CN110658559A - Self-adaptive amplification electromagnetic measurement system and method based on polarization characteristic point amplitude ratio - Google Patents
Self-adaptive amplification electromagnetic measurement system and method based on polarization characteristic point amplitude ratio Download PDFInfo
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Abstract
The invention relates to a self-adaptive amplification electromagnetic measurement system and method based on polarization characteristic point amplitude ratio, and aims to improve the measurement precision of a nano-magnitude polarization signal in time domain electromagnetism. The measurement system includes: SQUID sensor, segmentation enlarger portion, signal acquisition portion. The specific method comprises the following steps: setting detection parameters according to geological information of a to-be-detected polarization area; based on a typical polarization model, numerically simulating attenuation curves under different turn-off times by adopting an integral equation method, defining the maximum value of positive and negative responses as a polarization characteristic point, calculating the amplitude ratio of the polarization characteristic point, and constructing a sample set; establishing a function of the ratio of the turn-off time to the amplitude value by an e-exponential fitting method, and determining the actual amplification factor of the positive and negative response stages according to the transmission current parameter; and finally, the SQUID sensor receives the secondary magnetic field, the zero-crossing comparator judges the zero point in real time, and the program-controlled amplifier amplifies the received signals in a segmented manner. Has the advantages that: the method realizes the adaptive amplification of the nano-level polarization signal and improves the detection precision of the polarization area.
Description
Technical Field
The invention relates to the technical field of geological exploration, in particular to a self-adaptive amplification electromagnetic measurement system and method based on a polarization characteristic point amplitude ratio.
Background
The Polarization effect (Induced Polarization) is an important electrochemical phenomenon, commonly found in metal ores, infested mineral resources, and water-bearing geology. The polarized medium has higher economic value, and the effective detection of the polarized medium is one of the key ways for solving the increasingly sharp contradiction between supply and demand of mineral resources. Transient electromagnetic methods (Transient electro-magnetic methods) are time domain electromagnetic detection methods based on the electromagnetic induction principle, and can effectively find water-containing geology, karst caves and channels, coal mine goafs, underground metal deposits and the like. At present, a transient electromagnetic method is used for simultaneously exploring an induction field and a polarization field and carrying out combined interpretation, the interpretation precision of the earth electrical structure can be effectively improved, and the transient electromagnetic method becomes a research hotspot and is applied to the fields of metal mine, hydrology, environmental exploration and the like.
When transient electromagnetism is used for detecting the non-polarized earth, the measured magnetic field response is unidirectionally attenuated and always has a positive value, when the polarized earth is measured, the magnetic field response curve is rapidly attenuated in the early stage, and the sign reversal phenomenon appears in the late stage. However, since the negative response occurs in the late stage of the electromagnetic response attenuation, the amplitude is about several nano-meters, compared with the non-polarized area, the amplitude of the late stage is several orders of magnitude lower, and the signal-to-noise ratio is lower, if a conventional receiver is used to directly measure the polarization signal, the negative response may be submerged in the background noise of the receiver, and is not easy to directly acquire, so that a large amount of loss of geologic body information is caused, and the negative response has become a development bottleneck of induction-polarization dual-field combined detection at present.
Chinese patent CN105676295A discloses a magnetic field measurement system with a large dynamic range and a measurement method, the system includes SQUID sensor, polarity conversion module, signal compression acquisition module, the invention realizes the magnetic field measurement problem with a large dynamic range, but does not provide a solution for the problem of polarization negative response measurement.
Chinese patent CN108227011A discloses a dual trapezoidal wave emitting system with controllable falling edge and a control method, the system obtains trapezoidal wave emitting currents with different turn-off times through transient suppression diodes with different voltages, and realizes excitation and measurement of induction field signals and polarization responses, but does not mention a solution for fine measurement of induction responses and polarization responses.
In 2018, Du et al studied the principle of polarization effect under magnetic source excitation in published papers and proposed that measuring polarization response using a low temperature SQUID sensor could effectively improve resolution, but did not analyze the influence of turn-off time on polarization characteristic points alone, nor do further studies on effective detection of negative response.
Disclosure of Invention
The invention aims to solve the technical problem of providing a self-adaptive amplification electromagnetic measurement system and method based on a polarization characteristic point amplitude ratio, and solves the problems of low polarization signal precision and the like of the conventional transient electromagnetic receiving system in the late stage of induction-polarization dual-field detection.
The invention is realized in this way, a self-adaptive amplification electromagnetic measurement system based on the amplitude ratio of the polarization characteristic points, comprising:
the SQUID sensor is used for receiving secondary field signals;
the buffer is used for buffering the signal collected by the SQUID sensor;
the program control amplifier adjusts the amplification factor to carry out differential amplification on the signals transmitted by the buffer;
the zero crossing comparator is used for identifying the zero crossing point of the signal of the SQUID sensor in real time and triggering the program control amplifier to switch the amplification factor;
and the main control module receives the signal of the program control amplifier, writes the signal into a storage medium according to a preset format specification, and controls the synchronization circuit to realize the GPS synchronization of the transmitter and the receiver.
Furthermore, after receiving the trigger signal of the zero-crossing comparator, the programmable amplifier automatically adjusts the amplification factor, and amplifies the amplitude of the negative response signal to be at the same level as the positive response amplitude.
Further, the air conditioner is provided with a fan,the magnification factor comprises a positive response stage magnification factor M1And negative response phase amplification factor M2Positive response phase magnification factor M1And negative response phase amplification factor M2The relationship between them is: m2＝P·M1Wherein P is the amplitude ratio P of the positive response to the negative response, and the initial value of the amplification factor is the amplification factor M of the positive response stage1。
Further, the magnitude ratio P of the positive response to the negative response is calculated as: the maximum value of the positive response and the maximum value of the negative response in the attenuation curve according to different turn-off times in the transmitting coil are respectively defined as a polarization characteristic point Q1Polarization characteristic point Q2Amplitude ratio P ═ Q1/Q2。
A self-adaptive amplification electromagnetic measurement method based on polarization characteristic point amplitude ratio,
acquiring geological information according to the geological profile of the region to be detected;
judging whether the region to be detected is a high-resistance region, a medium-resistance region or a low-resistance region, and determining adopted emission current parameters according to the electromagnetic field attenuation speed rule in different geological regions, wherein the emission current parameters comprise emission frequency, duty ratio, amplitude and turn-off time toff；
Laying a transmitting-receiving device, carrying out GPS synchronization, and receiving a secondary field signal by adopting a SQUID sensor;
determination of positive response magnification M by means of polarization characteristic points1And negative response magnification M2And input to the program controlled amplifier;
identifying and judging the zero crossing point of the signal of the SQUID sensor in real time according to a zero crossing comparator, and triggering a program control amplifier to switch the amplification factor;
if not, the amplification factor maintains the positive response amplification factor M1If yes, the amplification factor is switched to negative response amplification factor M2；
The amplified signal is a/D converted and stored in a preset data format.
Further, the air conditioner is provided with a fan,
determination of positive response magnification M by means of polarization characteristic points1And negative response magnification M2The method comprises the following steps: establishing a typical polarization model according to the acquired geological information, numerically simulating attenuation curves of different turn-off times by combining with parameters of a transmitting-receiving system, and defining a positive response maximum value and a negative response maximum value in the attenuation curves as polarization characteristic points Q respectively1And polarization characteristic point Q2Extracting polarization characteristic points in all attenuation curves, and calculating the amplitude ratio P-Q1/Q2Constructing an amplitude ratio sample set P ═ P1P2…Pn]；
Drawing a curve of the amplitude ratio P and the turn-off time according to the sample set, and constructing the turn-off time t by an e-exponential fitting methodoffObtaining the positive response amplification factor M of the positive and negative response stages of the secondary magnetic field according to the actual turn-off time as a function of the amplitude ratio P1And negative response magnification M2。
Further, the air conditioner is provided with a fan,
drawing t from a sample setoff-P-curve, constructing a function of the polar characteristic point amplitude ratio and the turn-off time by e-exponential fitting:
wherein a and c are fitting coefficients, b and d are exponential powers, and V is obtained by selecting full scale amplificationref＝Q1×M1＝Q2×M2Wherein V isrefObtaining the amplification factor relation M between the negative response and the positive response stage for the reference voltage of the A/D converter through equation transformation2/M1＝Q1/Q2Substituting the off-time t set in step 1 into equation (1) as PoffObtaining a P value under the excitation of actual emission current; presetting a M1The value is used as the positive response stage magnification, and the negative response stage magnification is automatically determined as M2＝P×M1。
Further, in step 2, the different turn-off times are sampled at equal intervals in the range of 1-2000 microseconds.
Compared with the prior art, the invention has the beneficial effects that:
the method comprises the steps of establishing an amplitude ratio sample set of the polarization characteristic points by numerically simulating attenuation curves at different turn-off times, establishing a relational expression between the turn-off time and the amplitude ratio of the polarization characteristic points by using an e-exponential fitting method, and adaptively adjusting the amplification times according to the set turn-off time; finally, a zero crossing comparator and a program control amplifier are adopted to realize self-adaptive amplification, negative response is amplified to the same amplitude level as positive response, the problem that a polarization signal is difficult to detect due to too small amplitude after zero crossing is solved, the signal to noise ratio of the polarization signal in a later period is effectively improved by hundreds of times, high-precision measurement of a transient electromagnetic receiving system on an induction-polarization signal is realized, and the interpretation precision of an underground abnormal body is effectively improved.
Drawings
FIG. 1 is a schematic diagram of an overall structure of a transient electromagnetic receiving system;
FIG. 2 is a general flow chart of the measurement method;
FIG. 3 is a flow chart of amplitude ratio versus off time determination;
FIG. 4 is a graph of the amplitude ratio of the polarization feature points in the high resistance region as a function of turn-off time;
FIG. 5 is a schematic diagram of the positive and negative response of a polarized dielectric electromagnetic signal;
fig. 6 is a graph comparing results of the conventional measurement system (a) and the measurement system (b).
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1, the adaptive amplification electromagnetic measurement system based on the amplitude ratio of the polarization characteristic points provided by the invention comprises a SQUID sensor 1, a segmented amplification part and a signal acquisition part.
Wherein the segmented amplifying part comprises a zero-crossing comparator 2, a data buffer 3 and a programmable amplifier 4. The signal acquisition part comprises a main control module 5, an A/D converter 6, a display module 7, a synchronization module 8, a storage medium 9, a key 10, a GPS antenna 11 and the like, wherein the SQUID sensor 1 is respectively connected with the data buffer 3 and the zero-crossing comparator 2 and then connected with the program control amplifier 4, and the output end of the program control amplifier 4 is connected with the A/D converter 6 and then connected with the main control module 5; the GPS antenna 11 is connected with the synchronization module 8, the synchronization module 8 is connected with the main control module 5 through the communication port, and the key 10, the display module 7 and the storage medium 9 are connected with the main control module through interfaces.
The receiving system is powered by a lithium battery pack and supplies power to the main control module 5, the synchronization module 8, the display module 7, the program control amplifier 4, the zero-crossing comparator 2 and the like through a DC/DC converter. The zero-crossing comparator 2 is used for judging the occurrence of negative response in real time and triggering the program-controlled amplifier 4; the program control amplifier 4 is used for realizing sectional amplification of induction-polarization response, the synchronization module 8 is used for realizing GPS synchronization of the transmitter and the receiver, the key 10 and the display module 7 form a man-machine interaction interface through the input interface and the main control module 5, and parameters such as a waveform receiving period, a sampling point number, a synchronization mode and the like are set through the man-machine interaction interface.
Transient electromagnetic induction-polarization signals in the polarized earth are in positive response in the early stage, induction fields are dominant, signals in the middle stage are rapidly attenuated, negative response occurs in the late stage, the polarization fields are dominant at the moment, the amplitude is in the range of several-dozens of nano-meters, and the transient electromagnetic induction-polarization signals are easily submerged in noise and cannot be found. Therefore, when measuring, the positive response and the negative response need to be amplified in a segmented manner, and the positive and negative response amplitudes are amplified to the same level. The signal of the SQUID sensor 1 firstly passes through the buffer 3 and the zero-crossing comparator 2 respectively, wherein the zero-crossing comparator 2 adopts a hysteresis voltage comparator, can identify the zero crossing point of the signal in real time and effectively prevent false triggering; the buffer 3 transfers the data to the program control amplifier 4 for differential amplification, and the initial amplification factor of the program control amplifier 4 is set to be M1When the signal of SQUID sensor 1 is attenuated to zero, zero-crossing comparator 2 triggers program-controlled amplifier 4 to carry out mode conversion, and the amplification factor is automatically switched to M2The amplitude of the negative response is amplified to be at the same level as the positive response amplitude, then enters the main control module 5 after passing through the A/D converter 6, and is written into the storage medium 9 according to a preset format specification.
Program controlled amplifier receptionAfter the trigger signal of the zero-crossing comparator is reached, the amplification factor can be automatically adjusted, and the amplitude of the negative response signal is amplified to be at the same level as that of the positive response signal. The magnification factor comprises a positive response stage magnification factor M1And negative response phase amplification factor M2Positive response phase magnification factor M1And negative response phase amplification factor M2The relationship between them is: m2＝P·M1Wherein P is the amplitude ratio P of the positive response to the negative response, and the initial value of the amplification factor is the amplification factor M of the positive response stage1。
Wherein the ratio of the magnitude of the positive response to the magnitude of the negative response, P, is calculated as: the maximum value of the positive response and the maximum value of the negative response in the attenuation curve according to different turn-off times in the transmitting coil are respectively defined as a polarization characteristic point Q1Polarization characteristic point Q2Amplitude ratio P ═ Q1/Q2。
Referring to fig. 2 and 3, the adaptive amplification electromagnetic measurement method based on the amplitude ratio of the polarization characteristic points provided by the invention comprises the following steps:
acquiring geological information according to the geological profile of the region to be detected;
judging whether the region to be detected is a high-resistance region, a medium-resistance region or a low-resistance region, and determining adopted emission current parameters according to the electromagnetic field attenuation speed rule in different geological regions, wherein the emission current parameters comprise emission frequency, duty ratio, amplitude and turn-off time toff；
Laying a transmitting-receiving device, carrying out GPS synchronization, and receiving a secondary field signal by adopting a SQUID sensor;
determination of positive response magnification M by means of polarization characteristic points1And negative response magnification M2And input to the program controlled amplifier;
identifying and judging the zero crossing point of the signal of the SQUID sensor in real time according to a zero crossing comparator, and triggering a program control amplifier to switch the amplification factor;
if not, the amplification factor maintains the positive response amplification factor M1If yes, the amplification factor is switched to negative response amplification factor M2；
The amplified signal is a/D converted and stored in a preset data format.
The method comprises the steps of obtaining geological data of a polarization area, roughly judging that the area is a high-resistance area, a medium-resistance area and a low-resistance area, and then determining adopted transmitting current parameters such as transmitting frequency, duty ratio, amplitude and turn-off time according to the law of electromagnetic field attenuation speed in different geology, wherein the electromagnetic field attenuation speed of the high-resistance area is fastest, a fast turn-off oblique step waveform (turn-off time is less than 500 microseconds) needs to be adopted, and the electromagnetic fields of the medium-resistance area and the low-resistance area are slowly attenuated, so that the turn-off time can. The high-power transmitter is adopted to transmit primary current, the transmitting frequency generally adopts low-frequency (lower than 25Hz) signals, the parameters of the transmitting coil can be adjusted according to the detection requirement, any turn-off time is set, and the turn-off time is toffL/R · ln2, where L and R represent the inductance and resistance of the transmitter coil, respectively. According to geological data, an experimental area is known to be a high-resistance area, the conductivity is about 0.01 Siemens/meter, therefore, in order to ensure the measurement accuracy, a rectangular transmitting loop of 100 meters multiplied by 100 meters is laid, a high-power transmitter is adopted to transmit bipolar trapezoidal waves with 6.25 Hz and 50% duty ratio, the amplitude of the transmitting current is 100 amperes, and the turn-off time t is toffThe time is 100 microseconds, and the detection requirement of the high-resistance polarization area can be fully met.
Referring to FIG. 3, the positive response magnification M is determined by the polarization feature point1And negative response magnification M2The method comprises the following steps: establishing a typical polarization model according to the acquired geological information, numerically simulating attenuation curves of different turn-off times by combining with parameters of a transmitting-receiving system, and defining a positive response maximum value and a negative response maximum value in the attenuation curves as polarization characteristic points Q respectively1And polarization characteristic point Q2Extracting polarization characteristic points in all attenuation curves, and calculating the amplitude ratio P-Q1/Q2Constructing an amplitude ratio sample set P ═ P1P2…Pn]；
Drawing a curve of the amplitude ratio P and the turn-off time according to the sample set, and constructing the turn-off time t by an e-exponential fitting methodoffObtaining positive and negative response stages of the secondary magnetic field respectively as positive response amplification factors M according to the actual turn-off time as a function of the amplitude ratio P1And negative response magnification M2。
Specifically, a typical polarization model is established according to the acquired geological information, attenuation curves with different turn-off times (within 1-2000 microseconds) are numerically simulated by combining parameters of a transmitting-receiving system, and a polarization characteristic point Q with a positive response maximum value and a negative response maximum value as a positive response maximum value in the attenuation curves is defined1Polarization characteristic point Q of negative response maximum2Extracting polarization characteristic points in all attenuation curves, and calculating the amplitude ratio P-Q1/Q2Constructing an amplitude ratio sample set P ═ P1P2…Pn]；
Setting the conductivity, the polarizability, the time constant and the dispersion coefficient of the classical polarization model parameters according to geological data, and numerically simulating attenuation curves under different turn-off times based on an integral equation method and a convolution integral method, wherein the classical high-resistance polarization parameter conductivity is 0.01 Siemens/meter, the polarizability is 0.5, the time constant is 0.01 second, the dispersion coefficient is 1, and the turn-off time is sampled at equal intervals within 1-2000 microseconds; defining the maximum amplitude of positive response in the attenuation curve, namely the value of the secondary magnetic field at the moment of complete turn-off, and defining the maximum amplitude of negative response as a polarization characteristic point Q1、Q2Extracting the polarization characteristic points Q of all attenuation curves1、Q2Calculating the amplitude ratio P ═ Q1/Q2Constructing an amplitude ratio sample set P ═ P1P2…Pn]；
On the basis of the constructed sample set, the turn-off time t is constructed by an e-exponential fitting methodoffThe function of the amplitude ratio P can adaptively determine the amplification factor M of the positive and negative response stages of the secondary magnetic field according to the actual turn-off time1、M2。
Drawing t from the sample setoffP-curve, as shown in fig. 4, the function of the polar characteristic point amplitude ratio and the turn-off time is constructed by e-exponential fitting:
in one embodiment, according to a typical high-resistance polarization model, a-328.9 and b-5.6754 × 104，c＝90.26，d＝-6.988×103。
In order to ensure the acquisition precision, the negative response and the positive response need to be amplified to the same amplitude level, and full-scale amplification is generally selected, namely V is providedref＝Q1×M1＝Q2×M2Obtaining the amplification factor relation M of the positive and negative response stages through equation transformation2/M1＝Q1/Q2P, combined transmitter off time toffDetermining the amplitude ratio P of the positive response to the negative response, thereby determining the amplification M of the second stage of the programmable amplifier2＝P·M1. In one embodiment, under the excitation of the trapezoidal wave with the turn-off time of 100 microseconds, the amplitude of the turn-off time is taken as a standard quantity Q1At this time according to Q1The value and the preset magnification factor of the receiver range are M1＝Vref200, reading the set off time according to equation (1) to obtain the amplitude ratio P of 50, thus determining the negative response stage amplification factor M2＝10000。
Amplifying the positive response by a factor M1And negative response magnification M2Writing into a programmable amplifier and assigning an initial value M1Judging the zero crossing point of the measured signal by adopting a zero crossing comparator, and switching the program control amplifier to M when the zero crossing signal is detected2If zero crossing point is not detected, keeping M1The change is not changed;
in one embodiment, the measuring field assigns an initial value M for the multiple of the programmable amplifier through a key device1At 200, as shown in fig. 5, the positive response and the negative response received by the SQUID sensor are respectively E1(t) and E2(t) the zero-crossing comparator triggers the programmable amplifier to switch to the amplification factor M when the signal crosses zero2The signals entering the receiver are respectively 200 × E1(t) and 10000 × E2(t), both close to the reference voltage V of the A/D converterrefThe range of the analog-to-digital converter is fully utilized as 5V.
And (3) carrying out actual measurement in a polymetallic ore polarization region by using a SQUID sensor, amplifying signals, carrying out A/D conversion, and storing according to a preset data format.
Selecting a central point O on a plane, carrying out actual measurement by using the SQUID sensor 2, receiving a GPS synchronous signal by a receiving control circuit in a GPS synchronous mode, synchronously transmitting and receiving time sequences, acquiring the Hz component of a central magnetic field by adopting a high-speed A/D converter 5 with the sampling rate of 2MSPS, and writing the Hz component into a storage medium according to a preset format specification. As shown in fig. 6, the comparison between the conventional measurement system and the measurement system is shown, where a is the measurement result of the conventional measurement system, and b is the measurement result of the system, it can be known that the measurement system and the method provided by the present invention can effectively improve the measurement accuracy, and increase the signal-to-noise ratio of the late polarization response by 250 times.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (8)
1. A self-adaptive amplification electromagnetic measurement system based on polarization characteristic point amplitude ratio is characterized in that: the method comprises the following steps:
the SQUID sensor is used for receiving secondary field signals;
the buffer is used for buffering the signal collected by the SQUID sensor;
the program control amplifier adjusts the amplification factor to carry out differential amplification on the signals transmitted by the buffer;
the zero crossing comparator is used for identifying the zero crossing point of the signal of the SQUID sensor in real time and triggering the program control amplifier to switch the amplification factor;
and the main control module receives the signal of the program control amplifier, writes the signal into a storage medium according to a preset format specification, and controls the synchronization circuit to realize the GPS synchronization of the transmitter and the receiver.
2. The system of claim 1, wherein the programmable amplifier receives the trigger signal from the zero-crossing comparator and automatically adjusts the amplification to amplify the magnitude of the negative response signal to the same level as the magnitude of the positive response signal.
3. According to claimThe system of claim 1, wherein the magnification factor comprises a positive response phase magnification factor M1And negative response phase amplification factor M2Positive response phase magnification factor M1And negative response phase amplification factor M2The relationship between them is: m2＝P·M1Wherein P is the amplitude ratio P of the positive response to the negative response, and the initial value of the amplification factor is the amplification factor M of the positive response stage1。
4. The system of claim 3, wherein the ratio of the magnitude, P, of the positive response to the negative response is calculated as: the maximum value of the positive response and the maximum value of the negative response in the attenuation curve according to different turn-off times in the transmitting coil are respectively defined as a polarization characteristic point Q1Polarization characteristic point Q2Amplitude ratio P ═ Q1/Q2。
5. A self-adaptive amplification electromagnetic measurement method based on the amplitude ratio of polarization characteristic points is characterized in that,
acquiring geological information according to the geological profile of the region to be detected;
judging whether the region to be detected is a high-resistance region, a medium-resistance region or a low-resistance region, and determining adopted emission current parameters according to the electromagnetic field attenuation speed rule in different geological regions, wherein the emission current parameters comprise emission frequency, duty ratio, amplitude and turn-off time toff；
Laying a transmitting-receiving device, carrying out GPS synchronization, and receiving a secondary field signal by adopting a SQUID sensor;
determination of positive response magnification M by means of polarization characteristic points1And negative response magnification M2And input to the program controlled amplifier;
identifying and judging the zero crossing point of the signal of the SQUID sensor in real time according to a zero crossing comparator, and triggering a program control amplifier to switch the amplification factor;
if not, the amplification factor maintains the positive response amplification factor M1If yes, the amplification factor is switched to negative response amplification factor M2；
The amplified signal is a/D converted and stored in a preset data format.
6. The method of claim 5,
determination of positive response magnification M by means of polarization characteristic points1And negative response magnification M2The method comprises the following steps: establishing a typical polarization model according to the acquired geological information, numerically simulating attenuation curves of different turn-off times by combining with parameters of a transmitting-receiving system, and defining a positive response maximum value and a negative response maximum value in the attenuation curves as polarization characteristic points Q respectively1And polarization characteristic point Q2Extracting polarization characteristic points in all attenuation curves, and calculating the amplitude ratio P-Q1/Q2Constructing an amplitude ratio sample set P ═ P1P2…Pn]；
Drawing a curve of the amplitude ratio P and the turn-off time according to the sample set, and constructing the turn-off time t by an e-exponential fitting methodoffObtaining the positive response amplification factor M of the positive and negative response stages of the secondary magnetic field according to the actual turn-off time as a function of the amplitude ratio P1And negative response magnification M2。
7. The method of claim 6,
drawing t from a sample setoff-P-curve, constructing a function of the polar characteristic point amplitude ratio and the turn-off time by e-exponential fitting:
wherein a and c are fitting coefficients, b and d are exponential powers, and V is obtained by selecting full scale amplificationref＝Q1×M1＝Q2×M2Wherein V isrefObtaining the amplification factor relation M between the negative response and the positive response stage for the reference voltage of the A/D converter through equation transformation2/M1＝Q1/Q2Substituting the off-time t set in step 1 into equation (1) as PoffObtaining a P value under the excitation of actual emission current; presetting a M1The value is used as the positive response stage magnification, and the negative response stage magnification is automatically determined as M2＝P×M1。
8. The method of claim 6, wherein in step 2, the different off times are sampled at equal intervals in the range of 1-2000 microseconds.
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| CN113252997A (en) * | 2021-06-28 | 2021-08-13 | 成都点阵科技有限公司 | Control method of frequency-selecting type electromagnetic radiation monitor |
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