CN106383364A - Pseudo-random frequency-sweeping nuclear magnetic resonance detection instrument - Google Patents
Pseudo-random frequency-sweeping nuclear magnetic resonance detection instrument Download PDFInfo
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Abstract
The invention discloses a pseudo-random frequency-sweeping nuclear magnetic resonance detection instrument. The instrument comprises a control and communication module, a pulse transmitting module, a response signal receiving module, a frequency sweeping control module and a pulse frequency modulation module, wherein the response signal receiving module acquires nuclear magnetic resonance response signals excited by pseudo-random frequency-sweeping nuclear magnetic resonance excitation pulses and transits the nuclear magnetic resonance response signals to the control and communication module; and the control and communication module calculates the frequency deviation degree between the current excitation frequency and the actual Larmor frequency according to the features of the nuclear magnetic resonance response signals so as to judge whether the received response signals are the optimal response signals or not. The instrument disclosed by the invention can transmit pseudo-random frequency-sweeping nuclear magnetic resonance excitation pulses so as to excite nuclear magnetic resonance responses on multiple frequency points.
Description
Technical field
The invention belongs to geophysical exploration field, it is related to a kind of tunnel gushing water that can be used for and dashes forward mud advanced prediction and underground water detecting
Pseudorandom frequency sweep nuclear magnetic resonance, NMR detection instrument.
Background technology
It is a kind of geophysics that can verify the aqueous body position in underground and porosity and directly estimate its water yield that nuclear magnetic resonance, NMR detects
New method.Its principle is to be swashed using the artificial radio frequency exciting field that frequency is equal to Larmor frequency under magnetic field of the earth for the Hydrogen Proton in water
The free damping signal producing after sending out directly carries out quantitative judge to underground water content.At present, ground nuclear magnetic resonance, boring core
Magnetic resonance and laboratory nuclear magnetic resonance, NMR have been widely used in underground water detecting, landslide detection, oil well logging and rock sample
Many geophysics fields such as detection.Due to nuclear magnetic resonance, NMR have can direct look for water, in tunnel unfavorable geology and prominent
There are significant method advantage and important development meaning in the research of the prominent mud advanced prediction of water and application.
In probe procedure in field work and hole, Larmor frequency is simultaneously obtained in the magnetic field of the earth that accurately measurement is surveyed in area, then uses instrument
Tranmitting frequency nuclear magnetic resonance, NMR excitation pulse equal therewith is the key obtaining reliable NMR response signal.Due to magnetic field of the earth
Change over and skewness, front geological body there may be the factors such as magnetic anomaly and instrumental error；The frequency of excitation pulse
Often deviate real Larmor frequency.The amplitude of consequent NMR response signal will greatly reduce so that being submerged in
Cause among environment electromagnetic noise to observe the phenomenon of NMR response signal.At present, nuclear magnetic resonance apparatus design with
In the problem of research and development, generally research emphasis are placed on the aspects such as signal condition, noise suppressed and antenna optimization.And to how keeping away
Exempt from stimulating frequency and deviate true Larmor frequency aspect, lack enough research, there is no effective solution.
Specifically, there is a following difficult problem and deficiency in the design of nuclear magnetic resonance, NMR detection instrument and research and development：
(1) when carrying out in tunnel detecting in hole, if front of tunnel heading country rock is the high magnetic rocks such as mafic, Ultrabasic or metamorphic rock
Ferromagnetic mineral is contained, the size of front of tunnel heading magnetic field of the earth magnetic induction and inclination angle are due to above-mentioned magnetic in body and country rock
Abnormal generation is distorted, and the stimulating frequency Larmor frequency of nuclear magnetic resonance, NMR does corresponding change therewith.Due to front magnetic field of the earth
Unknown parameters, now calculate stimulating frequency and the true Larmor in front using the magnetic field of the earth of Tunnel interior measurement after face
There is deviation it is impossible to reliably excite the NMR response in the disaster water body of front in frequency.
(2) nuclear magnetic resonance, NMR excitation pulse adopts single frequency sinusoidal pulse, and primary emission is only capable of carrying out nuclear magnetic resonance, NMR to a frequency exciting.
Stimulating frequency and Larmor frequency exist to be needed during deviation constantly to convert stimulating frequency and can not estimate the number of stimulating frequency after conversion
Value.
(3) generation of single frequency sinusoidal pulse need to be using RLC resonance circuit and high-voltage capacitance charge-discharge modules.The frequency of excitation pulse
Control and need to be allowed to match thus reaching resonance with the induction reactance of coil and circuit by adjusting the capacitive reactance of external capacitor.Frequency-selecting is joined humorous
The realization of process is combined and through, by the connection in series-parallel that humorous electric capacity is joined in the multiple switching of relay, the quality that testing circuit feeds back current circuit
Factor is exported with pulse.Therefore to join humorous process quite time-consuming for frequency-selecting.And due to the key component of resonance circuit be join humorous
Inductance and electric capacity, therefore transmitter need the huge and heavy capacitive of circumscribed volume (to join humorous inductance typically by transmitting coil
Induction reactance provides).
Content of the invention
In order to solve the shortcoming of prior art, the present invention provides a kind of pseudorandom frequency sweep nuclear magnetic resonance, NMR detection instrument.The puppet of the present invention
Random frequency sweep nuclear magnetic resonance, NMR detection instrument can be used for the prominent mud advanced prediction of tunnel gushing water and underground water detecting, and can once see
In survey, multiple frequencies are carried out with nuclear magnetic resonance, NMR excite and pass through to adjust excitation pulse and frequency scan to obtain optimal response.
For achieving the above object, the present invention employs the following technical solutions：
A kind of pseudorandom frequency sweep nuclear magnetic resonance, NMR detection instrument, including control and communication module, the magnetic field of the earth in its collection measurement zone
Parameter simultaneously calculates the frequency modulation(PFM) function of for the first time pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse of transmitting, and by frequency modulation(PFM) function
It is sent to pulse frequency modulated module；
Pulse frequency modulated module, it produces frequency modulated signal according to the frequency modulation(PFM) function receiving and is sent to impulse ejection module；
Impulse ejection module, it is generated and transmitted by one group of pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse according to frequency modulated signal,
Carry out nuclear magnetic resonance, NMR to multiple frequencies to excite；
Response signal receiver module, the NMR response signal that its collection pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse is excited,
And it is sent to communication module；Described control is additionally operable to currently excite frequency according to the calculating of NMR response signal characteristic with communication module
With the frequency departure degree of true Larmor frequency, rate to judge whether the response signal receiving is optimal response signal：
If optimal response signal is it is determined that optimum excitating frequency record optimal response；
Otherwise, frequency departure degree is sent to frequency scanning control module, described frequency scanning control module is according to frequency departure
Degree carries out calculating frequency scanning direction and step-length carrys out regulating frequency modulation function signal, and inputs to pulse frequency modulated module；
Pulse frequency modulated module controls described impulse ejection module so that it is generated and transmitted by according to the frequency modulation(PFM) function signal receiving
The pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse of another group of different frequency, determines optimum excitating frequency.
Described pulse frequency modulated module, the frequency modulated signal that it produces is used for directly controlling the IGBT in impulse ejection module
The conducting of each brachium pontis of bridge circuit and shutoff, realized to pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse frequency and pulse duration
Control.
Described response signal receiver module using Ditital multichannel frequency-selecting reception by the way of, by set in advance multiple difference centers
The signalling channel of frequency gathers the NMR response signal that pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse is excited.
Described frequency scanning control module has automatically scanning and two kinds of working methods of manual scanning.
Described frequency scanning control module under automatically scanning mode, automatically sentence by the NMR response signal according to being currently received
The direction of fixed frequency scanning regulating frequency modulation function.
Described frequency scanning control module, under manual scanning mode, is adjusted with scanning step by host computer incoming frequency scanning direction
Section frequency modulation(PFM) function.
Described frequency scanning control module is passed through continuous to change frequency modulation(PFM) function so that pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse
Spectral characteristic slided along frequency axiss with fixing form, realize a series of NMR response on frequencies is scanned swashing
Send out.
Described impulse ejection module includes the bridge circuit being made up of switching tube and associated trigger circuit.
Described control is in communication with each other with host computer with communication module.
Beneficial effects of the present invention are：
(1) present invention is that in the detection of tunnel (and ground) nuclear magnetic resonance, NMR, disaster water body (underground reservoir) can not reliably excite
Problem provide feasible scheme, thus preferably solve gushing water dashing forward the quantitative judge at mud disaster water source and forecasting problem；In arteries and veins
Rush transmitting aspect, abandon using sinusoidal wave pulse then using the pseudorandom being made up of the bipolarity cycle square wave of multigroup different frequency
Frequency sweep nuclear magnetic resonance, NMR excitation pulse；Pulse is no longer necessary to RLC resonance circuit.Therefore, impulse ejection module is not needing
External huge and heavy join humorous electric capacity.Because bridge circuit can be integrated in solid state module, have small volume, lightweight,
Feature easy to control；Therefore using its as pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse radiating circuit be instrument achieves
Miniaturization and lighting.
(2) in terms of transmitting pulse frequency characteristic, the sequence circuit that instrument is consisted of integrated digital chip flexibly controls different frequencies
The cycle number of repetition of rate square wave is obtaining different spectral characteristic thus realizing exciting nuclear-magnetism on multiple frequencies in once observing altogether
Vibration response.
(3) on the mode of excitation of nuclear magnetic resonance, NMR, pulsatile once transmitting can be carried out to the NMR response on multiple frequencies
Excite.According to current NMR response feature, determine frequency scanning direction, change pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse
Frequency；Thus realizing in certain frequency band and NMR response are scanned exciting.
(4) in terms of NMR response signals collecting, received by Ditital multichannel frequency-selecting and achieve to pseudorandom frequency sweep nuclear-magnetism
The collection of the response signal on multiple frequencies that resonance excitation pulse excites.NMR response signal on different frequent points can be by
Gather respectively and record is for judging, thus finding out optimal NMR response signal.The mid frequency energy of signal receiving channel
Enough pass through program setting and adjust.This digital processing mode has high precision, strong antijamming capability and can pass through journey
Sequence controls a little.
(5) reliability in nuclear magnetic resonance, NMR excites aspect, this instrument realized " multi-frequency waves launch, frequency sweep excites, digital many
Road frequency-selecting receives " excite and acquisition method can effectively avoid detecting in hole with field work in due to looking for inaccurate Larmor's frequency
Off resonance response produced by rate.The optimal NMR response being obtained, is processed for follow-up data, inverting and explanation carry
Supply the observation signal of high-quality.
Brief description
Fig. 1 is the overall system structure of pseudorandom frequency sweep nuclear magnetic resonance apparatus.
Fig. 2 is impulse ejection and the frequency sweep control principle of pseudorandom frequency sweep nuclear magnetic resonance apparatus.
Fig. 3 is the operation principle of pseudorandom frequency sweep NMR response signal receiving module.
Fig. 4 is the contrast of nuclear magnetic resonance, NMR optimal response signal and off resonance response signal.
Fig. 5 is the workflow in the specific implementation process of pseudorandom frequency sweep nuclear magnetic resonance apparatus.
Specific embodiment
The present invention will be further described with embodiment below in conjunction with the accompanying drawings：
As shown in figure 1, the pseudorandom frequency sweep nuclear magnetic resonance, NMR detection instrument of the present invention includes impulse ejection module, pulse frequency modulated
Module, frequency scanning control module and control and communication module.Wherein, control and be in communication with each other with host computer with communication module.
Power module is pulse frequency modulated module, frequency scanning control module and control are powered respectively with communication module.
Power module realizes the transformation to external power supply, rectification and voltage stabilizing thus providing working power for the disparate modules of whole instrument.
Components and parts in overvoltage in power module, excessively stream and dump energy absorbing circuit guarantee instrument steady operation under rated condition,
By the collection essence that reliable electrical isolation ensures instrument work safety and signal is imposed to the loop of different electric pressures and module
Degree.For ensureing signals collecting precision and personal equipment safety, power module for whole instrument provide digitally, simulation ground and can
The ground protection leaned on.
Wherein, pseudorandom frequency sweep nuclear magnetic resonance, NMR detection instrument also includes transmitting and reception antenna (or probe), transmitting and reception antenna
(or probe) is the main peripheral hardware exciting and gathering NMR response signal.The profit when carrying out the field work of underground water detecting
Receive NMR response signal with receiving coil.Also can profit in addition to receiving coil when carrying out the prominent mud advanced prediction of gushing water in tunnel
It is acquired with the magnetic probe with bigger equivalent received area.
The number of turn of transmitting coil and the length of side are selected as needed.For the underground water detecting work carrying out in earth's surface, transmitting coil
The number of turn is 1～2 circle, 50m and 100m may be selected using coil length of side during square loop line according to investigation depth.For in hole
The gushing water prominent mud advanced prediction work carrying out, the number of turn of transmitting coil may be selected 4～8 circles according to investigation depth, and coil hangs over area
On face, girth is suitable with exploration face girth.Utilize receiving coil to receive nuclear-magnetism when carrying out the field work of underground water detecting
Resonance response signal.It is also with that there is bigger equivalent received in addition to receiving coil when carrying out the prominent mud advanced prediction of gushing water in tunnel
The magnetic probe of area is acquired.Carry out multipoint array-type using probe in face to observe to increase observation data volume, for follow-up
Inverting and data interpretation provide and more observe data.The scale of array observation is according to the length of side of face size and excitation variable winding
Determine.
Host computer achieves the instrument manipulation of interfacial type, instrument self checking, signals collecting data record by upper computer software.Instrument
The working condition of device, sampling NMR response signal and measurement when daily record of work can record in the form of a file and
Storage.
Described master system is made up of an industry control notebook and pc control procedure.Master system passes through upper computer software
Achieve the instrument manipulation of interfacial type, instrument self checking, signals collecting data record.The self-detection result of instrument, working condition,
Daily record of work when the NMR response signal of sampling and measurement can record in the form of a file and store.
(1) control and communication module
Control the entirety achieving each module of instrument with communication module to control, detect and the instruction with master system and data biography
Defeated.Additionally, the sensor in module can measure the magnetic field of the earth parameter in area, including earth's magnetic field magnetic induction, earth magnetism
Inclination angle and geomagnetic declination.
Control the pseudorandom frequency sweep core with communication module, the magnetic field of the earth parameter in measurement zone being gathered according to it and calculating transmitting for the first time
The frequency modulation(PFM) function signal of magnetic resonance excitation pulse, and frequency is adjusted to function signal is sent to pulse frequency modulated module.
Control and mainly have three functions with communication module：
The first is controlled to each module by embedded chip and detects；
Its two signal being responsible between instrument and host computer is transmitted with instruction.Control with communication module in and core be ARM core
Piece, is responsible for realizing the bottom control of instrument host.It is provided with analog sensor, Boolean value output sensor, electric current mutual in this module
Sensor etc. is used for working condition and the working environment of detecting instrument.Instrument host is passed through with data transfer with the instruction of host computer
RS-232 serial communication is realized.
Third, built-in magnetometer in this module is responsible for gathering magnetic induction, magnetic dip angle and the magnetic biasing surveying the magnetic field of the earth in area
Angle.Magnetic field data of Earth ARM chip according to being obtained calculates to be launched for the first time desired pseudorandom frequency sweep nuclear magnetic resonance, NMR and swashs
Send out the frequency modulation(PFM) function of pulse.Pulse frequency modulated module is adjusted to function according to frequency and controls impulse ejection module breaker in middle pipe to touch
Send out the transmitting realizing pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse with the generation of cut-off signals.
(2) impulse ejection module
Impulse ejection module, it is generated and transmitted by first group of puppet according to the frequency modulation(PFM) function signal controlling with communication module output
Random frequency sweep nuclear magnetic resonance, NMR excitation pulse.
In specific implementation process, the bridge-type electricity that impulse ejection module is consisted of high-power insulated gate bipolar IGCT (IGBT)
Road and associated trigger control circuit produce and pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse.Pseudorandom frequency sweep nuclear magnetic resonance, NMR excites arteries and veins
Punching is made up of the cycle square wave of different frequencies multiple within a period of time.The frequency of each square wave, cycle number of repetition and side
The number of ripple is controlled by pulse frequency modulated module.Voltage stabilizing in impulse ejection module ensures stable voltage output with clamp circuit
With rapidly switching off of pulse.
Impulse ejection module is responsible for realizing the transmitting of pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse.As shown in Fig. 2 impulse ejection mould
The core of block is the bridge circuit and trigger control circuit that high-power insulated gate bipolar IGCT (IGBT) forms.Q1～Q4Four
Individual IGBT pipe is located on four brachium pontis of bridge circuit respectively, D1～D4It is fly-wheel diode, ZLRepresent the impedance of excitation variable winding.
When excitation pulse is positive, Q1With Q4Two IGBT pipe conductings；When excitation pulse for reverse when, Q2With Q3Two IGBT
Pipe turns on.In Q1With Q4Turn off (conducting) to Q2With Q3In the transit time of conducting (shutoff), sustained diode2With
D3(D1With D4) conducting (shutoff) will not abrupt transients for the electric current in oad freewheels proof load.D5And D6Two instead simultaneously
The clamp circuit of di- pole pipe composition automatically shuts down when load terminal voltage is less than its conduction voltage drop, and terminal voltage is clamped to zero；Protect
Demonstrate,prove rapidly switching off of pulsed emission current.During whole impulse ejection, the trigger of IGBT is derived from pulse frequency modulated
Module.For avoiding power supply short circuit, the triggers circuit in impulse ejection module is removed and is ensured that IGBT can reliably trigger and turn off,
Also assure that two pipes on the brachium pontis of the same side two will not simultaneously turn on.
(3) response signal receiver module
Response signal receiver module, the NMR response signal that its collection pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse is excited,
And it is sent to control and communication module；Described control currently excites frequency with communication module according to the calculating of NMR response signal characteristic
With the frequency departure degree of true Larmor frequency, rate to judge whether the response signal receiving is optimal response signal：
If optimal response signal is it is determined that optimum excitating frequency record optimal response；
Otherwise, frequency departure degree is sent to frequency scanning control module, described frequency scanning control module is according to frequency departure
Degree carries out calculating frequency scanning direction and step-length carrys out regulating frequency modulation function signal, and inputs to pulse frequency modulated module；
Pulse frequency modulated module controls described impulse ejection module so that it is generated and transmitted by according to the frequency modulation(PFM) function signal receiving
Another group of new pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse；The frequency spectrum of new pulse is different from the pulse frequency spectrum of last transmitting, energy
The frequency that enough covering last time transmitting is not covered with is it is thus possible to be scanned exciting；Afterwards, response signal receiver module, control
System and communication module, frequency scanning module, pulse frequency modulated module and impulse ejection module repeating above said collection, analysis
The process launched with scanning is until receiving optimal response signal；All signals collecting are all by controlling and communicating during this period
The master system that module uploads stores and records.
Wherein, response signal receiver module using Ditital multichannel frequency-selecting reception by the way of, by set in advance difference centers frequency
The NMR response signal that the signalling channel of rate realizes pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse is excited is acquired and remembers
Record.Because pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse contains abundant frequency component, the nuclear magnetic resonance, NMR of multiple frequencies can be rung
Should be excited.Therefore, the collection of NMR response signal should be with the frequency component of pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse
Corresponding, thus ensureing that all NMR responses being excited on frequency are all observed.During every time scanning excites according to
Frequency spectrum according to the pseudorandom frequency sweep excitation pulse launched sets the mid frequency of program control frequency-selective network.Finally, by man-machine interaction
Function judges optimal NMR response signal.
The core component of response signal receiver module is dsp chip.Institute's signalling channel set in advance has not by DSP
Digital filter (program) with mid frequency is realized.Receiving coil and the received response signal of probe are through over-sampling, front
Dsp chip is inputted after putting frequency-selective filtering and analog digital conversion.There is programme controlled digital filter to receiving in dsp chip
Signal is further processed.The frequency range being located according to NMR response signal, the passband of preamplifier is 1.2kHz
To 3.5kHz.
As shown in figure 3, the digital filter program in dsp chip adopts parallel processing manner, pre-set n signal leads to
Road.The passband non-overlapping copies of n signalling channel are it is ensured that there is not the phenomenon of mixing in filtered signal.Each signal leads to
The spectrum signature of the pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse according to current transmitting for the mid frequency in road sets it is ensured that currently being swashed
The NMR response signal on each frequency sent out is extracted.Locked by digital quadrature in each signalling channel and amplify
Filter chip select amplification and denoising Processing are carried out to the response signal being digitized into.Signal after final process passes through
Control and be uploaded to master system with communication module and store.Under the working method that automatically scanning excites, the center frequency of each passage
Rate is automatically set and is sent to dsp chip by frequency scanning control module.Under the mode of operation that manual scanning excites, each passage
Mid frequency inputted by host computer or by frequency scanning control module automatically set and be sent to dsp chip.
(4) frequency scan control module
Frequency scanning control module has automatically scanning and two kinds of working methods of manual scanning.Automatically scanning mode is according to being currently received
NMR response signal automatically judge frequency scan direction and regulating frequency modulation function, manual scanning mode pass through upper
Machine software incoming frequency scanning direction and scanning step regulating frequency modulation function.By the core being currently received under automatically scanning mode
Magnetic Resonance inputs to the ARM chip controlling with communication module after the process of response signal receiver module.With
When, ongoing frequency is adjusted to function and feeds back to ARM chip by Tx port.ARM chip will judge according to response signal feature
Whether received response is off resonance response the deviation journey qualitatively judging current stimulating frequency and true Larmor frequency
Degree.Judge the response signal that receives be whether optimal response signal according to NMR response signal initial amplitude with excite
Relation curve between pulse square.
Nuclear magnetic resonance, NMR optimal response signal and different degrees of off resonance response signal is illustrated in accompanying drawing 4.As shown in figure 4, with
Optimal response signal is compared, and the tracing pattern of off resonance response signal is distorted, and initial amplitude greatly reduces, and signal phase is sent out
Raw skew.Obtained judged result is inputted to frequency scanning control module by Rx port, and frequency scanning control module is through meter
Calculation processes and draws scanning direction and step-length, afterwards regulating frequency modulation function by WR port, control signal is inputed to pulse
Frequency modulation(PFM) module.Pulse frequency modulated module controls IGBT conducting and shutoff in impulse ejection module according to abovementioned steps.
Under manual scanning mode, operator according to host computer record and the NMR response signal that shows judge received by response be
The no departure degree responding for off resonance and qualitatively judging current stimulating frequency and true Larmor frequency.
Direction and scanning step that operator is scanned in host computer incoming frequency, this instruction is sent to by host computer by serial communication
The main frame of instrument.The control of instrument host and communication module receives frequency surface sweeping direction with step-length and by its by Rx port input to
Frequency scanning control module, control signal is simultaneously inputed to by frequency scanning control module regulating frequency modulation function by WR port
Pulse frequency modulated module.Afterwards, pulse frequency modulated module controls the IGBT in impulse ejection module to lead according to abovementioned steps
Lead to and turn off.
(5) pulse frequency modulated module
Pulse frequency modulated module directly controls each brachium pontis of IGBT bridge circuit in impulse ejection module according to frequency modulation(PFM) function
Conducting and shutoff, realize to pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse frequency, the pulse duration and control.Excite arteries and veins
The frequency modulation(PFM) of punching is realized by the sequence circuit that integrated digital chip is constituted.Exported in the range of certain pulse duration
Pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse contain the square wave of multiple different cycles, containing abundant frequency content.Frequency is adjusted
Function processed controls the building form of these square-wave pulses and the cycle number of repetition of each frequency square wave.Therefore, change frequency modulation(PFM)
Function can make output pulse have different frequency contents, and then satisfaction excites requirement to the nuclear magnetic resonance, NMR on different frequent points.
Specific practice is：In a square-wave cycle, when excitation pulse is positive, pulse frequency modulated module is to impulse ejection mould
Block sends trigger and makes Q1With Q4Conducting, meanwhile, negater circuit in impulse ejection module is to Q2With Q3Send cut-off letter
Number ensure its shutoff；When excitation pulse is reverse, pulse frequency modulated module sends pick-off signal to impulse ejection module and makes Q1
With Q4Turn off, meanwhile, negater circuit in impulse ejection module is to Q2With Q3Send trigger and ensure its conducting.Frequency is adjusted
The functional value of function processed is the period frequency of pulse-triggered (cut-off) signal, is also in pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse
The frequency of square wave.The time that the fixed value that takes frequency modulation(PFM) function is experienced is pseudorandom frequency sweep divided by currently corresponding functional value
The cycle number of repetition of square wave in nuclear magnetic resonance, NMR excitation pulse.Therefore pulse-triggered (cut-off) signal is in the control of frequency modulation(PFM) function
The frequency of square wave and cycle number of repetition in the pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse that the lower change instrument of system is launched.Again due to
The spectrum signature of pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse, that is, its contained frequency content is with its square wave frequency of composition
The change of rate and cycle number of repetition and change.Therefore, pulse frequency modulated module can be according to frequency modulation(PFM) function controller unit
The frequency content contained by pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse of output, thus realize on multiple frequencies in certain frequency band
NMR response excited.
In specific implementation process, the workflow of pseudorandom frequency sweep nuclear magnetic resonance, NMR detection instrument is as shown in Figure 4.With reference to figure
5 pairs its elaborate.
Before starting working, lay measuring coil and receiving transducer surveying in area.Open master system, host computer system,
Carry out power-on self-test after system boot.The result of instrument self checking is uploaded to host computer simultaneously by the control of instrument host and communication module
Upper computer software shows.When instrument has fault, self-inspection is not passed through, and carries out self-inspection after fixing a breakdown again.Instrument does not have event
Barrier then pass through and carry out next step operation by self-inspection.
The magnetic field of the earth parameter in area is surveyed in the control of master system order instrument host with communication module measurement, including earth's magnetic field magnetic
Induction, geomagnetic inclination and geomagnetic declination；Afterwards, generate the pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse of transmitting for the first time
Frequency modulation(PFM) function is simultaneously sent to pulse frequency modulated module.Afterwards, associated transmissions parameter is passed through by serial ports by upper computer software
Communication is sent to instrument host.
Emission parameter includes：The current intensity of excitation pulse, excitation pulse persistent period, pseudorandom frequency sweep nuclear magnetic resonance, NMR excite arteries and veins
The number of the frequency of punching and excitation pulse square and intensity.
Instrument host completes relevant configuration after the emission parameter being connected to host computer transmission and waits firing order.Firing order is passed through upper
Control and the communication module of instrument host is assigned and be sent to position machine.
Control and receive after firing order with communication module, pulse frequency modulated module gives birth to frequency modulated signal according to frequency modulation(PFM) function,
Control the generation of impulse ejection module breaker in middle pipe trigger.Transmitter module is according to the frequency being inputted by pulse frequency modulated module
Modulated signal, is generated and transmitted by first group of pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse.
After transmitting terminates for the first time, the IGBT used of impulse ejection module turns off rapidly in the presence of clamp circuit.Meanwhile,
Response signal receiver module receives and processes response signal.NMR response on each frequency connects through Ditital multichannel frequency-selecting
The n signalling channel received is filtered and amplifies, and the n after serial communication will be processed is individual with communication module for host computer control afterwards
Signal data in passage stores after being uploaded to host computer and is shown on screen.By launching a series of excitation pulse square, instrument
The process thinking highly of again above-mentioned transmitting with observation finally gives the initial amplitude that each excites frequency coker Magnetic Resonance and excites
Relation between pulse square.Excitation pulse square is the product with the pulse duration for the current intensity of excitation pulse.In same arteries and veins
Under the control of modulated function, after emission parameter is inputted by host computer, the pulse duration no longer changes.Instrument host controls
With the ARM chip in communication module, corresponding emission current intensity is calculated according to the intensitometer of excitation pulse square to be launched.Arteries and veins
Rush transmitter module and voltage is changed thus launching the electric current of different amplitudes according to the emission current intensity being calculated.
All pulse square transmittings and response signal gather after finishing.Upper computer software by signal initial amplitude in each passage and swashs
The relation sending out pulse square is depicted as curve respectively and is shown on screen.If some channel reception in n receiving channel arrives
Optimal response signal, then observation terminates.If none of channel reception is to optimal response signal, need to be scanned exciting.
Judge the response signal that receives be whether optimal response signal according to the initial amplitude of NMR response signal and excitation pulse
Relation curve between square.
As shown in figure 4, compared with optimal response signal, the initial amplitude of off resonance response signal greatly reduces, and signal phase is sent out
Raw change.Described in Fig. 4 change impulse modulation function after be scanned exciting mode have automatic with manual two kinds.Instrument is carried out
The process of frequency scanning as previously described, repeats no more here.Need specified otherwise, during scanning excites, ring
In induction signal receiver module, the mid frequency of n passage of digital filter and passband are inputted by host computer or automatically scanning work(
Can set.Ensure that excited NMR response can be received with this.The process that multiple scanning excites knows that a certain signal leads to
Optimal response signal is have received, observation just can terminate in road.All explanation signals in observation process all can be led to by serial ports
Letter is uploaded to host computer in real time and stores and be shown on screen.
Although the above-mentioned accompanying drawing that combines is described to the specific embodiment of the present invention, the not limit to the scope of the present invention
System, one of ordinary skill in the art should be understood that on the basis of technical scheme, and those skilled in the art do not need to pay
Go out the various modifications that creative work can make or deformation still within protection scope of the present invention.
Claims (9)
1. it is characterised in that including controlling and communication module, its collection measures a kind of pseudorandom frequency sweep nuclear magnetic resonance, NMR detection instrument
Magnetic field of the earth parameter in area simultaneously calculates the frequency modulation(PFM) function of the pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse of transmitting for the first time, and
Frequency modulation(PFM) function is sent to pulse frequency modulated module；
Pulse frequency modulated module, it produces frequency modulated signal according to the frequency modulation(PFM) function receiving and is sent to impulse ejection module；
Impulse ejection module, it is generated and transmitted by one group of pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse according to frequency modulated signal,
Carry out nuclear magnetic resonance, NMR to multiple frequencies to excite；
Response signal receiver module, the NMR response signal that its collection pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse is excited,
And it is sent to communication module；Described control is additionally operable to currently excite frequency according to the calculating of NMR response signal characteristic with communication module
With the frequency departure degree of true Larmor frequency, rate to judge whether the response signal receiving is optimal response signal：
If optimal response signal is it is determined that optimum excitating frequency record optimal response；
Otherwise, frequency departure degree is sent to frequency scanning control module, described frequency scanning control module is according to frequency departure
Degree carries out calculating frequency scanning direction and step-length carrys out regulating frequency modulation function signal, and inputs to pulse frequency modulated module；
Pulse frequency modulated module controls described impulse ejection module so that it is generated and transmitted by according to the frequency modulation(PFM) function signal receiving
The pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse of another group of different frequency, determines optimum excitating frequency.
2. as claimed in claim 1 a kind of pseudorandom frequency sweep nuclear magnetic resonance, NMR detection instrument it is characterised in that described pulse frequency
Modulation module, the frequency modulated signal that it produces is used for directly controlling each brachium pontis of IGBT bridge circuit in impulse ejection module
Conducting and shutoff, realize to pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse frequency and the control in pulse duration.
3. as claimed in claim 1 a kind of pseudorandom frequency sweep nuclear magnetic resonance, NMR detection instrument it is characterised in that described response signal
Receiver module, by the way of Ditital multichannel frequency-selecting reception, is adopted by the signalling channel of multiple different center frequency set in advance
The NMR response signal that collection pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse is excited.
4. as claimed in claim 1 a kind of pseudorandom frequency sweep nuclear magnetic resonance, NMR detection instrument it is characterised in that described frequency scanning
Control module has automatically scanning and two kinds of working methods of manual scanning.
5. as claimed in claim 4 a kind of pseudorandom frequency sweep nuclear magnetic resonance, NMR detection instrument it is characterised in that described frequency scanning
Control module, under automatically scanning mode, automatically judges the direction frequency scanning according to the NMR response signal being currently received
And regulating frequency modulation function.
6. as claimed in claim 4 a kind of pseudorandom frequency sweep nuclear magnetic resonance, NMR detection instrument it is characterised in that described frequency scanning
Control module under manual scanning mode, by host computer incoming frequency scanning direction and scanning step regulating frequency modulation function.
7. as claimed in claim 4 a kind of pseudorandom frequency sweep nuclear magnetic resonance, NMR detection instrument it is characterised in that described frequency scanning
Control module passes through the continuous frequency modulation(PFM) function that changes so that the spectral characteristic of pseudorandom frequency sweep nuclear magnetic resonance, NMR excitation pulse is with fixation
Form along frequency axiss slide, realize a series of NMR response on frequencies is scanned exciting.
8. as claimed in claim 1 a kind of pseudorandom frequency sweep nuclear magnetic resonance, NMR detection instrument it is characterised in that described impulse ejection
Module includes the bridge circuit being made up of switching tube and associated trigger circuit.
9. as claimed in claim 1 a kind of pseudorandom frequency sweep nuclear magnetic resonance, NMR detection instrument it is characterised in that described control with logical
Letter module is in communication with each other with host computer.
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| CN106199739A (en) * | 2016-07-05 | 2016-12-07 | 吉林大学 | A kind of nuclear magnetic resonance, NMR water detector discharger and detection method |
| CN106871993A (en) * | 2017-04-14 | 2017-06-20 | 西安翼飞软件科技有限公司 | External vertical section probing wave liquid level contains water finder |
| CN107782756A (en) * | 2017-09-27 | 2018-03-09 | 中国科学院电工研究所无锡分所 | The automatic search center frequency approach of nuclear magnetic resonance core analyzer |
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| CN109031433A (en) * | 2018-07-18 | 2018-12-18 | 卢氏县地质勘查研究所 | A kind of nuclear magnetic resonance remote-sensing detector |
| CN109031434A (en) * | 2018-07-18 | 2018-12-18 | 卢氏县地质勘查研究所 | A kind of frequency-sweeping apparatus of nuclear magnetic resonance remote-sensing detector |
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| CN114487954A (en) * | 2022-04-14 | 2022-05-13 | 中国科学院精密测量科学与技术创新研究院 | Multichannel receiving and transmitting NMR method for accurately measuring field intensity and distribution of electromagnet |
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| CN107782756A (en) * | 2017-09-27 | 2018-03-09 | 中国科学院电工研究所无锡分所 | The automatic search center frequency approach of nuclear magnetic resonance core analyzer |
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| CN109031433A (en) * | 2018-07-18 | 2018-12-18 | 卢氏县地质勘查研究所 | A kind of nuclear magnetic resonance remote-sensing detector |
| CN109031434A (en) * | 2018-07-18 | 2018-12-18 | 卢氏县地质勘查研究所 | A kind of frequency-sweeping apparatus of nuclear magnetic resonance remote-sensing detector |
| CN110989009A (en) * | 2019-11-27 | 2020-04-10 | 吉林大学 | High-sensitivity compensation type underground metal unexplosive object detection device and detection method |
| CN110989009B (en) * | 2019-11-27 | 2021-04-06 | 吉林大学 | High-sensitivity compensation type underground metal unexplosive object detection device and detection method |
| CN114487954A (en) * | 2022-04-14 | 2022-05-13 | 中国科学院精密测量科学与技术创新研究院 | Multichannel receiving and transmitting NMR method for accurately measuring field intensity and distribution of electromagnet |
| CN114487954B (en) * | 2022-04-14 | 2022-07-01 | 中国科学院精密测量科学与技术创新研究院 | Multichannel transmitting-receiving NMR method for accurately measuring field intensity and distribution of electromagnet |
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