36 results about "Proton magnetometer" patented technology

The invention aims to provides a measuring device and method suitable for a non-orthogonal angle between saddle-shaped coil X and Y axes of an SERF atom magnetometer, and belongs to the technical fields of optical detection, weak magnetic detection and uniform magnetic field coils. Aimed at the problem that non-orthogonality of three-dimensional magnetic coils influences the sensitivity of the SERF atom spin magnetometer, the measuring method and device of the non-orthogonal angle between the saddle-shaped coil X and Y axes, which are based on Bloch kinetic equations, are provided. The invention fills in the blanks of the measuring method and device of the non-orthogonal angle between the saddle-shaped coil X and Y axes of the atom magnetometer, effective references are provided for the atom magnetometer to estimate and compensate a magnetic field deviation value, and the improvement of the sensitivity of the SERF atom magnetometer is ensured.

The invention relates to an aeromagnetic measuring device and method based on a fixed-wing unmanned aerial vehicle. The aeromagnetic measuring device comprises the fixed-wing unmanned aerial vehicle, a proton magnetometer and a flight control system. A measuring holder used for installation of the proton magnetometer is fixed to the fixed-wing unmanned aerial vehicle. The proton magnetometer is used for carrying out magnetic measurement in the flying process of the fixed-wing unmanned aerial vehicle, and transmitting the magnetic measurement data to the flight control system. The flight control system is used for collecting flight data of the fixed-wing unmanned aerial vehicle, receiving the magnetic measurement data transmitted by the proton magnetometer, and sending the flight data and the magnetic measurement data to the ground in real time, so that flying control over the fixed-wing unmanned aerial vehicle is achieved on the ground according to the received flight data. The aeromagnetic measuring device and method solve the problems that manned vehicle aeromagnetic measurement is high in operation cost and personnel risk, and ground magnetic measurement is low in operation efficiency, large in environmental disturbance and the like.

A magnetometer which is composed of digitization frequency-selecting amplifier circuit, digital control current source, single chip computer, clock circuit, communication circuit and relevant control software applies measuring method of frequency in equal period frequency division to carry on measurement for magnetic field intensity according to prin ciple of proton precession. It can carry out measurement for multitype component conbination of F, Z, H, Fe, FH, FHD and FZD under the condition of manual operation or automatic operation according to the setting and it can carry out some other functions based on above principle.

The invention relates to the technical field of magnetic field measurement, in particular to a magnetometer capable of absolutely measuring a weak magnetic field. The magnetometer comprises a high-frequency oscillator (1), a probe (2), a DC pulse generator (3), an amplifier (4), a frequency meter (5) and a numerical control unit (6); the numerical control unit (6) controls all parts to work in a coordinative way to form the high-precision OVERHAUSER proton magnetometer; and an external magnetic filed is measured through the mutual action of double resonance systems, i.e. resonance of unpaired electrons of free radical in free radical solution in the probe in a high-frequency magnetic field and resonance of protons in the free radical solution in the external magnetic field. The OVERHAUSER magnetometer has the advantages of high precision, high sensitivity, low power consumption, absolute measurement to the external magnetic field and the like.

The invention relates to the field of magnetic measurement and, more particularly, to an error calibration method for a geomagnetic vector measurement system based on a Lagrange multiplier method. The error calibration method comprises the steps of (S1) selecting a calibration area, setting a non-magnetic platform at the center of the area, and measuring the total amount of the geomagnetic field above the non-magnetic platform with a proton magnetometer; (S2) encapsulating a geomagnetic vector measurement system in a non-magnetic L-face box, and placing the box on a non-magnetic surface; (S3) turning over and placing the non-magnetic L-faced box on the non-magnetic platform successively with each side as a bottom surface, when each face is used as the bottom surface, rotating the L-faced box around the vertical axis of the non-magnetic platform under uniform angle differences for R attitudes, and recording output values of a three-axis magnetic sensor and an inertial navigation system at each attitude; and (S4) establishing a linear system of equations with the total amount of the geomagnetic field as a constraint for joint solution to obtain comprehensive error model parameters and further obtaining a geomagnetic vector value under a geometrical coordinate system and a magnetic sensor coordinate system after calibration.

The invention discloses a mobile platform magnetic gradient tensor system correction method, which comprises the following steps: S1, a single sensor system error is modeled; S2, a compensation modelis established for the single sensor system error; S3, a magnetic gradient tensor system is made to change the attitude randomly for data acquisition in three-dimensional space, and a proton magnetometer is used to measure the total magnetic field in the experiment environment; and S4, with the total magnetic field in the experiment environment as a standard, the data acquired by a fluxgate sensorare inverted to obtain system error parameters of the sensor. The correction method used in the invention is free from the dependence on a high-precision three-axis rotary table, random attitude fordata acquisition in the three-dimensional space can be carried out, the method is convenient and easy, the influences on the correction result by errors of the three-axis rotary table can be eliminated, the inversion precision is high, the simulation result shows that the system error parameter estimation error can reach a level of one thousandth, the correction precision of the magnetic gradienttensor system can be greatly improved, and the performance of the magnetic gradient tensor system is improved.

A method for measuring a triaxial magnetic field coil quadrature angle is disclosed. A magnetic field with a certain size is generated in a triaxial magnetic field coil. A value of a magnetic induction intensity amount can be read through equipment which is used to measure the magnetic induction intensity amount. And then an included angle between the coils can be calculated through a formula. The equipment of measuring the magnetic induction intensity amount is an optical pump or a proton magnetometer. By using the method provided in the invention, equipment movement and installation operation are not needed during measuring the quadrature angle of the triaxial coil; a horizontal state is not needed to be aligned and be searches; machinery assembling operation is not needed so that an installation error can be avoided. The method possesses advantages of high precision measurement, simple operation and the method is easy and convenient to be used. If the method is used to measure the quadrature angle of the magnetic field coil of a certain apparatus, the actual measured angle is 89.82 DEG and precision can reach 0.01DEG which is an order of magnitude higher than the precision (generally 0.1 DEG) reached by using a common detection method.

The invention discloses an unmanned aerial vehicle-based marine aeromagnetic daily variation station and a geomagnetic measurement method. The daily variation station comprises an unmanned aerial vehicle flight control system, a main control system and a ship-borne device arranged on a deck of a survey ship and a geomagnetic device arranged on the unmanned aerial vehicle, wherein the geomagnetic device comprises a crossbar, and a proton magnetometer, an airborne power converter and a data acquisition memory arranged on the crossbar according to a weight ratio; the unmanned aerial vehicle flight control system communicates mutually with the unmanned aerial vehicle; the unmanned aerial vehicle flight control system is used for controlling compensation flight, position adjustment and spot hover of the unmanned aerial vehicle; and the main control system communicates with the unmanned aerial vehicle flight control system, the ship-borne device and the geomagnetic device. A mode of adoptingthe proton magnetometer loaded on the unmanned aerial vehicle and the unmanned aerial vehicle flight control system to control compensation flight, position adjustment and spot hover of the unmannedaerial vehicle is adopted, the limitations of the existing far-sea geomagnetic daily variation observation station are overcome, and the measurement precision requirements of the far-sea geomagnetic daily variation observation station are met.

The invention discloses a method for optimization selection of a proton magnetometer matching capacitor, and belongs to the technical field of magnetic field intensity detection. The method for optimization selection of the matching capacitor comprises the processes of determining matching circuit system parameters, determining the fixed minimum capacitance Cmin and gradually determining the matching capacitor. The method for optimization selection of the matching capacitor according to the matching circuit bandwidth is provided under the condition that certain frequency points are not located within the bandwidth of a matching circuit due to limited capacitor combination and matching, and the whole matching circuit bandwidth can cover the whole system bandwidth. Meanwhile, the matching method for the circuit with capacitance errors is obtained through analysis under the condition that the errors exist between actual capacitance and ideal capacitance, and the problem that due to matching frequency emission offset caused by the capacitor capacitance value errors, certain frequency points are not within the circuit bandwidth range is solved. According to the method, the matching capacitor can be selected according to different measuring ranges, and the precision of later measuring signals is improved.

The invention discloses a multi-parameter measuring proton magnetometer. The multi-parameter measuring proton magnetometer comprises a magnetometer body and a probe. A panel of the magnetometer is sequentially provided with a key region, a display screen and a GPS plug used for being connected with a GPS probe; a microcomputer board, a shielding board, an amplifying board and a battery are sequentially arranged in the magnetometer body from top to bottom; a battery plug, a USB plug and a serial port plug are sequentially arranged on the lateral side of the magnetometer body, wherein the battery plug and the USB plug are respectively connected with the microcomputer board, and the serial port plug is connected with the amplifying board; the probe comprises a probe rod, a proton probe and a fluxgate probe, wherein the proton probe is fixed to the probe rod and is used for measuring the total field of the ground, the fluxgate probe is used for measuring a three-component magnetic field, magnetic declinations and magnetic inclinations, and the proton probe and the fluxgate probe are respectively connected with the microcomputer board of the magnetometer body. The multi-parameter measuring proton magnetometer can measure a plurality of parameters in one measuring point position, namely, the total field of the ground is measured, besides, the three-component magnetic field, the magnetic declinations and the magnetic inclinations can be measured.

The invention relates to a probe of a proton magnetometer, which includes an electric field shield, two coils, and solution containing rich hydrogen protons. The solution is poured into the electric field shield. The two coils are reversely connected in series and immersed in the solution. The two ends of the coils are arranged outside the electric field shield. When the probe is used, the coils are powered on to generate a magnetic field, which can make the hydrogen protons in the solution arranged orderly in one direction. Then, the coils are powered off, and the hydrogen protons rotate in the direction of the terrestrial magnetic field. As the rotation frequency of the hydrogen protons is proportional to the intensity of the terrestrial magnetic field, the intensity of the terrestrial magnetic field can be measured by measuring the rotation frequency of the hydrogen protons.

The invention provides a nuclear magnetic resonance FID signal noise suppression method based on multilinear singular value tensor decomposition, and the method comprises the steps: obtaining a multi-channel signal: enabling one channel to start sampling at an interval of delta t through delay sampling, and obtaining the multi-channel signal; converting each channel signal into a Hankel matrix, forming a third-order tensor, performing Tucker decomposition and processing on the third-order tensor to obtain a third-order tensor, recovering the third-order tensor into a multi-channel signal, performing CP tensor decomposition processing on a second-order tensor X formed by the multi-channel signal, and finally obtaining a high signal-to-noise ratio signal xnew after fusion of multiple communication signals. The method has the advantages that the limitation of a current algorithm under strong noise interference is effectively overcome, meanwhile, the instantaneity and universality of the algorithm are guaranteed, the method can be suitable for instruments such as a proton magnetometer and a nuclear magnetic resonance water exploration instrument, the frequency domain measurement precision and the hydrological parameter accuracy of the instruments are improved, and the precision and accuracy of related geosciences are effectively improved.

The invention discloses an identification method for detecting a grouting diffusion range based on a proton magnetometer, which is suitable for underground engineering construction. In the grouting stage, firstly, superfine iron powder is added into slurry to be mixed and stirred, so that the superfine iron powder is evenly distributed in the slurry, and then the slurry mixed with the superfine iron powder is magnetized and then injected into a surrounding rock body through a permanent magnetic field formed in a magnetizing device; in the detection stage, metal detectors are arranged on the top and two sides of a roadway, a proton magnetometer is connected, and the proton magnetometer is used for observing the distribution condition of different magnetic fields in the surrounding rock body, so that the diffusion range of the slurry in the surrounding rock body is determined. The method has the advantages of being convenient to operate, economical, applicable, safe, rapid, three-dimensional and visual.

The invention discloses a blasting displacement measuring method and a magnetic target device for measurement. A magnetic target device electrified intermittently is put in an auxiliary hole. After the magnetic target device is electrified, the magnetic target device will generate a local magnetic field at the placement position to disturb the geomagnetic field value at the placement position of amagnetic target, and an interference field will be formed around the magnetic target. The magnetic field intensity of the current area before and after the placement of the magnetic target is obtained by a high-precision proton magnetometer, and data export and diurnal variation correction are carried out by the preprocessing software of the proton magnetometer. A diurnal variation station is setin the magnetic field area to carry out diurnal variation correction on the magnetic field intensity data of a blasting area, the corrected magnetic field intensity data of the blasting site before and after blasting is obtained, the magnetic anomaly of the blasting area is calculated, and a magnetic anomaly magnetic field intensity contour map is drawn. A large number of closed magnetic field intensity contour lines appear in the magnetic anomaly magnetic field intensity contour map, and the position of the magnetic target is thus determined. The positions of the magnetic target before and after blasting are located, and the blasting displacement is measured and calculated according to the positions of the magnetic target before and after blasting.

The invention provides a method and a circuit for improving the measurement precision of a proton magnetometer; the method adopts 1) a high-speed device cycle-measuring method which uses the period of the signal to be measured as the counting gate time of the standard pulse so as to calculate the period of the signal to be measured; 2) an evaluation and processing method for grade of real-time signal data, which automatically calculates the discreteness according to the difference of the magnetic field to be measured and the interference on the time domain characteristic and the attenuation characteristic of the spinning signal; and 3) a correction method for the temperature coefficient of devices, which adopts high-sensitiveness temperature integration sensor and an A / D (analog to digital) converter to directly carry out the correction in the measurement program. The circuit comprises an omni-directivity deep-sea proton magnetic probe, a probe polarization converter, a polarization controller, a tuning matcher, a frequency selective amplifier, a signal shaper, a signal counter, a counting gate, a standard pulse generator and a binary counter.

The invention discloses a marine geomagnetic daily variation observation device and a geomagnetic measuring method. The device comprises an observation boat and a plurality of floating main bodies arranged on the observation boat, wherein geomagnetic equipment is mounted on each floating main body; each floating main body comprises a positioning device, a driving device, a wireless communication device, a data processing device, a storage device and a power supply device; a control center is arranged on the observation boat; and the control center comprises a wireless communication unit, a data processing unit, a storage unit and an alarm device. The floating main bodies are launched in deep seas on latitude to be measured, and data collection is carried out on a geomagnetic field on the latitude without taking the observation boat as a carrier after magnetic field interference information of the floating main bodies is collected by a proton magnetometer, the observation is not restricted by an observation point, and the floating main bodies are quickly launched to a plurality of observation points, so that the efficiency of data collection is improved greatly.

The invention discloses a multi-parameter measuring proton magnetometer. The multi-parameter measuring proton magnetometer comprises a magnetometer body and a probe. A panel of the magnetometer is sequentially provided with a key region, a display screen and a GPS plug used for being connected with a GPS probe; a microcomputer board, a shielding board, an amplifying board and a battery are sequentially arranged in the magnetometer body from top to bottom; a battery plug, a USB plug and a serial port plug are sequentially arranged on the lateral side of the magnetometer body, wherein the battery plug and the USB plug are respectively connected with the microcomputer board, and the serial port plug is connected with the amplifying board; the probe comprises a probe rod, a proton probe and a fluxgate probe, wherein the proton probe is fixed to the probe rod and is used for measuring the total field of the ground, the fluxgate probe is used for measuring a three-component magnetic field, magnetic declinations and magnetic inclinations, and the proton probe and the fluxgate probe are respectively connected with the microcomputer board of the magnetometer body. The multi-parameter measuring proton magnetometer can measure a plurality of parameters in one measuring point position, namely, the total field of the ground is measured, besides, the three-component magnetic field, the magnetic declinations and the magnetic inclinations can be measured.

The invention discloses a geomagnetic detection method for a submarine cable, and relates to the technical field of submarine detection. The method is applied to a detection control end, and comprises the steps of S01 controlling an underwater robot provided with a proton magnetometer to perform preliminary detection, and determining preliminary cable trend and preliminary position information; S02 according to the preliminary position information, controlling an underwater robot provided with a proton magnetometer and two fluxgate magnetometers to enter water, based on a geomagnetic total field, controlling the underwater robot to drive to the position above the cable, and determining specific position information of the cable; based on an X-axis component gradient value obtained by the fluxgate magnetometers, controlling the heading direction of the underwater robot to move along the trend of the preliminary cable; S03 according to the specific position information, controlling the underwater robot provided with the proton magnetometer and two fluxgate magnetometers to enter water; and based on the Z-axis component value of the geomagnetic total field and the underwater depth data of the underwater robot, judging whether the submarine cable has a fault and the position of a fault point. The method is accurate in detection and simple to implement.

The invention provides a method and a circuit for improving the measurement precision of a proton magnetometer; the method adopts 1) a high-speed device cycle-measuring method which uses the period of the signal to be measured as the counting gate time of the standard pulse so as to calculate the period of the signal to be measured; 2) an evaluation and processing method for grade of real-time signal data, which automatically calculates the discreteness according to the difference of the magnetic field to be measured and the interference on the time domain characteristic and the attenuation characteristic of the spinning signal; and 3) a correction method for the temperature coefficient of devices, which adopts high-sensitiveness temperature integration sensor and an A / D (analog to digital) converter to directly carry out the correction in the measurement program. The circuit comprises an omni-directivity deep-sea proton magnetic probe, a probe polarization converter, a polarization controller, a tuning matcher, a frequency selective amplifier, a signal shaper, a signal counter, a counting gate, a standard pulse generator and a binary counter.

The invention discloses a locating and harmless recycling method for a polychlorinated biphenyl capacitor stored in a sealed manner. The locating and harmless recycling method comprises the following steps: (1) carrying out magnetic survey on the ground through a proton magnetometer; (2) carrying out fixed section scanning measurement through a Wenner device by taking a section line as a unit; (3) carrying out drilling sampling through a drill or a Luoyang shovel, drawing a PCBs content contour map, and determining a sealed storage position of the polychlorinated biphenyl capacitor; and (4) clearing away soil around the sealed storage position according to a sequence from inside to outside. According to the locating and harmless recycling method, equipment is simple, and the treatment speed is high; and the sealed storage position is located by using a method combining a high-precision magnetic method and a high-density electrical method, so that the position is accurately and quickly located, the treatment time is short, thorough treatment is achieved, and no high-pollution residue is retained.

A method for measuring a triaxial magnetic field coil quadrature angle is disclosed. A magnetic field with a certain size is generated in a triaxial magnetic field coil. A value of a magnetic induction intensity amount can be read through equipment which is used to measure the magnetic induction intensity amount. And then an included angle between the coils can be calculated through a formula. The equipment of measuring the magnetic induction intensity amount is an optical pump or a proton magnetometer. By using the method provided in the invention, equipment movement and installation operation are not needed during measuring the quadrature angle of the triaxial coil; a horizontal state is not needed to be aligned and be searches; machinery assembling operation is not needed so that an installation error can be avoided. The method possesses advantages of high precision measurement, simple operation and the method is easy and convenient to be used. If the method is used to measure the quadrature angle of the magnetic field coil of a certain apparatus, the actual measured angle is 89.82 DEG and precision can reach 0.01DEG which is an order of magnitude higher than the precision (generally 0.1 DEG) reached by using a common detection method.

The invention relates to the field of magnetic measurement and, more particularly, to an error calibration method for a geomagnetic vector measurement system based on a Lagrange multiplier method. The error calibration method comprises the steps of (S1) selecting a calibration area, setting a non-magnetic platform at the center of the area, and measuring the total amount of the geomagnetic field above the non-magnetic platform with a proton magnetometer; (S2) encapsulating a geomagnetic vector measurement system in a non-magnetic L-face box, and placing the box on a non-magnetic surface; (S3) turning over and placing the non-magnetic L-faced box on the non-magnetic platform successively with each side as a bottom surface, when each face is used as the bottom surface, rotating the L-faced box around the vertical axis of the non-magnetic platform under uniform angle differences for R attitudes, and recording output values of a three-axis magnetic sensor and an inertial navigation system at each attitude; and (S4) establishing a linear system of equations with the total amount of the geomagnetic field as a constraint for joint solution to obtain comprehensive error model parameters and further obtaining a geomagnetic vector value under a geometrical coordinate system and a magnetic sensor coordinate system after calibration.

The invention belongs to the technical field of drilling position detection, and discloses a method for identifying a drilling remaining sleeve based on high-precision magnetic method measurement. Themethod comprises the following steps of determining the previous excavation condition and the excavation position in a large range; determining the specific position of the drilling through daily change measurement and movement measurement; performing modeling analysis on the sleeve, and analyzing the relationship between the ground magnetic induction intensity and the model volume; performing actual measurement analysis; and performing analysis in combination with different actual conditions, and further determining the existence position of the magnetic body. According to the method, two high-precision proton magnetic instruments are used for measurement; the position of the drilling remaining sleeve is determined in a large range for measurement; the range is narrowed, meanwhile, afterthe range is further narrowed, a model is manufactured, simulation measurement is conducted, field measurement is conducted after simulation is completed, the drilling remaining sleeve is rapidly found out by determining the induction relation between the magnetic induction intensity and the magnetic body buried in the ground, the searching efficiency is high, and the precision is high.

The invention discloses a method for optimization selection of a proton magnetometer matching capacitor, and belongs to the technical field of magnetic field intensity detection. The method for optimization selection of the matching capacitor comprises the processes of determining matching circuit system parameters, determining the fixed minimum capacitance Cmin and gradually determining the matching capacitor. The method for optimization selection of the matching capacitor according to the matching circuit bandwidth is provided under the condition that certain frequency points are not located within the bandwidth of a matching circuit due to limited capacitor combination and matching, and the whole matching circuit bandwidth can cover the whole system bandwidth. Meanwhile, the matching method for the circuit with capacitance errors is obtained through analysis under the condition that the errors exist between actual capacitance and ideal capacitance, and the problem that due to matching frequency emission offset caused by the capacitor capacitance value errors, certain frequency points are not within the circuit bandwidth range is solved. According to the method, the matching capacitor can be selected according to different measuring ranges, and the precision of later measuring signals is improved.

When the vector proton magnetometer measures different components of the geomagnetic field, the signal strength will be different, and at the same time, the frequency selection circuit will have temperature drift changes, which will affect the measurement accuracy of the instrument. To solve these problems, the present invention has invented an automatic adjustment The method of intelligent frequency selection of the vector proton magnetometer based on the amplification factor of the signal amplification circuit and the frequency selection characteristics of the frequency selection circuit. This method first selects and amplifies the signal according to the frequency selection parameters and amplification factors set by the instrument, and then measures the signal. According to the strength of the signal, adjust the magnification of the frequency selection circuit to make the signal strength in a more suitable strength range, and fine-tune the frequency selection capacitance of the frequency selection circuit to make the next frequency selection signal close to the strongest and achieve accurate selection. frequency and amplification purposes. The realization circuit of the present invention is composed of four parts: a frequency selection circuit, a signal amplification circuit, a signal filter circuit, a signal strength detection circuit and a single-chip microcomputer control circuit.

The invention discloses a geomagnetic field component measuring method and a full-parameter marine geomagnetic diurnal variation station. The full-parameter marine geomagnetic diurnal variation station comprises a proton magnetometer, a fluxgate sensor, an inclination sensor, a sleeve and a directional empennage; the directional empennage is connected with the sleeve through a hoop; the proton magnetometer, the fluxgate sensor and the inclination sensor are all arranged in the sleeve; the proton magnetometer is used for measuring the total amount of the geomagnetic field; and the fluxgate sensor and the inclination sensor are used for measuring the component of a geomagnetic field. According to the invention, the proton magnetometer is arranged, so the total amount of the geomagnetic fieldcan be accurately measured; the fluxgate sensor is combined with the inclination sensor to measure the component of the geomagnetic field; and in addition, the directional empennage is additionally arranged outside the sleeve and can properly adjust the posture of the sleeve, so that the sleeve is always in an incident flow state in the ocean, the rotation of the proton magnetometer in the measurement direction is effectively reduced, and the measurement of the proton magnetometer is more stable.

The invention discloses a frequency estimation method for free induction decay signal of proton magnetometer based on IpDFT. The proton magnetometer type quantum weak magnetic measurement instrument is the most ancient instrument and has become one of the most widely used geomagnetic measurement instruments for the half century due to the advantages of simplicity in operation, good stability and the like. The precision of a derived magnetic field is determined by the precision of free induction decay signal frequency measurement in the proton magnetometer. Therefore, the method has important significance for research on high-precision frequency estimation. According to the method provided by the invention, estimation precision of the algorithm is improved, the signal frequency can be estimated within a short time, and in the environment with a low signal-to-noise ratio, higher estimation accuracy is still achieved.

Aiming at the problem that the measuring accuracy of a vector proton magnetometer is influenced since the signal strength differs when the vector proton magnetometer is used for measuring different components of a geomagnetic field and a frequency selection circuit has temperature drift change, the invention discloses an intelligent frequency selection method for a vector proton magnetometer, which can automatically adjust the amplification factor of a signal amplification circuit and the frequency selection characteristic of the frequency selection circuit. According to the method, frequencyselection and amplification are performed on a signal according to a frequency selection parameter and an amplification factor set by the vector proton magnetometer firstly, then the signal strength of the signal is measured, and the amplification factor of a frequency selection circuit is adjusted according to the strength of the signal, so that the signal strength is within a relatively appropriate strength range. Moreover, the frequency selection capacitance of the frequency selection circuit is finely adjusted, so that a next frequency selection signal is almost strongest, and the aims ofaccurate frequency selection and amplification are fulfilled. An implementation circuit consists of a frequency selection circuit, a signal amplification circuit, a signal filtering circuit, a signalstrength detection circuit and a single-chip microcomputer control circuit.

An underground optical cable detection system and a magnetic gradient detection method belong to the field of underground optical cable detection. Constant direct current is supplied to the underground long straight optical cable, and the generated magnetic field is a static magnetic field which is perpendicular to the current direction and attenuates along with increasing of the distance from the wire; the method comprises the following steps: connecting two magnetic probes through a connecting rod, connecting the magnetic probes with a proton magnetometer to form a magnetic gradient mode, measuring the magnetic induction intensities B1 and B2 of a static magnetic field, importing received data into a computer, and determining the plane position and the burying depth of the buried optical cable according to the change rule of the two magnetic probes along with the distance; the magnetic gradient method can counteract daily variation and external environment interference, so that the difference value delta of the magnetic induction intensity B is only related to the distance between the optical cable and the magnetic probe, and the more accurate burying position of the pipeline is obtained; the magnetic gradient method underground optical cable detection system can precisely position the plane position and the burial depth of the underground burial optical cable in a refined manner, and has important significance on management, planning and daily maintenance and detection of the optical cable and various underground pipelines.

The invention discloses a blasting displacement measuring method and a magnetic target device for measurement. A magnetic target device electrified intermittently is put in an auxiliary hole. After the magnetic target device is electrified, the magnetic target device will generate a local magnetic field at the placement position to disturb the geomagnetic field value at the placement position of amagnetic target, and an interference field will be formed around the magnetic target. The magnetic field intensity of the current area before and after the placement of the magnetic target is obtained by a high-precision proton magnetometer, and data export and diurnal variation correction are carried out by the preprocessing software of the proton magnetometer. A diurnal variation station is setin the magnetic field area to carry out diurnal variation correction on the magnetic field intensity data of a blasting area, the corrected magnetic field intensity data of the blasting site before and after blasting is obtained, the magnetic anomaly of the blasting area is calculated, and a magnetic anomaly magnetic field intensity contour map is drawn. A large number of closed magnetic field intensity contour lines appear in the magnetic anomaly magnetic field intensity contour map, and the position of the magnetic target is thus determined. The positions of the magnetic target before and after blasting are located, and the blasting displacement is measured and calculated according to the positions of the magnetic target before and after blasting.