METAL DETECTOR HAVING TRANSMITTER WITH ACTIVE MAGNETIC COMPENSATION

Abstract

A metal detector includes at least one sensor that enables to detect the magnetic field created by the transmitter, an error detection system that enables to determine the distortion by comparing the detected magnetic field to the ideal function, and a corrective system which enables to eliminate the distortion by the additional magnetic field that is created according to the detected distortion and/or by the current or voltage applied to the transmitter.

Claims

1- A metal detector, comprising: a transmit coil driven with a rectangular wave pulse signal, a receive coil, at least one sensor configured to detect a magnetic field created by the transmit coil, an error detection system configured to determine a distortion by comparing a detected magnetic field to an ideal function, and a corrective system configured to eliminate the distortion by an additional magnetic field created according to a detected distortion and/or by altering a current by a voltage applied to the transmit coil, wherein the at least one sensor comprises a magnetoresistive sensor.

2- The metal detector according to claim 1, wherein the at least one sensor comprises at least one field measurement coil and/or at least one sensor having a magnetic field sensing feature.

3. The metal detector according to claim 2, wherein the at least one sensor comprises a hall effect sensor and/or a magnetic flux gate sensor and/or a micro electromechanical sensor (MEMS) and/or a Lorentz Force based sensor and/or a piezoresistive sensor and/or a magnetic sensor operating with optical sensing and/or a resonator based a magnetic sensor and/or an eddy current based a magnetic sensor.

4-(canceled)

5-(canceled)

6- The metal detector according to claim 2, further comprising at least one magnetic receiver input circuit configured to convert a magnetic field signal detected as a potential difference (voltage) by the at least one sensor and/or the at least one field measurement coil to subsequent electronic circuits at appropriate levels.

7- The metal detector according to claim 1, further comprising at least one analog digital converter and/or multi channeled analog digital converter enabling a conversion in order to compare received signal to a ideal sample.

8-(Currently Amended) The metal detector according to claim 2, further comprising at least one integrator is positioned between magnetic receiver input circuit and an analog digital converter when the at least one field measurement coil is used.

9- The metal detector according to claim 1, further comprising at least one controlled current source configured to create a corrective signal generated by using active and/or passive elements.

10- The metal detector according to claim 9, further comprising a current source isolation circuit enabling the at least one controlled current source to be isolated electrically from a system voltage and isolating supply and control inputs and/or output of the at least one controlled current source from the system voltage.

11- The metal detector according to claim 9, further comprising at least one field correction coil configured to apply the corrective signal generated in the at least one controlled current source on the magnetic field created by the transmit coil.

12- The metal detector according to claim 1, further comprising at least one controlled constant voltage source constituted by active or passive components, in order to generate a corrective signal.

13- The metal detector according to claim 17, further comprising at least one switching component to apply a voltage generate by a controlled constant voltage source (17) onto the transmit coil.

14- The metal detector according to claim 17, wherein a current of the transmit coil (3) is maintained using a constant voltage switched to the transmit coil and a level of the current is controlled using a ramping time interval.

15- The metal detector according to claim 1, further comprising a field correction coil positioned as an independent coil and/or included within at least one winding of the transmit coil.

16- A method for enabling sensing of a distortion in a magnetic field created by a transmit coil in a metal detector and a correction of a sensed distortion in the magnetic field, consisting of the following process steps; converting an instant value or a time derivative of the magnetic field generated by the transmit coil to an electrical signal; determination of an error signal by comparing the magnetic field generated to an ideal function; generating a corrective signal by using the error signal; adding the corrective signal to the magnetic field created by the transmit coil directly or indirectly using at least one electronic and/or electronic/magnetic system.

17- The metal detector according to claim 1, further comprising a field correction coil consisting of at least one turn of the transmit coil, wherein an output of a controlled current source is configured to be connected to an internal wire through winding of the transmit coil.

18- The metal detector according to claim 6, further comprising at least one integrator positioned between the at least one magnetic receiver input circuit and an analog digital converter when the at least one field measurement coil is used.

19- The metal detector according to claim 7, further comprising at least one integrator positioned between a magnetic receiver input circuit and the at least one analog digital converter when the at least one field measurement coil is used.

20- The metal detector according to claim 10, further comprising at least one field correction coil configured to apply the corrective signal generated in the at least one controlled current source on the magnetic field created by the transmit coil.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1: A block diagram of the time domain metal detector comprising magnetic field measurement and compensation by means of a magnetic sensor.

[0025] FIG. 2: A block diagram of the time domain metal detector comprising magnetic field and compensation by means of the field measurement coil.

[0026] FIG. 3A: In a detector operating in the time domain the graphical illustration of the transmit coil voltage.

[0027] FIG. 3B: In a detector operating in the time domain the graphical illustration of the magnetic field which is accepted as ideal.

[0028] FIG. 3C: In a detector operating in the time domain the graphical illustration of the magnetic field which comprises parasitic effects.

[0029] FIG. 3D: In a detector operating in the time domain the graphical illustration of the magnetic field which is required to be created for eliminating the parasitic effects.

[0030] FIG. 3E: In a detector operating in the time domain the graphical illustration of the change of the parasitic magnetic field and corrective magnetic field according to time.

[0031] FIG. 4A: A first block diagram of the magnetic field injection over the transmit coil windings.

[0032] FIG. 4B: A second block diagram of the magnetic field injection over the transmit coil windings.

[0033] FIG. 5: System Control Diagram

DESCRIPTION OF THE REFERENCE NUMBERS

[0034] 20—Digital Processing Unit [0035] 21—Transmitter Driver Circuit [0036] 22—Transmit coil [0037] 23—Field measurement coil [0038] 24—Magnetic sensor [0039] 25—Magnetic receiver input circuit [0040] 26—Integrator [0041] 27—Analog digital converter (ADC) [0042] 28—Digital analog converter (DAC) [0043] 29—Current source isolation circuit [0044] 30—Controlled current source [0045] 31—Field correction coil [0046] 32—Receive coil [0047] 33—Receiver input circuits [0048] 34—Signal preprocessing circuits [0049] 35—Analog digital converter (ADC) [0050] 36—Controlled constant voltage source [0051] 37—Switching component [0052] 38—Switching component [0053] 101-105: The voltage applied to transmit coil [0054] 111-115: Ideal magnetic field required to be created by transmit coil [0055] 121-126: The magnetic field created by transmit coil [0056] 131-138: Corrective magnetic field [0057] 207—System reference [0058] 208—Uncompensated transmitter system [0059] 209—Ideal transmitter function [0060] 210—Sampling system [0061] 211—Corrective Coil System [0062] 212—Magnetic sensor system

Detailed Description of the Embodiments

[0063] In FIG. 3A, a voltage required to be applied on the coil ends for obtaining the required current through an ideal coil is seen. In case this voltage is applied to an ideal coil, the current flows through this coil and the magnetic field is generated as shown in the graph depicting both waveforms since both are proportional. However the parasitic effects cause the current in a real coil differ from the current of an ideal coil, additionally, cause the generated magnetic field to be differ from the current in a nonlinear manner. Among these parasitic effects, the ones influenced from the capacitive reasons have dynamic characteristic and the disturbances are realized following the transitions in the signal. The effects due to resistive reasons are present whether there is a transition in the signal or not. The presence of both of them exhibits a network behavior, two parasitic effects influence each other, however if change and stability are separated sufficiently, then it may be possible to illustrate and distinguish both effects in the same graph. In this manner one graph in FIG. 3C; is closer to real case which includes parasitic effects of the magnetic field that is created by a real coil. In FIG. 3A when a rectangular wave voltage form referenced as (101) (102) (103) and (104) levels are applied on the ends of an ideal coil, they respectively form the ideal current in FIG. 3B (111), (112), (113) (114), thus the ideal magnetic field, the wave form in FIG. 3B is an integral of the wave form in FIG. 3A with respect to time. In FIG. 3A, wave form indicated as close to the rectangular wave form is in pulse form in real applications (101), (103) with narrow intervals, (102) and (104) wide intervals however due to ease of expression, these four times intervals are shown closer to each other within the scope of FIG. 3A-FIG. 3E.

[0064] In FIG. 3C, the parasitic effect which is expressed as non-ideal, close to real signal form (121) shows the disturbed condition of the transition from (111) to (112) as a result of its change over the voltage (102) level in FIG. 3A. The main characteristic of this disturbance which is similar to a damped oscillation is determined by means of the capacitive interaction between the inductive coil windings. This disturbance affects each coil winding current separately and also the magnetic field as a result. The same parasitic effects are the results of the transition respectively from (102) and (103) to (123) and from (103) to (104) as (124) and from (104) to (105) as (126).

[0065] In FIG. 3C, the resistive effect is also shown. This effect is the result of voltage level (102) (shown as 0V which also means ends are short-circuit) over a non-ideal coil causing current decrease due to the internal resistance of the non-ideal coil. Although it seems like linear downramp, in case the internal resistance of the coil is stated as a serial resistance, this decrease is mentioned as 0V application over the internal resistance of a coil (R.sub.Tx) with inductance (L.sub.Tx) is expressed by;

i(t)=i.sub.0e.sup.t/(L.sup.Tx.sup./R.sup.Tx)

[0066] This exponential expression within a predetermined time interval is closer to a linear downslope decrease and the decrease which can be seen in (122), can be seen partially independent from the parasitic effect based on the dynamic change in (121).

[0067] The waveform which can be able to gain the form in FIG. 3B when it is arithmetically summed with the wave form in FIG. 3A-FIG. 3E is shown in FIG. 3D. It is important that, the form which is referred as (131) in this wave form shall be with totally inverse of the form which is referred as (121). The detail in respect to this section is shown closely in FIG. 3E. Although there is a mutual coupling between the components which will constitute both fields, when this process is realized within a feedback loop, it is possible to express the process as a sum.

[0068] In the preferred embodiment, in a metal detector operating in the time domain, as shown in FIG. 1 and FIG. 2; the signal is received by Receive Coil (13) and processed by the receiver input circuits (14) and signal preprocessing circuits (15) then digitized by means of the analog digital converter (16). These processes are realized in (112) and (114) periods in FIG. 3B. Making measurements in (101) and (103) intervals are also meaningful for a metal detector where the measurement of magnetic characteristics of the target and the environment is required. However in a metal detector wherein the present state of the art is practiced, the effects of the transitions of the magnetic field following (133), (134), (137) and (138) regions and the subsequent regions of the signal in FIG. 3D can be neglected.

[0069] The main technique of the invention consists of a compensation using a sub-system by superposition principle which will create minimum distortion in total by means of measuring the distortion seen in FIG. 3C and applying corrective signal by magnetic and/or electronic means seen in FIG. 3D. For this reason the below described system is realized and the system following this description is created by the compensation process within the context of its flow. The preferred embodiment of the invention is the system which is shown in FIG. 1 as a block diagram. The system which is shown in FIG. 2 as a block diagram operates in the same manner however the diagrams are different in respect to realize the measurement by means of using coil or magnetic sensor. When a magnetic field measurement is performed with a coil, according to the Faraday's Law of Induction, the signal generated is time derivative of the magnetic flux according to time, for including the received signal therefrom to the mathematical fact, it is required to take its integral according to time or calculating this signal by considering that it is a derivative. The difference between two measurement methods which will have an effect upon the result is obtaining higher amplitude in fast signal changes of the measurement made by means of the coil, on the other hand lower signal-noise ratio (SNR) in slow changes and thus a decrease in signal measurement accuracy and precision. On the contrary, the fast magnetic sensors which can operate within the magnetic fields created by the detectors are qualified sensors and their costs are higher when compared to the coil costs.

[0070] The Digital Signal Processing Unit (1) circuit within FIG. 1 consists of a processor which generates The in the digital signals, maintains analog processes by means of ADC/DAC or equivalent circuit elements, and has a digital signal processing capability. This process is realized by means of electronic elements which are formed by the embedded controllers, digital signal processors (DSP), field programmable gate arrays (FPGA) or by variation and combinations thereof, is integrated, has digital processing ability. For this reason, in conjunction with the other sections of the design, an appropriate Digital Processing Unit (1) can be selected with a processing ability based on the optimization according to cost and purpose. In the preferred embodiment, an FGPA is used which embodies an integrated Processor. This Digital Processing Unit (1) also generates the digital signals which will constitute the reference for the magnetic field of the transmitter of the metal detector. These signals provide high current in the coil by the Transmitter Driver Circuit (2) that consists of various digital switching elements and to recover energy from the magnetic circuit of the Transmit coil (3). In the state of the art, there are many half or full H-Bridge transistor and driver configuration designs not only for the Transmit coil (3) but also for motor drive and similar aims and in the direction of said aim, one of them can be used. The coil driven by this power electronic circuit is a typical with double D (receiver/transmitter) or double receiver D (receiver/transmitter/receiver) or a transmitter winding of the metal detector coil based on induction balance. In the preferred embodiment a receiver/transmit coil with double D structure is used.

[0071] In order to measure the magnetic field that is created with this coil, a magnetic sensor (5) is located to the location where the coil generates an optimum field, in preferred embodiment it is located to the planar surface center of the transmit coil (3). In the structure of FIG. 2 which is an alternative form of this system, the field measurement coil (4) which will take the magnetic field generated by the transmit coil (3) as optimum, can be located near to the windings of the transmit coil (3). Here an important aspect is that; regardless of whether using the magnetic sensor (5) or the field measurement coil (4), receiving the field created by the transmit coil (3) in an optimum magnitude to conform the connected electronics. The reason for this, it is provided that the Magnetic sensor (5) or the Field measurement coil (4) is not influenced by the environmental signals which are not generated “directly” by means of the Transmit Coil (3), in other words by the target signals or the signals generated by means of the environmental factors with high permeability and conductivity as little as possible and they are allowed for receiving the linear signal basically by the field generated by the transmitter.

[0072] On the other hand, the magnetic field that is created by fast signal changes in the field measurement coil (4) may be more than desired or the magnetic field to which the magnetic sensor (5) is subject, may be above the limits, thus this condition is a variable based on the design. In this case, the location of the field measurement coil (4) or the magnetic sensor (5) can be altered in a manner such that they can be able to sense magnetic field at a lower magnitude. Here, an important aspect is that; it can be disadvantageous to move the field measurement coil (4) or the magnetic sensor (5) away from the planar plane and symmetry of the transmit coil (3). The signal which is converted into potential difference (voltage) by means of the Magnetic Sensor (5) or the Field Measurement Coil (4) is converted to the levels by means of a Magnetic Receiver Input Circuit (6) to which the following stages of electronic circuit can operate. Since the signals received by this circuit are relatively fast (at nanosecond-microsecond level), the characteristics of this circuit are all important. This circuit mainly consists of a band pass filter with amplifier. The output of the Magnetic Receiver Input Circuit (6), is connected directly to the Analog Digital Converter (8) circuit in an embodiment where the Magnetic Sensor (5) is preferred, in case the Field Measurement Coil (4) is used, it will be more appropriate to connect to the Analog Digital Converter (8) through an Analog Integrator (7). Although the mathematical integration process can be realized during digital signal processing period however when we consider the cases where the derivative gives low result for the analog digital converter (8), in order to keep the required accuracy and precision for digitizing, it will be more beneficial to realize this process using analog means. Despite the sampling speed of the Analog Digital Converter (8) is required to be at MS/s range (million samples per second) for an effective result, its resolution can be selected relatively low. Although it is not used in the preferred embodiment, in order to improve the total digital resolution, a plurality of Analog Digital Converter (8) or a multichannel Analog Digital Converter (8) can be used, in mathematical processes the derivative of the signal can be processed together with the signal itself.

[0073] The difference between the signal received from the analog digital converter (8) and the referenced signal is the error signal. The error signal is an amplitude that belongs to the magnetic field and the correction signal is required to have the form of the magnetic field. In accordance with the Biot-Savart law, it is known that the magnetic field created due to an electric current is directly proportional with the current. When scaled negative (multiple of −k) is applied, it is possible to obtain the required correction by superposition. In generating the corrective magnetic field, the number of windings is preferred to be less, preferably single, because if the number of windings increase, it will create parasitic effects in the corrective magnetic field as it is in the transmit coil (3). Lower number of windings means to put away the benefit of multiplying the magnetic field based on the number of tours (B α NI). The duration and amplitude of the corrective magnetic field on the ring effect is relatively small within the total duration. For this reason, the current intensity does not constitute a problem. Since the circuit is electrically isolated from the voltage of rest of the system which creates the corrective current and the controlled current source (11), it decreases the capacitive effects and enables flexibility in realizing the current source electronically. For this reason at the source and control inputs of a controlled current source (11), there is a Current Source Isolation Circuit (10). The circuit which controls the current source is a Digital Analog Converter (9) which converts the calculated digital correction information provided by means of the Digital Processing Unit (1) to an analog voltage level. These three sections are required to operate as fast as at least the Analog Digital Converter (8). The Controlled Current Source (11) drives the Field Correction Coil (12). Here the fact that the Field Correction Coil (12) shall not physically apart from the Transmit Coil (3), constituted the same physical shape completely and overlap; otherwise, the magnetic fields generated by two coils may not exhibit regularity in the space around the coil. Arrangement of these two coils totally one in the other is also a situation which is not desired. Although the Current Source Isolation Circuit (10) substantially eliminates the capacitive effects between two systems (one of the aims is this) leaving an optimal distance is beneficial in terms of the stability of two circuits. In this embodiment, it is not possible to use a voltage source for driving the Field Correction Coil (12), in this section it is necessary to use the Controlled Current Source (11). Since these coils share the same magnetic field between the Transmit Coil (3) and the Field Correction Coil (12), there is a mutual induction and the magnetic field created by means of the Transmit Coil (3) causes a magnetic induction on the Field Correction Coil (12), in other words causes a voltage. In order to realize an accurate superposition in the magnetic field, the current of the Field Correction Coil (12) shall be a current which can be controlled independently from this induction.

[0074] Rather than the Field correction coil (12) is an independent coil, it is possible to use the windings of the transmit coil. In this configuration seen in FIG. 4A, the Field Correction Coil (12) consists of windings which can be at least one turn or at most all turns of the Transmit coil (3). In this case, since one end of each coil system will be common, a full isolation is not possible however this section of the invention can be formed in this manner for particularly resistive parasitic effects and both separate coil and a section of the transmitter can be used. The resistive parasitic effect is an effect which is lasting with longer periods during the period, requires to create more magnetic fields in average although it is a slow effect, for this reason in order to generate averagely more magnetic induction with a lower current, for increasing the N.I multiplication which forms the magnetic field, N (tour numbers) can be increased. In this case, the output of the Controlled Current Source (11) within the scope of the invention is required to be realized in a manner such that it is connected to an internal wire through winding of the Transmit Coil (3) seen in FIG. 4A. This section can be realized by means of a circuit which is isolated by a Current Source Isolation Circuit (10) which is mentioned above, consists of less number of tours in order not to create capacitive interaction. Although constant current source solution is a self-regulating and adaptive option, the current sources are high-impedance sources and it is limiting due to the parasitic characteristics of the switching elements during switching process of the inductive load which consists of a multi-turn coil. As an alternative solution, as can be seen in FIG. 4B, the coil current can provided to be constant by means of switching the generated voltage by a controlled constant voltage source (17) on the transmit coil (3) via the voltage switching components (18) (19). This configuration can be established using simpler components than those in FIG. 4A, but it can be beneficial for controlling the current distortion due to the internal resistance of the Transmit Coil (3). The voltage of the Controlled voltage supply (17) is determined by means of the Digital Analog Converter (9) and the time intervals of this voltage for keeping it constant is applied on the durations in FIG. 3B (112) and (114). This level of voltage is controlled by said magnetic field measurement in order to obtain a constant magnetic field.

[0075] The calculation that is realized in the Digital Processing Unit (1) and active compensation process consist of basically the ideal magnetic field formulation, measurement of the generated magnetic field and generating the corrective signal for eliminating the difference between them. The physical system in FIG. 1 is expressed as a process in FIG. 5. The System Reference (201), Ideal Transmitter Function (203), Sampling System (204), calculation process section of the Correction System (205) in FIG. 5 are the processes executed by the Digital Processing Unit (1) in FIG. 1 and FIG. 2. The Uncompensated Transmitter System (202) in FIG. 5 constitutes the process which comprises the Transmit Coil Driver Circuit (2) in FIG. 1 and FIG. 2 and the Transmit Coil (3) which is particularly one of the most important reasons for disturbance, aims correcting its output. The system which is expressed as a Sensor System (206) in FIG. 5 consists of Magnetic Receiver Input Circuit (6), Analog Digital Converter (8) in addition to the Magnetic Sensor (5) in FIG. 1 or the Field Measurement Coil (4) system in FIG. 2. In this system if sensing is made by means of the Field Measurement Coil (4), also the Integrator (7) in FIG. 2 can be used. The Digital Analog Converter (9), the Current Source Isolation Circuit (10), the Controlled Current Source (11) and the Field Correction Coil (12) in FIG. 1 and FIG. 2 constitute the process at the output of the Correction System (205) in FIG. 5.

[0076] As it can be seen in the system control diagram of FIG. 5, the voltage pulses form the System Reference (201). This reference is same with the voltage signal form seen in FIG. 3A. The integral of this signal form within time domain seen in FIG. 3B, is the magnetic field required to be generated by the Transmit Coil (3) when the parasitic effects are excluded. The Ideal Transmitter Function (203) seen in FIG. 5 provides analytic equivalent of this field and in the Laplace domain with system parameters, this function can be expressed as follows; M(s)=k/s [1] Here the k value is a scaling value, and is a value which can be calculated according to the measurement results by the Digital Processing Unit (1) in the FIG. 1 and FIG. 2. “1/s” in [1] statement is the equivalent of the Laplace transform of the integral process in time domain. In the time field, the integral of the rectangular wave form of (101), (102), (103) and (104) in FIG. 3A-FIG. 3E is the wave form of (111), (112), (113) and (114) in the same figure. This wave form is an “ideal model”, its uncorrected situation is formed by means of the Transmitter Driver Circuit (2) and the Transmit Coil (3) in FIG. 1 and FIG. 2, at the same time the form of the magnetic field to be created by means of the Uncorrected Transmitter System (202) in FIG. 5 will be similar to the wave form in FIG. 3A-FIG. 3E. The difference between the Magnetic Sensor System (206) output which measures the transmitter magnetic field in FIG. 5 and the Ideal Transmitter Function (203) will give the signal between the desired and the generated, namely the “error signal”. The sampling system (204) is a system where the record of the error signal occurred along at least one signal period within the time domain and the compensation is realized after it is added to the output of the uncompensated transmitter system (202) by means of the Correction System (205). The easiest method for correction is to add the records to the present time domain records in the sampling system (204) after summing; however in order to improve the system stability in the long term, a digital filter can be devised to the sampling system (204). In the preferred embodiment, the sampling system (204) logs to record in the time domain and after digital filtering, it updates these records. However this illustration system (204) is not required to operate in the time domain, instead of this, this function can be defined in an analytically by means of analytical function modeling methods. In any case, this correction function is required to operate in a synchronous manner with the ideal transmitter function (203) and at the same time it is cyclic. In such a system, if the uncompensated transmitter system (202) is designed as time invariant, establishing the sampling system (204) with the System Identification (SI) only when the device is initially operated or with determined reasonable intervals or whenever the user requires. The magnetic field which is required to be added for correction is as it is in FIG. 3D.

[0077] As an alternative, it is possible to obtain the same functionality of the Controlled Constant Voltage Source (17) by using a constant voltage source fixed to an optimum voltage and setting a current to a level that will be constant in intervals (112) and (114) only by varying the time interval of (111) and (113) in FIG. 3B. In this method, the constant current is obtained by using the coil current as the parameter in the relation between the coil current, a constant voltage and the parasitic resistance. This parameter can be controlled by the Digital Processing Unit (1) by setting the pulse width since the targeted current is a function of the ramp interval and the inductance (the slope of ramp).

[0078] The compensation process is realized as a digital active system in the preferred embodiment however as different circuits which will create and analog or digital context, also it is possible to establish a compensation system which will make adjustment in the signal by means of the digitally supported or unique analog principles. In any of the cases, the following main processes will be applied directly or indirectly as a closed loop or in a predetermined order.

[0079] D) Converting the instant value or the time derivative of the magnetic field to an electrical signal

[0080] E) Determination of the error by comparing the generated magnetic field to the ideal function

[0081] F) Adding the corrective signal to the magnetic field directly or indirectly by means of at least one electronic and/or electronic/magnetic system.

[0082] In the preferred embodiment, the corrective signal is added to the magnetic field using a separate coil however it is possible to realize the signal, particularly the signal within the resistive region by means of analog and digital processes by injecting current to the transmit coil and by making addition on the coil voltage by this method. Since the correction of the capacitive effects by means of a method except creating a magnetic field is not an easy process, the correction process can be realized alternatively as a system which can be able to eliminate the resistive effects by current or voltage superposition on at least one winding of the transmit coil (3), the capacitive effects by means of injecting to the partial windings of the transmit coil (3). Here it is possible to correct the capacitive effects with a system which is fast however does not require considerable energy in total. Regardless of how the transmitter injection is made for this correction, in order to eliminate the system from the internal capacitive parasitic effects, it is required to be realized with the possible lowest number of windings. In correcting the resistive effects, magnetic field and/or current injection will be take part for relatively a long interval correction. For this reason in order to realize this correction with single or less number of tours, a high average current will be required, thus for obtaining the required magnetic flux, the number of tours shall be higher to have the required (N.I) (current.tour) value. Thus, in this case the relevant coil of the transmitter or an independent coil are required to have a plurality of tours. In order to eliminate both parasitic effects, it is possible to use both methods in conjunction.