CN102854537B - A kind of digital quick tracking helium light pump magnetic apparatus - Google Patents
A kind of digital quick tracking helium light pump magnetic apparatus Download PDFInfo
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- CN102854537B CN102854537B CN201210337582.3A CN201210337582A CN102854537B CN 102854537 B CN102854537 B CN 102854537B CN 201210337582 A CN201210337582 A CN 201210337582A CN 102854537 B CN102854537 B CN 102854537B
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Abstract
The present invention relates to a kind of digital quick tracking helium light pump magnetic apparatus, it is primarily of (31), high-speed ADC conversion (32), Programmable logic design (42), DAC (43), MCU (38), keyboard detection (39), liquid crystal display (37) composition.It is high that described magnetometer not only possesses tracking accuracy, the advantage that real-time is good, and the antijamming capability simultaneously also having possessed digital programmable is strong, be easy to debugging, not temperature influence, cost is low, low in energy consumption, volume is little advantage.
Description
Technical field
The present invention relates to magnetic exploration field, specifically, the present invention relates to a kind of digital quick tracking helium light pump magnetic apparatus.
Background technology
Magnetic exploration is significant for fields such as geophysical research, military and national defense, interplanetary probe, mineral reserve detections, and magnetic exploration technology was developed so far from last century, experienced by from simple to complex, by the process of simple mechanical type principle to modern electronic technology.
Magnetic exploration system, by its inner structure and principle of work, can be divided into substantially:
1) mechanical type magnetometer: as suspension wire magnetometer, utilize the bar magnet being suspended in suspension central authorities to be subject to the moment loading of vertical magnetic field intensity power, gravity and suspension torsion, measure magnetic field size, its principle is simple, processing ease.
2) electronic type magnetometer, as proton magnetometer, optically pumped magnetometer, flux-gate magnetometer etc., utilize probe sensor that magnetic field intensity is converted to electric signal, in conjunction with modern electronic technology to Electric signal processing, feedback and display, its speed and precision comparatively mechanical type improve a lot, and reading is also very convenient.
The leading indicator of magnetic exploration system has sensitivity, precision, accuracy, degree of stability, ranging scope etc.
Sensitivity refers to also can be referred to as resolution by the magnetic field minimum change (susceptibility) that magnetic exploration system can be measured; Precision weighs the index of instrument repeatability, refers to and the minimum possible value that instrument self mensuration magnetic field can reach represented, be also called self repeatable accuracy by the mean deviation of one group of measured value and mean value; Accuracy refers to the ability of Instrument measuring true value, the total error namely compared with true value.
Except These parameters, power consumption, volume, cost etc. also because considering exploration system.
Helium light pump magnetic apparatus is that the one grown up the 1950's has highly sensitive magnetic survey equipment, is to produce in magnetic field based on Zeeman effect by the atomic energy level of element, utilizes optical action and mr techniques to develop.Helium light pump magnetic apparatus is the highly sensitive magnetic exploration system after proton magnetometer, both can be used to measure magnetic field total amount, also can measure magnetic field gradient, and during measurement, inferred-zero drift, does not need strict orientation, only need during measurement magnetic survey probe and magnetic direction almost parallel.
The current helium light pump magnetic apparatus extensively come into operation mainly contains two classes from next point of circuit structure, one class is the exploration system based on mimic channel, its measuring speed is fast, but stability and precision are not high, another kind of is based on monolithic processor controlled exploration system, there is higher stability and high precision, but owing to adopting software point by point scanning resonant frequency, its measuring speed is slower.Along with the precision of the fields such as modern military technology, mineral reserve detection to magnetic-field measurement, the requirement of the index such as stability and speed, existing magnetic exploration system can not meet the demands.In this case, design a kind of novel helium light pump magnetic apparatus and there is very large commercial value, the characteristic that analog magnetometer is measured at a high speed can be taken into account simultaneously, and based on the stability of monolithic processor controlled magnetometer and high precision.
Existing up-to-date analog helium light magnetometer is divided into again auto-excitation type and tracking mode two kinds of structures, and technology related to the present invention is tracking helium optically pumped magnetometer, its structure and measuring principle as shown in Figure 1,
As shown in Figure 1, tracking helium optically pumped magnetometer is primarily of a: probe 11, for detecting magnetic field and returning electric signal, for the process of rear class measure loop; B: by selective frequency amplifier circuit 12, phase-sensitive detection circuit 13, integrating circuit 19, the measure loop that voltage controlled oscillator 16 grade is formed, for the treatment of the electric signal that probe 11 exports, and the change in locking magnetic field realizes automatic tracing and measuring; Frequency multiplier circuit 17, frequency counter 18, for when the system is stable, only need measure the centre frequency of voltage controlled oscillator 16, magnetic field size can be calculated according to following formula:
T(nT)=0.0356843f(HZ)
Existing up-to-date tracking helium light magnetometer, owing to adopting mimic channel to form hardware closed-loop measuring system, its measuring speed is very fast.But the shortcoming of mimic channel is, poor stability, easily by the impact of the factor such as temperature, power supply ripple, be difficult to accomplish high-acruracy survey.And due to exploration system input loop adopt discrete component realize, this type magnetometer is bulky, and power consumption is high, and cost is high, rigging up and debugging and scaling difficulty.Whole system magnetic survey scope is wideless, when changes of magnetic field is comparatively large, and the easy losing lock of automatic tracing and measuring system.
A kind of helium light pump magnetic apparatus up-to-date in prior art, be as shown in Figure 2 based on monolithic processor controlled exploration system.
As shown in Figure 2, probe output.The frequency that single-chip microcomputer is outputed signal by bus marco Direct Digital Frequency Synthesizers DDS24, output signal and promote incentive probe sensor 21 through power, sensor exports DC voltage, after process and AD sampling, is converted to digital signal and feeds back to single-chip microcomputer 23 again.Single-chip microcomputer 23 progressively modulates the frequency of DDS24 signal according to the DC voltage recorded, and when the DDS24 output signal being modulated to certain Frequency point makes inner generation magnetic resonance of popping one's head in, it is minimum that the probe that now single-chip microcomputer 23 records exports DC voltage.According to above-mentioned formula, utilize the frequency of now signal, magnetic field size can be calculated.Frequency sweeping stepping is less, can obtain the measurement result that precision is higher.
The magnetic exploration system of this type, adopt measurement and the tracking of Single-chip Controlling whole system, optimum frequency point needs scanning to determine, but also need to design good scanning algorithm, otherwise also may cause losing lock, add that the frequency of operation of single-chip microcomputer own is low, cannot parallel processing, so once complete measurement result needs long time, can not be applicable to the measurement occasion of high-speed mobile, measuring accuracy is poor, can not fast automatic tracking, belong to unreliable, the implementation of poor performance.
Summary of the invention
The object of the invention is to provide a kind of figure tracking formula helium light pump magnetic apparatus, it is characterized in that, described magnetometer is the exploration system based on programmable logic device (PLD) (PLD), the effect utilizing the basic logic unit in PLD to realize measure loop to reach identical with pure mimic channel, and be integrated in monolithic PLD logic chip.
Compared with existing two kinds of up-to-date helium light pump magnetic apparatus, its innovative point is, have employed the signal discrete that detector exports by superfast ADC (analog to digital converter), and Closed loop track analog hardware circuit huge for traditional complexity has been integrated in the middle of a single programmable logic device, realize the software implementation of hardware circuit.The measure loop of pure analog tracking helium optical pumping mainly contains the analog circuit units such as phase-sensitive detector (PSD), voltage controlled oscillator, integrator.Because the unit scale of programmable logic device (PLD) can reach ten million gate leve, and multidiameter delay computing can be supported, the phase-sensitive detector (PSD), voltage controlled oscillator, integrator etc. of analog circuit unit can be realized completely with numeric door unit, and effect is better, resolution is higher, therefore the effect such as measuring accuracy, locking time that analog hardware circuit is equivalent can be reached, simultaneously again due to employing is that digital programmable realizes, therefore there is not mimic channel temperature drift, debugging is complicated, production cost is high, bulky shortcoming.
Beneficial effect of the present invention: figure tracking formula helium light pump magnetic apparatus of the present invention is by popping one's head in, and high-speed ADC is changed, programmable logic device (PLD) (PLD), DAC, MCU, keyboard detection, and liquid crystal display is formed, and carries out high-acruracy survey to magnetic field.The all functions of the complicated hardware circuit of tradition (simulation phase-sensitive detector (PSD), FIFO, multiplier, totalizer, voltage controlled oscillator) are achieved owing to have employed monolithic PLD chip, the phase locked track precision not only possessing analog hardware circuit realiration is high, the advantage that real-time is good, the antijamming capability simultaneously also having possessed digital programmable is strong, be easy to debugging, not temperature influence, cost is low, low in energy consumption, volume is little advantage.
Tracking accuracy is high: owing to adopting the analog to digital converter of high-speed, high precision, and fpga chip is operated in higher frequency, and the mathematical operation computing length in theory of FPGA inside is unrestricted, and the longer signal that can differentiate of the length of computing is less, and therefore precision is higher.
Real-time is good: its inversion frequency of the high-speed AD converter of employing is up to 100MHz, and the clock frequency of FPGA is also 100MHz, therefore its response time is in 10 nanoseconds, and FPGA inside is all parallel computation, there is not the delay that serial computing is brought, therefore the response time just strictly equaled for 10 nanoseconds; Antijamming capability is strong: traditional magnetometer core component is all analog device, and analog device is all the impact being especially easily subject to the extraneous factors such as temperature as everyone knows, is easily disturbed by the various disturbing factors in the external world thus causes instrument unstable.And the present invention's employing is that pure digi-tal algorithm is to realize the core simulation circuit of conventional magnetic instrument, therefore the stability of algorithm and the temperature of environment, pressure, and various Radio frequency interference (RFI) all it doesn't matter, its secure threshold exempting to disturb is more much higher than the threshold value of mimic channel, therefore its antijamming capability is strong.
Accompanying drawing explanation
Fig. 1 is the heavy tracking helium optically pumped magnetometer structure of prior art and measuring principle figure, wherein 11-probe, 12-selective frequency amplifier circuit, 13-phase-sensitive detection circuit, 14-phase shifter, 15-modulation signal generator, 16-voltage controlled oscillator, 17-frequency multiplier circuit, 18-frequency counter, 19-integrating circuit, 110-high frequency excitation oscillator;
Fig. 2 is based on monolithic processor controlled optically pumped magnetometer the general frame, wherein 21-probe sensor, and 22-signal transacting AD samples, 23-single-chip microprocessor MCU, and 24-DDS, 25-power promotes;
Fig. 3 is figure tracking formula helium light pump magnetic apparatus schematic diagram of the present invention, wherein 31-probe sensor, and 32-signal transacting ADC gathers, 33-FIFO, 34-digital phase-sensitive detector, 35-digital integrator, 36-measure loop, 37-liquid crystal display, 38-MCU controls, 39-Keyboard Control, 40-modulation signal, 41-digital vco, 42-PLD, 43-DAC changes, 44-power amplification;
Fig. 4 is fifo structure figure in the PLD of magnetometer of the present invention, wherein 411-writing address generator, 412-dual port RAM, 413-reading address generator, the full signal generator of 414-sky;
Fig. 5 is digital phase sensitivity detection and the digital integrating circuit figure of magnetometer of the present invention, wherein 51-digital switch detection, and 52-is cumulative to be averaging, and N is sampling number;
Fig. 6 is the DDS ultimate principle figure of magnetometer of the present invention, wherein 61-totalizer, 62-phase register, 63-sine and cosine look-up table, 64-clock source, 65-frequency control word, 66-DAC;
Fig. 7 is the digital vco schematic diagram of magnetometer of the present invention, and wherein 71-modulation signal exports, and 72-integrator exports, and the sinusoidal digital signal of 73-exports.
Embodiment
The present invention is further described according to following embodiment and accompanying drawing, and those skilled in the art can understand, following embodiment and accompanying drawing only play the effect of explanation to the present invention.Without departing from the premise in the spirit of the present invention, any improvement the present invention done and substituting all within the scope of protection of the invention.
Tracking helium optically pumped magnetometer is divided into probe segment and host machine part.Optical system in probe mainly contains the parts such as helium lamp, absorption chamber, two lens, polaroid, λ/4 wavelength sheet, light activated elements composition.
First helium light pump magnetic apparatus is placed in tested external magnetic field, and make the axis of probe and outer magnetic field direction almost parallel; The monochromatic light (D1 line plays a major role) being excited helium lamp to make it to send 1083nm by the high frequency excitation oscillator in circuit, excites the helium in helium absorption chamber to make helium atom be in metastable state simultaneously; This light being helium lamp sends becomes directional light after lens I, then after polaroid, become the polarized light of 1083nm, and after the wavelength sheet of λ/4, become again circularly polarized light (is be make from metastable state 2 by the object of circularly polarized light
3excited state 2 is energized in S1
3atom in P1 must meet selection rule Δ Mf=± 1, left circularly polarized light meets and Δ Mf=+1, and right-circularly polarized light is satisfied with Δ Mf=-1), this circularly polarized light is directed on the metastable state orthohelium in absorption chamber, Zeeman splitting is produced, Zeeman level 2 under the effect of orthohelium outside magnetic field
3s1 state Atomic absorption D1 line transits to 2
3p1 state, the result of optical action makes atomic magnetic moment orientation and 2
3on a certain magneton sublevel of S1 state; Then the radio-frequency (RF) energy be supplied to by radio-frequency coil by radio frequency (RF) oscillator, upsets in metastable state the orientation responding atomic magnetic moment on magneton sublevel, thus produces magnetic resonance effect.As mentioned above, when being in metastable state 2
3atom in S1 is excited to 2
3p1 is because D1 line is by Atomic absorption, so now just weak by the light of absorption chamber; Through after a period of time, atom all focuses on after on a certain magneton sublevel, and just do not have atom to absorb D1 line again, the light so through absorption chamber is then the strongest.Visible, the intensity through absorption chamber light is the function of atomic orientation, and namely optical action makes atomic orientation effect strengthen, thus makes the light intensity grow through absorption chamber; Magnetic resonance effect makes atom go orientation effect to strengthen, thus the light intensity through absorption chamber is died down.
As can be seen here, when the most weak through the light of absorption chamber time, when namely there is magnetic resonance, the frequency of radio-frequency field equals the Zeeman transition frequency between two adjacent magneton sublevels, like this by the frequency of radio-frequency field during measurement magnetic resonance, the size of tested magnetic field T can be obtained.Its relation is as shown in the formula T (nT)=0.0356843F (Hz).
By above analysis, when surveyed changes of magnetic field, the light that the frequency how changing radio-frequency field rapidly makes it to maintain all the time through absorption chamber is the most weak, i.e. the change of the automatic frequency tracking external magnetic field of radio-frequency field, the required function realized of detection control circuit of Here it is tracking optical pumping magnetometer.
Fig. 3 shows figure tracking formula helium light pump magnetic apparatus structural drawing of the present invention, and as can be seen from Figure 3, magnetic exploration system of the present invention is primarily of probe segment and measure loop composition.The Digital Detecting loop that measure loop part comprises signal transacting, ADC gathers, utilize PLD basic logic unit to realize, DAC conversion, power amplification, its measuring principle and simulation tracing formula helium light pump magnetic apparatus similar, unlike the present invention by reprocessing after signal digital.The present invention uses the inner basic logic unit of PLD to realize digital hardware closed loop detect, by the measure loop digitizing of simulation tracing formula helium light pump magnetic apparatus, both the advantage that hardware closed-loop system high-speed is measured had been remained, also stability and the high precision of signal digital process is remained, combine all advantages of existing helium light pump magnetic apparatus, also there is circuit structure simple, greatly reduce the power consumption of system, the advantage such as volume and production cost.
Fig. 4 shows the structural drawing of FIFO in PLD, according to Fig. 4
A: First Input First Output (FIFO)
First Input First Output (FIFO) essence is a kind of memory circuit, and feature is the data first stored, and is first read out, and maintains the sequencing of data.In the present invention, FIFO gathers with ADC the buffering exported as the input of measure loop data.As can be seen from the figure, FIFO inside mainly contains dual port RAM, stores for data, and read/write address generator, and address code during for reading and writing data generates, also free full signal generator.The IP kernel that dual port RAM provides in using PLD to develop software realizes, and read/write address generator essence is one and adds 1 totalizer, when reading and writing enable, carry out WClk or RClk, totalizer adds 1, and accumulated result is delivered to dual port RAM read/write address bus, realizes the read-write operation of data.
Fig. 5 shows digital phase sensitivity detection and digital integrating circuit
B: digital phase sensitivity detection and digital integrating circuit:
Phase sensitive detection also can be called phase detector, and output quantity is proportional to the phase differential of two same input signals frequently.Conventional implementation has analog multiplier, and by signal multiplication post filtering, the DC voltage obtained is proportional to input signal phase difference, and advantage is speed, and circuit is simple, but the low poor stability of precision, can differentiate narrow range, is generally 0 ° to 90 °.The digital phase-sensitive detector of the present invention's design is made up of a two-way MUX21 and summation totalizer, averages to all data that detection exports.
Detection process: during CLK=1, DOA=A1=DIN, DOB=0, DO=DOA=DIN;
During CLK=0, DOA=0, DOB=B0=DIN, DO=-DOB=-DIN;
Detection result:
1, when input signal to differ 90 ° with clk, integration exports=0;
2, when input signal to differ 180 ° with clk, integration exports and equals negative maximum.
3, when input signal to differ 0 ° with clk, integration exports and equals positive maximum.
Fig. 6 shows the ultimate principle figure of DDS in the present invention.
C: modulation signal generator
The effect of modulation signal generator produces sinusoidal digital modulation signals, and with its digital square-wave with homophase frequently, for digital detection, use DDS to realize herein.As shown above, DDS is by totalizer, and phase register, sine and cosine look-up table, clock source forms.Totalizer adds up according to frequency control word, accumulated value is deposited phase register, as the Input Address of sine and cosine look-up table.Sine lookup table effect realizes the conversion of phase place to amplitude, and the amplitude information obtained is converted to analog signal output through DAC.Clock source provides timing reference for whole system work.
Fig. 7 shows digital vco of the present invention
D: digital vco:
The object of digital vco exports wobble frequency signal, incentive probe after DAC conversion.Its core is also direct digital synthesis technique (DDS), frequency by integrator export add the sinusoidal digital output of modulation signal and control, centre frequency is determined by integrator, therefore the sinusoidal digital quantity that modulation signal exports should be as shown in FIG. less, modulation signal is exported that sum-product intergrator exports and as the frequency control word of DDS, the output of voltage controlled oscillator is wobble frequency signal, and centre frequency is determined by the output of digital integrator.In real work, only when tenacious tracking, the centre frequency of voltage controlled oscillator output signal need be measured, accurately can calculate the value in magnetic field according to aforementioned formula.
Claims (1)
1. a helium light pump magnetic apparatus, is characterized in that comprising probe sensor (31), high-speed ADC converter (32), Programmable logic design (42), DAC (43), MCU (38), keyboard detection (39), liquid crystal display (37);
Described PLD comprises memory circuit FIFO (33), and this memory circuit FIFO gathers with ADC the buffering exported as the input of measure loop data;
The inner basic logic unit of described PLD realizes digital hardware closed loop detect, by the measure loop digitizing of simulation tracing formula helium light pump magnetic apparatus;
Described helium light pump magnetic apparatus also comprises modulation signal generator, described modulation signal generator by totalizer, phase register, sine and cosine look-up table, clock source form;
Described PLD achieves hardware circuit: all functions of digital phase-sensitive detector (34), FIFO (33), multiplier, totalizer and digital vco (41); Described digital vco in order to export wobble frequency signal, through DAC conversion after incentive probe; Also direct digital synthesis technique, frequency by integrator export add the sinusoidal digital output of modulation signal and control, determine centre frequency by integrator; Described digital phase-sensitive detector is made up of a two-way MUX2_1 and summation totalizer, averages to all data that detection exports;
Described FIFO (33) comprises the dual port RAM (412) stored for data, the read/write address generator (413) that during for reading and writing data, address code generates, and the full signal generator (414) of sky;
The inversion frequency of described high-speed ADC converter is 100MHz.
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| CN104198967B (en) * | 2014-09-28 | 2017-02-01 | 上海通用卫星导航有限公司 | Compact light component device for cesium optical pumping magnetometer |
| CN104316969B (en) * | 2014-10-11 | 2017-01-25 | 中国船舶重工集团公司第七一五研究所 | Intelligent digital helium optically-pumped magnetometer |
| CN109470398B (en) * | 2018-09-17 | 2021-01-05 | 西北工业大学 | Floating conditioning and collecting unit of fluid wall shear stress tester |
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| US6588701B2 (en) * | 2000-09-26 | 2003-07-08 | Rafael Armament Development Authority, Ltd. | Unmanned mobile device |
| CN102156303A (en) * | 2011-03-23 | 2011-08-17 | 中国船舶重工集团公司第七一五研究所 | Miniature helium optical pump magnetometer applicable to small-sized aircraft |
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| US6588701B2 (en) * | 2000-09-26 | 2003-07-08 | Rafael Armament Development Authority, Ltd. | Unmanned mobile device |
| CN102156303A (en) * | 2011-03-23 | 2011-08-17 | 中国船舶重工集团公司第七一五研究所 | Miniature helium optical pump magnetometer applicable to small-sized aircraft |
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