

[0096] The inventors realized that the addition of the power converter 25 is a source of disturbance to the captured signal; indeed, the power converter 25 generally includes a converter whose chopping clock and operating frequency generate harmonics that are very difficult to filter if the power converter 25 is located in the direct vicinity of the receiving coil(s) and to a lesser extent in the vicinity of the amplification and filtering chain 200 and the digital converter 201. These elements are very sensitive to electromagnetic fields and the power converter 25 generates noise over a wide frequency band that is difficult to filter.

[0097] Therefore, according to the invention, the power converter 25 is located at least a minimum distance d from all points of the receiving coil(s). Preferably, and as illustrated in [Fig. 1], the battery pack 24, which incorporates the power converter 25 and the battery 241, is located at least a minimum distance d from all points of the receiving coil(s).

[0098] According to the embodiment, in which the detection disc 22 is orientable relative to the rod 23 in at least one direction, the power converter 25 and preferably also the battery 241 are located at least at a minimum determined distance d from all points of the receiving coil(s) regardless of the orientation of the detection disc 22 relative to the rod 23. The minimum distance d is determined so that, regardless of the orientation of the detection disc, the disturbances produced in particular by the power converter 25 are sufficiently far away, in particular, from the receiving coil(s) so as not to interfere with the received signal.

[0099] According to one embodiment, the power converter 25 is positioned at a minimum distance d greater than or equal to 10 cm from all points of the receiving coil(s), preferably, the minimum distance d is greater than or equal to 15 cm. In practice, the battery 241 can also be positioned at least at this minimum distance when, in particular, according to one embodiment, the power converter 25 is located in the battery pack 24.

[0100] In one embodiment, the metal detector 20 comprises electrical excitation means 28 configured to excite the transmitting coil 220. The excitation means 28 are connected directly or indirectly to the power converter 25. In particular, in the example of [Fig. 2], the excitation means 28 are connected to the power converter 25 via the extension cable 254, which connects the interface connector 255 of the battery pack 24 to the interface connector 223 of the detection disc 22. In this embodiment, the control unit 26 may include a signal driver 262 configured to actuate the excitation means 28 so as to emit an electromagnetic field determined by the control box 27. In one embodiment, the user can modify the electromagnetic field emitted by the coil 220 via the human-machine interface 270 of the control box. 27.

[0101] According to a preferred embodiment, the excitation means 28 are arranged at a distance L from the terminals of the transmitting coil 220, preferably, the distance L can be less than or equal to the diameter of the detection disk 22. In particular, the distance L can be less than or equal to 30 cm, and preferably, the distance L is less than or equal to 10 cm.

[0102] According to an embodiment illustrated in particular in Figures 2 and 3, the means Excitation elements 28 are arranged in the detection disc 22 at a distance L proximal to the transmitting coil(s) 220. According to the preferred embodiment of [Fig. 3], the battery 241 and the power converter 25 are arranged in a housing 245 which is mounted at least at the minimum predetermined distance d in the shaft 23 of the metal detector 20. Alternatively, the housing 245 can be arranged on the shaft 23 in a projecting manner and integral with the latter. This embodiment is illustrated in [Fig. 3], in which the position of the housing 245 is located in the lower part of the shaft 23 below the junction 232 between the two arms of the shaft 23. According to this configuration, the extension cord 254 schematically shown in [Fig. 6] connects the power converter 25 to the coil 220 and to the counter unit 26 as previously described.

[0103] The extension cord 254 can be arranged in the lower tube of the rod 23 or extend outside the rod 23 between the power converter 25 and the interface connector 223 of the detection disc 22. The extension cord 254 can be straight or spirally wound. According to the embodiment of [Fig. 2], the interface connector 223 connects, in particular, the power converter 25 to the coil 220 via the excitation means 28.

[0104] According to an alternative embodiment illustrated in [Fig. 4], the electrical excitation means 28 and the battery pack 24 are arranged in the detection disc 22, while the power converter 25 is located at least a minimum distance d from all points of the receiving coil(s). According to another alternative embodiment illustrated in [Fig. 5], the excitation means 28 are arranged in the detection disc 22 near the transmitting coil(s) 220. The battery pack 24, which also includes the power converter 25, is arranged in a compartment in the control box 27, which is located at the second end 231 of the rod 23. The extension cord 254 then connects the power converter 25 to the excitation means 28 located in the detection disc 22.

[0105] Alternatively, the excitation means 28 can be arranged in the housing 245; however, such a configuration requires the use of a connector to link them to the terminals of the coil(s) 220, and this connector produces a detrimental loss of efficiency. Conversely, when the excitation means 28 are arranged in the detection disk 22, it is possible to solder them to the same electronic circuit as the terminals of the coil(s).

[0106] According to the embodiment illustrated in [Fig. 7], the extension cord 254 transmits the supply current produced by the power converter 25 to the excitation means 28, which are controlled by the control unit 26. The excitation means 28 correspond to a power converter configured to convert the DC supply current provided by the power converter 25 into AC current alternative to excite the transmitting coil(s) 220 and induce a search electromagnetic field. The control unit 26 can act on the intensity and / or the frequency composition and energy distribution in the spectrum of the electromagnetic field induced by the coil(s) 220. As described previously, the control unit 26 can also adjust the voltage of the supply current provided by the power converter 25 through the remote cable 254 and the communication circuits 252, which allow it to act on the voltage driver 251.

[0107] Figure 8 describes a particular embodiment of the excitation means 28. According to this embodiment, the excitation means 28 comprise an amplifier 281 which is configured to excite, from the supply current coming from the remote cord 254, the emitter coil(s) 220 according to an alternating current described by excitation signals ordered by the control unit 26. The amplifier 281 is directly connected to the emitter coil(s) 220.

[0108] The amplifier 281 can be of several types. In one embodiment, the amplifier 281 is a switching amplifier, which is a chopper power converter of the inverter type. The switching amplifier comprises transistors configured to cut the supply voltage so as to power the emitter coil(s) 220 with an alternating excitation current that induces the electromagnetic detection field. The switching amplifier can be implemented as a full H-bridge, a half-bridge, or a multilevel converter.

[0109] According to an alternative embodiment, the amplifier 281 is of the linear amplifier type driven by an analog signal or coupled to an oscillator to produce an excitation signal at the self-tuning frequency (natural resonance) of the transmitting coil 220. This combination makes it possible to power the coil(s) 220, for example, in the context of a frequency beat metal detector.

[0110] According to the embodiment illustrated in [Fig. 8], the excitation means 28 comprise a decoupling capacitor 282. In this example, the decoupling capacitor 282 is interposed between the amplifier 281 and the connector 280. The decoupling capacitor 282 is configured to smooth the supply voltage by storing and exchanging the electrical current accumulated in the coil(s) 220 at each reversal of the excitation current of the coil(s) 220. The frequency of reversal of the excitation current of the transmitting coil(s) 220 is controlled by the control unit 26 and can be between 1 kHz and 200 kHz.

[0111] Figures 3 to 5 illustrate different embodiments of the arrangement of the components comprising the metal detector 20. In these embodiments, the control unit 26 is located either in the detection disc 22. However, it is also possible to locate the control unit 26 either in the control box 27, which is located at the second end 231 of the shaft 23, or in the housing 245 which includes the battery pack 24. Thus, according to one embodiment, the control unit 26 can be disposed at least at the determined distance d from the receiving coil(s).

[0112] When the control unit 26 is located remotely from the power converter 25, the remote control cable 254 connects these two components. The remote control cable 254 also connects the power converter 25 to the excitation means 28 when these two components are located remotely from each other. Finally, in one embodiment, where the excitation means 28 are located remotely from the detection disk 22 and therefore from the transmitting coil(s) 220, the metal detector may include another cable to transmit the alternating excitation current from the terminals of the coil(s) 220.

[0113] According to a preferred embodiment, the transmitter / receiver 271 of the control box 27 and the transmitter / receiver 260 of the control unit 26 are wireless and configured to communicate with each other according to a predetermined communication protocol 273. At least three alternatives exist with regard to the type of wireless communication protocol 273; the wireless communication protocol may be radio, optical, or acoustic.

[0114] According to another embodiment, the transmitter / receiver 271 of the control box 27 and the transmitter / receiver 260 of the control unit 26 are wired. In this configuration, a cable extends between the control box 27 and the control unit 26 to allow the transmitters / receivers to communicate. As shown in Figures 3 to 5, the communication protocol 273 can be a wire that runs along the rod 23 or is integrated inside the rod 23.

[0115] It should be noted that the control unit 27 can be associated with a headset 272 as illustrated in Figures 3 to 5, but also with other accessories such as tablets, smartphones, etc. Communication between the control unit 27 and the headset 272 or other accessories can be wired or wireless, using a near-field communication protocol such as a specific radio protocol, Bluetooth, Wi-Fi, etc.

[0116] Figure 3 illustrates a preferred embodiment in which the control unit 26 and the excitation means are located in the detection disc 22, while the battery 241 and the power converter 25 are positioned at a distance d from the receiving coil(s). In particular, the power converter 25 and the battery 241 are housed in a compartment 245 located in or on the rod 23 at the minimum distance d from the receiving coil(s). According to this preferred embodiment, the control unit 26 communicates with the control box 27 using a wireless communication protocol 273, specifically a radio protocol. Accessories such as the headset 272 are preferably connected wirelessly to the control boxes 27 using a different communication protocol. of the one that is used between the control unit 26 and the control box 27.

Claims

Demands

1. A portable metal detector (20) comprising: - a detection disc (22) having one or more coils (220, 221) configured to emit and receive an electromagnetic field, - gripping means (21) configured to allow gripping of the metal detector (20), - a shaft (23) having a first end (230) carrying the detection disc (22) and a second end (231) opposite the first end (230), the second end (231) being coupled to the gripping means (21) of the metal detector (20), - a battery (241) configured to deliver a battery current having a predetermined voltage, - a power converter (25) electrically connected to the battery (241),The power converter (25) is configured to produce an electric current whose voltage value is modified relative to the voltage value of the current at the battery terminals, the power converter (25) directly or indirectly supplying the first coil(s) (220), - a control unit (26) comprising a transmitter / receiver (260) and a signal processing module (261) receiving the signal from the coil(s) (220, 221), - a control box (27) comprising, on the one hand, a human-machine interface (270) and a transmitter / receiver (271) configured to communicate with the transmitter / receiver (260) of the control unit (26), so that the power converter (25) does not interfere with the electrical signals received by the coil(s) (220, 221), the power converter (25) is located at least a minimum distance d from all points of the coil(s) (220, 221).

2. A portable metal detector (20) according to claim 1, wherein the battery (241) is located at least at a minimum determined distance d from all points of the coil(s) (220, 221).

3. A portable metal detector (20) according to claim 2, wherein the battery and the power converter are disposed at least at a minimum distance d which is greater than or equal to 10 cm, preferably the minimum distance d is greater than or equal to 15 cm.

4. A handheld metal detector (20) according to any one of claims 2 and 3, wherein the battery (241) and the power converter (25) are arranged in a housing (245) which is mounted at least at the minimum distance d on or in the shaft (23) of the metal detector (20).

5. A portable metal detector (20) according to any one of claims 1 to 3, wherein the battery (241) and the power converter (25) are arranged in a housing which is coupled to the control box (27), an electrical cable connecting the power converter (25) to the coil(s) (220, 221) which are located in the detection disc (22).

6. A portable metal detector (20) according to any one of claims 1 to 5, wherein the detection disc (22) is orientable in at least one direction relative to the shaft (23), the power converter (25) is located at least at a minimum determined distance d from all points of the sensing element regardless of the orientation of the detection disc (22) relative to the shaft (23).

7. A portable metal detector (20) according to claim 4, wherein the control unit (26) is located away from the detection disc (22), preferably the control unit (26) is located away in the housing (244).

8. A handheld metal detector (20) according to any one of claims 1 to 7, wherein the control unit (26) is configured to determine a voltage setpoint that the power converter (25) must supply to the coil(s) (220, 221), the control unit (26) being electrically connected to the power converter (25).

9. A portable metal detector (20) according to any one of claims 1 to 8, comprising filtering means (250) disposed between the power converter (25) and the coil(s) (220, 221), the filtering means (250) being configured to provide a continuous electric current whose voltage is linear and regulated.

10. A handheld metal detector (20) according to any one of claims 1 to 9, comprising a voltage driver (251) configured to determine the voltage setpoint of the supply current produced by the power converter (25), the voltage driver (251) being connected to the power converter (25).

11. A portable metal detector (20), according to any one of claims 1 to 10, which includes, a remote cord (254) which connects, directly or indirectly, the power converter (25) and the coil(s) (220, 221).

12. A portable metal detector (20) according to any one of claims 1 to 11, wherein the power converter (25) comprises a voltage booster and / or a voltage step-down or a system combining both capabilities.

13. A portable metal detector (20) according to any one of claims 1 to 12, comprising electrical excitation means (28) which are connected directly or indirectly to the power converter (25) and which are configured to transform the electrical current supplied by the power converter (25) into alternating current to excite the terminals of the coil(s) (220, 221).

14. A portable metal detector (20) according to claim 13, wherein the excitation means (28) are disposed in the detection disc (22) in close proximity to the coil(s) (220, 221).

15. A portable metal detector (20) according to any one of claims 13 and 14, wherein the excitation means (28) are disposed at a distance L from the terminals of the coil(s) (220, 221), preferably the distance L is less than or equal to the diameter of the detection disc (22), in particular, the distance L is less than or equal to 30 cm, and preferably the distance L is less than or equal to 10 cm.

16. A portable metal detector (20) according to any one of claims 1 to 15, comprising an amplification and filtering chain (200) for the captured signals and an analog / digital converter (201) configured to transform the captured signals in an analog manner into digital signals, preferably the analog / digital converter (201) and the amplification and filtering chain (200) are arranged in the detection disc (22).

17. A portable metal detector (20) according to any one of claims 1 to 15, comprising: - an analog processing and conditioning means enabling the transport of information to a remote analog / digital conversion module, or - analog detection without conversion to the digital domain.

18. A portable metal detector (20) according to any one of claims 1 to 17, wherein the detection disc (22) comprises coils (220, 221) that cross and overlap at least partially in the disc detection (22).

19. A handheld metal detector according to any one of claims 1 to 18, wherein the transmitters / receivers (260, 271) of the control box (27) and the control unit (26) are wireless.

20. A portable metal detector (20) according to claim 19, wherein the wireless transmitters / receivers (260, 271) operate according to a radio, optical or acoustic communication protocol.

21. A handheld metal detector according to any one of claims 1 to 20, wherein the transmitters / receivers (260, 271) of the control box (27) and the control unit (26) are wired, a cable extending between the control box (27) and the control unit (26) to enable the transmitters / receivers (260, 271) to communicate.

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