CN102176063A - Primary field self-counteracting device for time-domain airborne electromagnetic method - Google Patents

Abstract

The invention relates to a primary field self-cancellation device of the time-domain airborne electromagnetic method. The aircraft is equipped with a data recording system, and the cross-shaped bracket supporting the transmitting coil, z-component receiving coil, x-component receiving coil, y-component receiving coil and calibration coil is hung on the bottom of the aircraft cabin by hanging ropes, the z-component receiving coil, x-component receiving coil, x-component receiving coil The component receiving coil and the y component receiving coil are connected to the preamplifier through wires, and then connected to the data recording system through signal wires. Compared with the existing similar products, the influence of the primary field on the receiving coil is effectively reduced, and the dynamic range of the secondary field signal received by the receiving coil is greatly increased, which improves the accuracy and efficiency of exploration. The receiving coil adopts a double shock-absorbing structure, which effectively protects the receiving coil and avoids The impact of device vibration on the received signal improves the receiving quality of the signal in the late stage of the secondary field. The calibration coil and the three receiving coils form a 45-degree angle at the same time, which is convenient for the staff to check the system performance at any time and improves the system detection efficiency.

Description

Primary field self-cancellation device for airborne electromagnetic method in time domain

Technical field:

The invention relates to an aerial geophysical survey receiving device, in particular to a pod-type helicopter time-domain aerial electromagnetic survey device.

Background technique:

The pod-type helicopter aerial time-domain electromagnetic exploration system uses a helicopter as a flight carrier to excite the underground medium by transmitting a high-power magnetic field signal. During the transmission gap of the magnetic field signal, the receiving device is used to receive the secondary energy produced by the underground medium due to the eddy current effect. field to explain the subsurface resistivity structure. The pod-type helicopter aeronautical time-domain electromagnetic survey receiving device is a part of the aeronautical time-domain electromagnetic survey system, including induction coils or magnetic induction sensors, signal conditioning modules, data acquisition and processing systems, and calibration coils for checking whether they are working normally. The core of the receiving device is the induction coil or the magnetic induction sensor, and its installation method directly determines the receiving quality of the signal. At present, the installation methods of the receiving device mainly include the helicopter pod type integrated with the transmitting device and the fixed-wing independent hanging type. The receiving components include single-component (z component), double-component (x, z-component) and three-component (x , y, z) three types, the positions of the two-component and three-component receiving devices are different.

The existing well-known research and development units of the pod-type helicopter aviation electromagnetic system in the world mainly include Geotech Company, Fugro Company and Aeroquest Company. Some methods, such as the "buckingcoil" feedback coil design adopted by Geotech Company and Aeroquest Company, and the position adopted by Fugro Company to place the receiving coil between the transmitting coil and the helicopter, etc.

At present, except some articles on podded time-domain electromagnetic theory have been published in China, there is no mature podded helicopter airborne electromagnetic system.

Using the "buckingcoil" feedback coil design to reduce the influence of the primary field will not only increase the total weight of the device due to the use of the "buckingcoil" coil, but also reduce the total magnetic moment of the transmitting coil, reducing the exploration depth of the device and affecting the exploration effect . The method of placing the receiving coil between the transmitting coil and the helicopter will not increase the weight of the device itself, but the distance between the receiving coil and the target will increase, reducing the signal strength of the secondary field, which will also affect the exploration effect. At present, there is no report of a device that uses the primary field self-cancellation method for three-component measurement at home and abroad, and there is no report that uses a calibration coil to simultaneously calibrate three component receiving coils.

Invention content:

The object of the present invention is to provide a primary field self-cancellation device suitable for the time-domain airborne electromagnetic method to solve the problem that the dynamic range of the secondary field signal is too small due to the large amplitude of the primary field.

The purpose of the present invention is achieved in the following manner:

Helicopter 13 is equipped with data collection system 7, and DC power is provided by helicopter 13, and cross-shaped bracket 9 supports transmitting coil 10, x component receiving coil 2, y component receiving coil 3 and calibration coil 14, and calibration coil 14 passes wire Connect with the data collection system 7, the upper end of the hanging rope 12 is tied to the bilge of the helicopter 13, the lower end of the hanging rope 12 is tied to the center of the cross-shaped bracket 9, the upper end of the hanging spoke 11 is tied to the middle part of the hanging rope 12, The lower ends of the hanging spokes 11 are tied on the transmitting coil 10 at equal angles, and the hanging spokes 11 are of unequal length from front to back, and their length depends on the flight speed of the helicopter 13. The z-component receiving coil 1 is mounted on the transmitting coil 10 through the shock pad 8 Above, the effective area of the z-component receiving coil 1 is divided into two parts by the transmitting coil 10, the excitation magnetic field generated by the transmitting coil 10 is divided into two parts in the z-component receiving coil 1, and the total magnetic flux is equal in magnitude and opposite in direction, and the x-component receiving coil 2 Located at the center of the transmitting coil 10, both perpendicular to the z component receiving coil 1 and perpendicular to the flight direction of the helicopter 13, the y component receiving coil 3 is perpendicular to both the z component receiving coil 1 and the x component receiving coil 2, and Orthogonal to the x-component receiving coil 2, the z-component receiving coil 1, the x-component receiving coil 2 and the y-component receiving coil 3 are connected to the preamplifier 5 through the wire 4, and then connected to the data recording system 7 through the signal line 6, The calibration coil 14 is located in the middle of the z-component receiving coil 1, the x-component receiving coil 2 and the y-component receiving coil 3. When the receiving coil is working normally, the calibration coil 14 is in an open circuit state. When the calibration coil 14 is closed, it is used as a standard abnormality verification reception Whether the coil is working properly.

The outside of the transmitting coil 10 and the cross-shaped support 9 is wrapped with glass steel pipes, and the shape of the transmitting coil 10 is a circle or any regular polygon. The z-component receiving coil 1, the x-component receiving coil 2 and the y-component receiving coil 3 are all hollow structures, which are circular or regular polygonal. The z-component receiving coil 1, the x-component receiving coil 2 and the y-component receiving coil 3 are all wound with copper tape and grounded for interference shielding.

Z-component receiving coil 1, x-component receiving coil 2 and y-component receiving coil 3 all adopt double-layer damping structure, z-component receiving coil 1, x-component receiving coil 2 and y-component receiving coil 3 are all made of shielded coil 15 larger than Elastic rubber strips 16 connecting three groups of cross-orthogonal coils to the inner casing are elastically connected to the coil inner casing 17, and the coil inner casing 17 is connected to the coil outer casing by elastic rubber strips 20 connected to the outer casing and the cross-orthogonal inner casing of more than three groups 19 are elastically connected, and the joints are respectively fixed with elastic rubber strip holders 18 to form.

The calibration coil 14 forms an included angle of 45 degrees with the z-component receiving coil 1 , the x-component receiving coil 2 and the y-component receiving coil 3 .

Beneficial effects: The pod-type helicopter aviation time-domain electromagnetic method primary field self-cancellation device can effectively reduce the influence of the primary field on the receiving coil by using the spatial distribution of the magnetic flux generated by the transmitting coil without increasing the overall weight. The dynamic range of the secondary field signal received by the receiving coil is greatly increased, so that the system exploration effect is more ideal, and its superiority is obvious compared with other similar foreign systems. The receiving coil adopts a double shock-absorbing structure based on elastic rubber. In addition to effectively protecting the receiving coil, it can also avoid the impact of device vibration on the received signal during flight and improve the receiving quality of the late signal of the secondary field. In addition, the use of the calibration coil which forms an angle of 45 degrees with the three receiving coils at the same time facilitates the staff to check the working performance of the system at any time during the flight of the device and improves the detection efficiency of the system.

Description of drawings:

Figure 1 is a structural diagram of the primary field self-cancellation device for the time-domain airborne electromagnetic method

Fig. 2 is a sectional view of receiving coils 1, 2, 3 in Fig. 1

1z component receiving coil, 2x component receiving coil, 3y component receiving coil, 4 wires, 5 preamplifiers, 6 signal lines, 7 data recording system, 8 shock pads, 9 cross-shaped brackets, 10 transmitting coils, 11 device hanging Spokes, 12 hanging ropes, 13 helicopters, 14 calibration coils, 15 shielded coils, 16 elastic rubber strips connecting the coils to the inner shell, 17 coil inner shells, 18 elastic rubber strip fixing seats, 19 coil shells, 20 Elastic rubber strip connecting the inner shell to the outer shell.

Detailed ways:

Below in conjunction with accompanying drawing and embodiment describe in further detail:

Helicopter 13 is equipped with data collection system 7, and DC power is provided by helicopter 13, and cross-shaped bracket 9 supports transmitting coil 10, x component receiving coil 2, y component receiving coil 3 and calibration coil 14, and calibration coil 14 passes wire Connect with the data collection system 7, the upper end of the hanging rope 12 is tied to the bilge of the helicopter 13, the lower end of the hanging rope 12 is tied to the center of the cross support 9, the upper end of the hanging spoke 11 is tied to the middle part of the hanging rope 12, four More than two hanging spokes 11 lower ends are tied on the transmitting coil 10 at equal angles, and the hanging spokes 11 are unequal lengths before and after, and its length depends on the flight speed of the helicopter 13. On the transmitting coil 10, the effective area of the z-component receiving coil 1 is divided into two parts by the transmitting coil 10, and the excitation magnetic field generated by the transmitting coil 10 is divided into two parts in the z-component receiving coil 1, and the total magnetic flux is equal in magnitude and opposite in direction, and the x component The receiving coil 2 is located at the center of the transmitting coil 10, which is perpendicular to the z-component receiving coil 1 and the flying direction of the helicopter 13, and the y-component receiving coil 3 is perpendicular to both the z-component receiving coil 1 and the x-component receiving coil 2, and is orthogonal to the x-component receiving coil 2, the z-component receiving coil 1, the x-component receiving coil 2 and the y-component receiving coil 3 are connected to the preamplifier 5 through the wire 4, and then connected to the data recording system through the signal line 6 7, the calibration coil 14 is located in the middle of the z-component receiving coil 1, the x-component receiving coil 2, and the y-component receiving coil 3. When the receiving coil is working normally, the calibration coil 14 is in an open state, and when the calibration coil 14 is closed, it is used as a standard Exception Verify that the receiving coil is working properly. The outside of the transmitting coil 10 and the cross-shaped support 9 is wrapped with glass steel pipes, and the shape of the transmitting coil 10 is a circle or any regular polygon. The z-component receiving coil 1, the x-component receiving coil 2 and the y-component receiving coil 3 are all hollow structures, which are circular or regular polygonal. The z-component receiving coil 1, the x-component receiving coil 2 and the y-component receiving coil 3 are all wound with copper tape and grounded for interference shielding. Z-component receiving coil 1, x-component receiving coil 2 and y-component receiving coil 3 all adopt double-layer damping structure, z-component receiving coil 1, x-component receiving coil 2 and y-component receiving coil 3 are all made of shielded coil 15 through More than three groups of cross-orthogonal coils are elastically connected to the elastic rubber strip 16 connected to the inner shell and the coil inner shell 17, and the coil inner shell 17 is composed of more than three sets of cross-orthogonal inner shells and the elastic rubber strip 20 connected to the outer shell and the coil The shell 19 is elastically connected, and the joints are fixed by elastic rubber strip fixing seats 18 respectively. The calibration coil 14 forms an included angle of 45 degrees with the z-component receiving coil 1 , the x-component receiving coil 2 and the y-component receiving coil 3 .

Example 1

The outside of the transmitting coil 10 is encapsulated by glass steel tubes, and after encapsulation, it is fastened by a cross-shaped bracket 9, and the spokes 11 and the suspension ropes 12 are suspended on the lower part of the helicopter 13 through the device. The z-component receiving coil 1 is placed on the upper part of the transmitting coil 10 after being damped by the shock-absorbing pad 8 and is divided into two parts by the transmitting coil 10. The magnetic flux generated by the transmitting coil 10 is equal in size in the two spaces of the z-component receiving coil 1 in the opposite direction. The x-component receiving coil 2 is perpendicular to the z-component receiving coil 1 and the flying direction of the helicopter 13 , and the center of the x-component receiving coil 2 is on the diameter of the transmitting coil 10 . The y-component receiving coil 3 is perpendicular to the z-component receiving coil 1 and perpendicular to the x-component receiving coil 2 , and the circle center of the y-component receiving coil 3 is on the diameter of the transmitting coil 10 . The output ends of the three component receiving coils 1, 2, and 3 are connected to the preamplifier 5 after the wire 4 of the receiving coil to the preamplifier is extended for a distance of more than 2 meters, and the signal is amplified by the preamplifier 5 and then sent to the preamplifier via the preamplifier. The signal line 6 of the data recording system is sent to the data recording system 7, and the data recording system 7 performs data collection and storage. The calibration coil 14 is located in the middle of the z-component receiving coil 1, the x-component receiving coil 2 and the y-component receiving coil 3. It is in an open circuit state when the receiving coil is working normally. When the calibration coil 14 is closed, it is used as a standard abnormality to verify whether the receiving coil is working. normal.

The shape of the transmitting coil 10 and the three component receiving coils 1, 2, 3 is circular. The three component receiving coils 1, 2, and 3 all adopt a double-layer damping structure. The coils wound by enameled wires are wound with copper tape and grounded for interference shielding. The shielded coils 15 are composed of more than three groups of cross-shaped orthogonal coils. The elastic rubber strip 16 connected to the inner shell is elastically connected to the coil inner shell 17, and the coil inner shell 17 is elastically connected to the coil shell 19 by more than three sets of elastic rubber strips 20 connected to the inner shell and the outer shell in a cross-orthogonal shape. Adopt elastic rubber strip fixing seat 18 to fix. The coil inner shell 17 is made of hard PVC plastic, and the coil shell 19 is made of glass steel pipe. The calibration coil 14 can be circular or polygonal, and can be bent from a steel pipe or wound with multiple turns of enameled wire. The calibration coil forms an angle of 45 degrees with the receiving coils 1, 2, and 3 at the same time. The opening and closing of the calibration coil 14 is at the discretion of the system operator on board the helicopter 13 .

The general expression of the magnetic field induction output signal of the receiving coil 1, 2, 3 can be expressed by the following formula:

$\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; NS</span>}\frac{\mathrm{<span\; class="notranslate">\; dB</span>}}{\mathrm{<span\; class="notranslate">\; dt</span>}}$

For the general structure of the pod-type helicopter aeronautical time-domain electromagnetic method device, the magnetic field acting on the receiving coils 1, 2, and 3 includes two parts: the magnetic field generated by the transmitting coil itself (primary field, represented by B ₁ ) and the underground The magnetic field (secondary field, represented by _B2 ) produced by the medium due to the eddy current effect, so for the receiving coils 1, 2, 3, the expression of the output signal is as follows when there is a transmitting current in the transmitting coil 10:

${\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; NS</span>}\frac{{\mathrm{<span\; class="notranslate">\; dB</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; dt</span>}}$

And when there is no transmitting current in the transmitting coil 10, its expression is then:

${\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; NS</span>}\frac{{\mathrm{<span\; class="notranslate">\; dB</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; dt</span>}}$

Since the current in the transmitting coil exceeds 200 amperes, B ₁ >> B ₂ , resulting in ε ₁ >> ε ₂ , if the primary field is not processed, in order to prevent the receiving coil 1, 2, 3 from causing the output voltage to be too large Saturation affects its normal operation, then the output signals of receiving coils 1, 2, and 3 can only be amplified by low multiples or not amplified or even attenuated, resulting in an unsatisfactory output amplitude of the secondary field signal with a small amplitude. In actual exploration work, the primary field signals of the receiving coils 1, 2, and 3 are useless, and suppressing or canceling their amplitudes is beneficial to the amplification of the secondary field signals in order to obtain an ideal secondary field signal.

When the transmitting coil 10 generates a primary field, the inner and outer sides of any arc will generate magnetic fields of equal magnitude and opposite directions, respectively denoted as B _{1 inside} and B _{1 outside} , and the z-component receiving coil 1 placed on it is divided into The two areas are respectively represented as S _{1 inside} and S _{1 outside} , when S _{1 inside} = S _{1 outside} , then the total signal amplitude generated by the primary field is:

Therefore, the output signal of the z-component receiving coil 1 is not affected by the primary field, and only has the induction output of the secondary field. When the transmitting coil 10 generates the primary field, its total field is symmetrical along its own plane. For any receiving coil that is vertical to the transmitting plane and symmetrical based on the transmitting plane, the influence of the primary field will also have the same effect as that of the z-component receiving coil 1. That is, it is offset by its own structure. Therefore, the x-component receiving coil 2 and the y-component receiving coil 3 will not be affected by the primary field.

During general flight work, the calibration coil 14 is generally in a disconnected state, that is, the eddy current generated by the transmitting coil 10 on the calibration coil is basically zero, which will not affect the actual exploration results. Once the staff needs to detect whether the whole device is working properly, they don't need to land on the ground, they only need to use the helicopter 13 to pull the device up to more than 300 meters, and at this time, the calibration coil 14 is connected, and the transmitting coil 10 emits an excitation current. The eddy current effect is generated on the calibration coil 14 , and after the transmitting coil 10 turns off the current, the magnetic field generated by the eddy current effect is received by the receiving coils 1 , 2 , and 3 , and the eddy current attenuation curve of the calibration coil can be viewed in the data recording system 7 . Since the parameters of the calibration coil 14 are known, that is, the formed eddy current attenuation curve is also known, comparing the eddy current attenuation curve obtained through the data recording system 7 with the known eddy current attenuation curve can verify whether the device works normally.

Example 2

Helicopter 13 is equipped with data collection system 7, and DC power is provided by helicopter 13, and cross-shaped bracket 9 supports transmitting coil 10, x component receiving coil 2, y component receiving coil 3 and calibration coil 14, and calibration coil 14 passes wire Connect with the data collection system 7, the upper end of the hanging rope 12 is tied to the bilge of the helicopter 13, the lower end of the hanging rope 12 is tied to the center of the cross support 9, the upper end of the hanging spoke 11 is tied to the middle part of the hanging rope 12, four More than two hanging spokes 11 lower ends are tied on the transmitting coil 10 at equal angles, and the hanging spokes 11 are unequal lengths before and after, and its length depends on the flight speed of the helicopter 13. On the transmitting coil 10, the effective area of the z-component receiving coil 1 is divided into two parts by the transmitting coil 10, the excitation magnetic field generated by the transmitting coil 10 is divided into two parts in the z-component receiving coil 1, and the total magnetic flux is equal in magnitude and opposite in direction, x The component receiving coil 2 is located at the center of the transmitting coil 10, which is perpendicular to the z component receiving coil 1 and also perpendicular to the flight direction of the helicopter 13, and the y component receiving coil 3 is perpendicular to both the z component receiving coil 1 and the x component receiving coil. Coil 2, and is orthogonal to x-component receiving coil 2, z-component receiving coil 1, x-component receiving coil 2 and y-component receiving coil 3 are connected to the preamplifier 5 via wire 4, and then connected to the data recorder via signal line 6 On the system 7, the calibration coil 14 is located in the middle of the z-component receiving coil 1, the x-component receiving coil 2 and the y-component receiving coil 3. When the receiving coil works normally, the calibration coil 14 is in an open circuit state, and when the calibration coil 14 is closed, it is used as a Standard exceptions verify that the receive coil is functioning properly. The outside of the transmitting coil 10 and the cross-shaped bracket 9 is wrapped with glass steel pipes, and the shape of the transmitting coil 10 is any regular polygon. The z-component receiving coil 1, the x-component receiving coil 2 and the y-component receiving coil 3 are all hollow structures, which are circular or regular polygonal. The z-component receiving coil 1, the x-component receiving coil 2 and the y-component receiving coil 3 are all wound with copper tape and grounded for interference shielding. Z-component receiving coil 1, x-component receiving coil 2 and y-component receiving coil 3 all adopt double-layer damping structure, z-component receiving coil 1, x-component receiving coil 2 and y-component receiving coil 3 are all made of shielded coil 15 larger than Elastic rubber strips 16 connecting three groups of cross-orthogonal coils to the inner casing are elastically connected to the coil inner casing 17, and the coil inner casing 17 is connected to the coil outer casing by elastic rubber strips 20 connected to the outer casing and the cross-orthogonal inner casing of more than three groups 19 are elastically connected, and the joints are respectively fixed with elastic rubber strip holders 18 to form. The calibration coil 14 forms an included angle of 45 degrees with the z-component receiving coil 1 , the x-component receiving coil 2 and the y-component receiving coil 3 . The opening and closing of the calibration coil 14 is at the discretion of the system operator on board the helicopter 13 .

The general expression of the magnetic field induction output signal of the receiving coil 1, 2, 3 can be expressed by the following formula:

$\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; NS</span>}\frac{\mathrm{<span\; class="notranslate">\; dB</span>}}{\mathrm{<span\; class="notranslate">\; dt</span>}}$

For the general structure of the pod-type helicopter aeronautical time-domain electromagnetic method device, the magnetic field acting on the receiving coils 1, 2, and 3 includes two parts: the magnetic field generated by the transmitting coil itself (primary field, represented by B ₁ ) and the underground The magnetic field (secondary field, represented by _B2 ) produced by the medium due to the eddy current effect, so for the receiving coils 1, 2, 3, the expression of the output signal is as follows when there is a transmitting current in the transmitting coil 10:

${\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; NS</span>}\frac{{\mathrm{<span\; class="notranslate">\; dB</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; dt</span>}}$

And when there is no transmitting current in the transmitting coil 10, its expression is then:

${\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; NS</span>}\frac{{\mathrm{<span\; class="notranslate">\; dB</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; dt</span>}}$

Since the current in the transmitting coil exceeds 200 amperes, B ₁ >> B ₂ , resulting in ε ₁ >> ε ₂ , if the primary field is not processed, in order to prevent the receiving coil 1, 2, 3 from causing the output voltage to be too large Saturation affects its normal operation, then the output signals of receiving coils 1, 2, and 3 can only be amplified by low multiples or not amplified or even attenuated, resulting in an unsatisfactory output amplitude of the secondary field signal with a small amplitude. In actual exploration work, the primary field signals of the receiving coils 1, 2, and 3 are useless, and suppressing or canceling their amplitudes is beneficial to the amplification of the secondary field signals in order to obtain an ideal secondary field signal.

When the transmitting coil 10 generates a primary field, the inner and outer sides of any arc will generate magnetic fields of equal magnitude and opposite directions, respectively denoted as B _{1 inside} and B _{1 outside} , and the z-component receiving coil 1 placed on it is divided into The two areas are respectively represented as S _{1 inside} and S _{1 outside} , when S _{1 inside} = S _{1 outside} , then the total signal amplitude generated by the primary field is:

Therefore, the output signal of the z-component receiving coil 1 is not affected by the primary field, and only has the induction output of the secondary field. When the transmitting coil 10 generates the primary field, its total field is symmetrical along its own plane. For any receiving coil that is vertical to the transmitting plane and symmetrical based on the transmitting plane, the influence of the primary field will also have the same effect as that of the z-component receiving coil 1. That is, it is offset by its own structure. Therefore, the x-component receiving coil 2 and the y-component receiving coil 3 will not be affected by the primary field.

During general flight work, the calibration coil 14 is generally in a disconnected state, that is, the eddy current generated by the transmitting coil 10 on the calibration coil is basically zero, which will not affect the actual exploration results. Once the staff needs to detect whether the whole device is working properly, they don't need to land on the ground, they only need to use the helicopter 13 to pull the device up to more than 300 meters, and at this time, the calibration coil 14 is connected, and the transmitting coil 10 emits an excitation current. The eddy current effect is generated on the calibration coil 14 , and after the transmitting coil 10 turns off the current, the magnetic field generated by the eddy current effect is received by the receiving coils 1 , 2 , and 3 , and the eddy current attenuation curve of the calibration coil can be viewed in the data recording system 7 . Since the parameters of the calibration coil 14 are known, that is, the formed eddy current attenuation curve is also known, comparing the eddy current attenuation curve obtained through the data recording system 7 with the known eddy current attenuation curve can verify whether the device works normally.

Claims (6)

1. a time domain aviation electromagnetic method primary field is from canceller, it is characterized in that, helicopter (13) is equipped with data acceptance system (7), provide direct supply by helicopter (13), cross bracket (9) supports transmitting coil (10), x component receiving coil (2), y component receiving coil (3) and alignment coil (14), alignment coil (14) is connected with data acceptance system (7) by lead, hang rope (12) upper end and tie up to helicopter (13) bilge, hang rope (12) lower end and tie up to the center of cross bracket (9), hanging spoke (11) upper end more than four ties up to and hangs rope (120 middle part, (110 lower end equal angles tie up on the transmitting coil (10) to hang spoke, it is not isometric for front and back to hang spoke (11), its length depends on the flying speed of helicopter (13), z component receiving coil (1) is contained on the transmitting coil (10) through beam (8), the useful area of z component receiving coil (1) is launched coil (10) and is divided into two parts, transmitting coil (10) is with z component receiving coil (1) separated into two parts, and excitation field total magnetic flux opposite sign but equal magnitude in two parts that receiving coil (1) is divided into that transmitting coil (10) produces, x component receiving coil (2) is positioned at the center of transmitting coil (10), both perpendicular to z component receiving coil (1), also perpendicular to the heading of helicopter (13), y component receiving coil (3) both perpendicular to z component receiving coil (1) also perpendicular to x component receiving coil (2), and with x component receiving coil (2) quadrature, z component receiving coil (1), x component receiving coil (2) and y component receiving coil (3) are connected on the prime amplifier (5) through lead (4), be connected on the data acceptance system (7) through signal wire (6) again, alignment coil (14) is positioned at the centre position of z component receiving coil (1) and x component receiving coil (2) and y component receiving coil (3), alignment coil (14) is in open-circuit condition when the receiving coil operate as normal, and alignment coil (14) is used as standard when closed and verifies unusually whether receiving coil is working properly.

According to the described time domain aviation electromagnetic method of claim 1 primary field from canceller, it is characterized in that transmitting coil (10) and cross bracket (9) outside are surrounded by glass reinforced plastic pipe, transmitting coil (10) be shaped as circle or any regular polygon.

According to the described time domain aviation electromagnetic method of claim 1 primary field from canceller, it is characterized in that z component receiving coil 1, x component receiving coil (2) and y component receiving coil (3) are hollow-core construction, are circle or regular polygon.The distance of prime amplifier (5) and three hub of a spools is greater than 2 meters, and receiving coil 1,2,3 can work independently respectively and also can two or three work simultaneously.

According to the described time domain aviation electromagnetic method of claim 1 primary field from canceller, it is characterized in that z component receiving coil 1, x component receiving coil (2) and y component receiving coil (3) all adopt copper strips to twine and carry out interference shielding in the mode of ground connection.

According to the described time domain aviation electromagnetic method of claim 1 primary field from canceller, it is characterized in that, z component receiving coil 1, x component receiving coil (2) and y component receiving coil (3) all adopt the double-layer shock-absorbing structure, z component receiving coil 1, x component receiving coil (2) is connected with coil inner casing (17) elasticity greater than the elastic rubber strip (16) that three groups of cross orthorhombic form coils are connected with inner casing with the coil (15) of y component receiving coil (3) by the band shielding, coil inner casing (17) is connected with coil case (19) elasticity by the elastic rubber strip (20) that is connected with shell greater than three groups cross orthorhombic form inner casing, and the junction adopts respectively that elastic rubber strip holder (18) is fixing to be constituted.

According to the described time domain aviation electromagnetic method of claim 1 primary field from canceller, it is characterized in that, alignment coil (14) simultaneously with z component receiving coil 1, x component receiving coil (2) and y component receiving coil (3) in angle of 45 degrees.

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