CN102262096A - Frequency-mixing technology-based reflection type microwave water ratio measuring device - Google Patents
Frequency-mixing technology-based reflection type microwave water ratio measuring device Download PDFInfo
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Abstract
The invention belongs to the technical field of microwave application and particularly relates to a frequency-mixing technology-based reflection type microwave water ratio measuring device. The frequency-mixing technology-based reflection type microwave water ratio measuring device consists of a horn-shaped microwave receiving-transmitting waveguide arranged in a stainless steel cylinder, a microwave cavity oscillator, a preposed instrument amplifying circuit board fixed on the inner wall of a rear seat of the stainless steel cylinder and a water signal displaying control terminal. A direct current frequency-mixing voltage signal output by the microwave cavity oscillator is amplified by the preposed instrument amplifying circuit board and is transmitted to the water content signal displaying control terminal; and the direct current frequency-mixing voltage signal is subsequently processed in the circuit, thereby the water content of a material to be measured is displayed by a liquid display screen at the water content signal displaying control terminal. The frequency-mixing technology-based reflection type microwave water ratio measuring device disclosed by the invention can be used for carrying out high-precision non-destructive measurement on water content of materials such as grain moisture content, concrete humidity, tobacco water content, water content of textile chemical products, thus the application range is wide.
Description
Technical field
The invention belongs to technical field of microwave application, be specifically related to a kind of reflection type microwave moisture percentage measuring apparatus based on frequency mixing technique.
Technical background
In the industrial and agricultural production process, the water percentage of some material has very important influence to the performance quality and the production efficiency of product, and this is comprising processing and manufacturing industry such as grain, tobacco, paper, coal stone, soil, chemical fertilizer, weaving, concrete and oil.The material water ratio standard is generally used the wet basis method and is calculated, and promptly tries to achieve with the proportion of the difference of dry back weight before dry by measuring it.And measure for indirect method, mainly containing electric-resistivity method, capacitance method, NEUTRON METHOD, microwave method and infrared method etc. both at home and abroad, its characteristics, the scope of application, measuring accuracy etc. have nothing in common with each other.
In some occasion, require the water percentage of online nondestructive measurement material, and then realize entire production process is carried out line closed loop control, this just has higher requirement to humidity measuring method.The Microwave Measurement technology is a new technology that grows up on bases such as microwave electronics and Microwave Measurement Technique, because medium has physical characteristicss such as reflection, transmission, scattering, resonance and Doppler effect to microwave, can interact by the mode and the medium of space radiation, sensor can not contact with measured matter in the measuring process, is very suitable for online Non-Destructive Testing.
Microwave is the electromagnetic wave of very high frequency, and under microwave action, the water dipole frequently commutates and consumes a large amount of electric energy, and the characteristic of hydrous matter this polarization loss in microwave field can characterize by its composite dielectric constant in microwave field.Theory and experimental study show, when microwave passes through hydrous matter, the loss of the microwave energy that is caused by moisture is far longer than the loss that other dry causes, water cut in the material is with its specific inductive capacity of remarkable influence, therefore measure the physical quantitys relevant such as power attenuation by the microwave of material, phase change, resonance frequency with specific inductive capacity, just can record indirectly water cut in this material how much.
Microwave detection method can be divided into space wave method, Transmission line method resonant cavity method at present, and wherein back two kinds of methods are suitable for contact type measurement, unsuitable on-line measurement.For the space wave method, different according to microwave with the measured medium action mode, can divide transmission-type and reflective two kinds, its principle is by measuring microwave and measured medium transmission part or reflecting part amplitude, phase place size and variation thereof behind space behavior, reflecting the material water ratio size indirectly.
Reflection type microwave hygrometric device because its transceiver, is easy to install, and characteristics such as be not subjected to that material thickness influences are convenient to be applied on the online detection production line.At present both at home and abroad on reflection type microwave hygrometric sensor design, adopt emission with receive isolated, promptly between microwave source and the detection tube via microwave devices such as isolator, circulators with microwave source and reflection echo signal isolation, detect separately.Because this sonde configuration is complicated, easily introduces noise, the more high shortcoming of cost has limited its large-scale application.
Present Research based on domestic and international microwave moisture measurement, the present invention is applied to microwave transmitted wave and reflection wave frequency mixing technique in the hygrometric, adopt aluminium alloy wave-guide cavity wave oscillator, matching design is received and dispatched electromagnetic horn and signal processing circuit accordingly, develops a kind of novel reflection type microwave hygrometric device based on frequency mixing technique.Its structure is simple and clear, easy operating, and measuring accuracy height, scope are wide, and antijamming capability is strong, can realize online harmless continuous coverage, and cost is lower, and wide application prospect is arranged aspect industrial and agricultural production.
Summary of the invention
The purpose of this invention is to provide a kind of reflection type microwave moisture percentage measuring apparatus based on frequency mixing technique.This device is with the echoed signal mixing of microwave local oscillation signal and tested material reflection, mixed frequency signal is exported intermediate-freuqncy signal after microwave cavity oscillator internal circuit low-pass filtering, when the microwave local oscillation signal equates with the frequency of echoed signal when relative fixed (microwave transmitting and receiving waveguide 4 and tested material 1 position), resulting intermediate-freuqncy signal is the dc signal that comprises the tested material moisture information, again this direct current mixing voltage signal is carried out subsequent treatment on the circuit, thereby obtain the moisture of tested material.
Reflection type microwave based on frequency mixing technique of the present invention is surveyed the water percentage device, by be installed on horn-like microwave transmitting and receiving waveguide 4, the microwave cavity oscillator 6 in the stainless steel cylinder 3, preposition instrument magnification circuit plate 7, the moisture signal display control terminal 9 that is fixed on stainless steel cylinder 3 back seats 8 inwalls formed; Microwave transmitting and receiving waveguide 4 is installed on the inwall of stainless steel cylinder 3 by volution 5; Microwave cavity oscillator 6 is installed in the rear end of microwave transmitting and receiving waveguide 4 by screw, in order to producing the microwave local oscillation signal of corresponding survey frequency, and export the direct current mixing voltage signal that comprises the tested material moisture information with after the echoed signal of tested material 1 reflection and the microwave local oscillation signal mixing low-pass filtering; Front end at stainless steel cylinder 3 is equipped with potsherd 2, and potsherd 2 is close to tested material 1 to reach pinpoint accuracy; By the direct current mixing voltage signal of microwave cavity oscillator 6 output after preposition instrument amplifying circuit 7 amplifies, be sent to moisture signal display control terminal 9, again this direct current mixing voltage signal is carried out subsequent treatment on the circuit, thereby on the LCDs of moisture signal display control terminal 9, show the moisture of tested material.
The front console place of moisture signal display control terminal 9 is provided with LCDs, signal mode selection key, analog signal output interface, the direct current mixing voltage signal that preposition instrument amplifying circuit 7 amplifies is after the internal circuit of moisture signal display control terminal 9 is handled, by the numerical value of LCDs demonstration tested material 1 water percentage, voltage or the current analog signal relevant of analog signal output interface output simultaneously with tested material 1 water percentage.
The basic structure of apparatus of the present invention as shown in Figure 1, Fig. 1 (a) is apparatus of the present invention basic structure synoptic diagram, Fig. 1 (b) is the device appearance synoptic diagram; The 1st, tested material typically can be the not material of containing metal impurity such as the sandstone that contain water, grain, paper, cloth, the 2nd, and the round ceramic sheet.
Microwave transmitting and receiving waveguide 4 is used for launched microwave and receive reflection echo, emission angle and caliber size and microwave transmission frequency and with tested material apart from relevant.Volution and outer volution two parts were rubber or plastic material in volution 5 comprised, interior volution sticks with glue in the outside of microwave transmitting and receiving waveguide 4, and outer volution sticks with glue in the inwall of stainless steel casing 3, interior volution and the mutual interlock of outer volution.In the equipment debugging stage, according to the applied field of hygrometric device difference, volution in needing manually to rotate in advance, and then the distance of regulating 1 of microwave transmitting and receiving waveguide 4 and tested material, after definite microwave transmitting and receiving waveguide 4 reaches the position of optimum measurement sensitivity, with the fixing inside and outside volution of screw, make the stationkeeping of microwave transmitting and receiving waveguide 4.The optimum sensitivity method for determining position, relevant with the sensor output voltage signal waveform, will be specified in the microwave mixer principle later.
Concrete, the typical sizes parameter of hygrometric device of the present invention is as follows: stainless steel cylinder 3 wall thickness 3～7mm, external diameter 75～120mm, potsherd 2 thickness 4～10mm, diameter 70～110mm; By the rotation of volution 5, the front and back adjustable distance of microwave transmitting and receiving waveguide 4 is between 10～50mm; Volution 5 inside and outside volution phase interlocks, external diameter 70～110mm, volution adjustable length are 10～50mm, its design size and stainless steel cylinder diameter coupling.
Microwave transmitting and receiving waveguide 4 is made by alloy material or metal-coated membrane material, and the wide D1 of its front end is 40mm～50mm, and high D2 is 30mm～40mm, and length is between 40mm～50mm, and the size of rear end size and microwave cavity oscillator 6 is complementary; The wide L1 of microwave cavity oscillator 6 is 22.9mm, and high L2 is 10.2mm, and the frequency of the microwave intrinsic signals of generation is 10.525GHz, and power is 20mW, and the continuous-current excitation voltage of this microwave cavity oscillator is 8V.
The microwave cavity oscillator 6 that figure (c) is in the practical application to be adopted among Fig. 4, figure (d) is the schematic appearance of microwave transmitting and receiving waveguide 4.In order to make microwave equipment working stability low cost, the microwave cavity oscillator of selecting for use Zhejiang connection letter Electronics Equipment Co., Ltd to produce in the design, realize the emission of microwave local oscillation signal and the reception and the mixing output of echoed signal, parameter is the serial cavity mixing oscillator of 10GHz, 20mW.This oscillator adopts single-ended gallium arsenide negative resistance microwave device, realizes frequency stabilization, little, the DC low-voltage power supply of harmonic wave.Cooperation by body effect tube or snowslide pipe and wave guide resonance cavity becomes microwave radio power to the low-voltage direct Power Conversion.The frequency of the microwave that oscillator produces is regulated decision by oscillating diode, wave-guide cavity wave, adjusting screw.Output power and microwave device, wave-guide cavity wave Q value are relevant, and by selecting different cavitys and device, the microwave transmission frequency can be adjusted within the specific limits, realizes the condition of work of best hygrometric.
Among Fig. 4, the function of the each several part of microwave cavity oscillator 6 is as follows: the 10th, and microwave starting of oscillation and Frequency mixing processing microstrip circuit, be affixed on wave-guide cavity wave inwall place, effect is voltage bias and the matched impedance that operate as normal is provided for oscillating diode and mixer diode, and provides low-pass filtering for mixing output; The 11st, mixer diode runs through the port that is put in resonator cavity and can effectively receive echoed signal from microwave transmitting and receiving waveguide 4; The 12nd, microwave oscillation diode screw base, it is positioned at microwave cavity oscillator centre, and the microwave oscillation diode places intra resonant cavity; The 13rd, the frequency trim screw, concrete oscillation frequency is chosen relevant with length and width L1, the L2 of square wave guide cavity; The 14th, the input and output lead-in wire of DC voltage-stabilizing module and power supply and signal, because microwave device is a sensitive element, so the stability requirement to voltage is higher, the DC voltage of 8V and reference ground end are by (8V), the input of (GND) two lines, mixed frequency signal is by the output of (Si) line, and power lead and signal wire are connected to an end of preposition instrument magnification circuit plate 7.
The present invention is applied to the microwave mixer technology in the detection to material moisture humidity, and concrete mixing principle is described as follows:
Fig. 2 is local oscillation signal and echoed signal mixing schematic diagram (local oscillation signal is the microwave signal of microwave cavity oscillator emission, and echoed signal is promptly via the microwave of tested material surface reflection).U wherein
LThe expression local oscillation signal, oscillation frequency is ω
LU
SBe echoed signal, frequency is ω
SE
0For satisfying the direct current biasing that normal mixing Q value is applied; D1 is the Schottky mixer diode, in the circuit promptly is to utilize mixer diode D1 electric current and voltage nonlinear characteristic, realizes the mixing output to local oscillation signal and echoed signal; Z
S, Z
L0Be respectively microwave local oscillation, the echoed signal equiva lent impedance in circuit; Z
LBe circuit load, its both end voltage U
OBe the mixing output voltage.
Local oscillation signal and echoed signal are expressed as respectively:
U
L(t)＝U
Lcosω
Lt (1)
Echoed signal that receives in the actual measurement and local oscillation signal are in a ratio of a small voltage increment, can further embody the mixed frequency signal frequecy characteristic with the loop signal electric current in each working point expansion in Taylor series:
First is the large-signal that flows through diode under the local oscillator excitation in the expansion, comprises DC terms, local oscillation signal first-harmonic and harmonic term thereof.Other are as echoed signal U in the formula
SHour be the small-signal composition, can only get second, at this moment:
G in the formula
nBe the Fourier expansion item that the mixer diode electricity is led g (t), the mixer diode electricity is led and is defined as
So after local oscillator and Dc bias size was determined, the electricity of mixer diode was led and is fixed value.
Fig. 3 is by (4) formula analysis each frequency spectrum analysis chart that draws, and the line segment height is promptly represented this frequency signal size relative value.(4) in the formula during for n=1, the frequency item is ω
L-ω
S, i.e. ω in the spectrogram
0Item (ω
0=ω
L-ω
S), do following analysis, thus and the loop current that produces is:
During actual measurement, microwave probe keeps relative static with tested material, does not produce Doppler effect, local oscillation signal frequencies omega this moment
LWith the echoed signal frequencies omega
SEquate, (5) but the formula abbreviation is following form:
This formula explanation is when the local oscillation signal frequencies omega
LWith the echoed signal frequencies omega
SWhen equating, intermediate frequency item I
0Become direct current, the mixing electricity is led g in the formula
1Be constant, U
SBe the reflection echo amplitude, material water percentage and the positive correlation of microwave reflection echo amplitude, φ is a reflection echo phase place relative value, its size is the periodic function of microwave probe and material reflecting interface distance, whenever mobile half wavelength distance, the φ value changes one-period.
In the actual hygrometric process of explanation of more than deriving, can be with mixed frequency signal by after the low-pass filtering, output has been converted to the intermediate-freuqncy signal of direct current.Simultaneously in order to make probe be in best effort sensitivity position, should regulate distance between microwave probe and the microwave reflection face, measure the microwave cavity oscillator (amplitude of voltage signal (Si) line of 6 outputs with voltage table simultaneously, during maximum value, probe promptly is in the optimum sensitivity position in amplitude reaches one-period.The different amplitudes of output direct current signal promptly reflect the size of the corresponding water percentage of material.
7 is preposition instrument amplifier circuit parts among Fig. 1, and this part is positioned over stainless steel cylinder inside, and effect is that the direct current mixing voltage signal to microwave cavity oscillator 6 output returns to zero and amplifies.About 200～500mV, behind prime amplifier, the variation range of this voltage signal is modulated in 0～5V scope by the dynamic change scope of the direct current mixing voltage signal of microwave cavity oscillator 6 output.Require prime amplifier highly sensitive when selecting chip for use, it is strong to suppress the common-mode noise ability, and possesses adjusting at zero point and sensitivity adjusting function, and some Common Instrument amplifiers are available, as AD620, the AD627 etc. of ADI.In the equipment debugging stage, use the field difference of hygrometric degree according to device, after definite good microwave transmitting and receiving waveguide 4 reaches the position of optimum measurement sensitivity, need return to zero and the enlargement factor adjusting to this preposition instrument amplifying circuit 7, signal is modulated in the effective output area of 0～5V.The specific design scheme of this partial circuit describes in detail in an embodiment.
Figure 10 is that microwave surveys moisture signal processing flow synoptic diagram, has reflected the signal processing model of unit such as reception, microwave mixer, low-pass filtering output and zeroing amplification of emission, the echoed signal of microwave.
Among Figure 10 (e), launched microwave and reception echo are represented microwave of being launched by microwave transmitting and receiving waveguide 4 and the echoed signal that receives respectively, and microwave frequency is all 10.5GHz, receive the amplitude of the amplitude of echo much smaller than the emission echo; After mixer diode 11 mixing in microwave cavity oscillator 6, the main frequency spectrum of mixed frequency signal is shown in (f) among the figure, because the frequency of two signals of participation mixing is identical, so in frequency spectrum (f), required intermediate-freuqncy signal is that frequency is the direct current signal of 0Hz, and 10.5GHz and 21GHz item are original signal frequency and frequency-doubled signal frequency in the frequency spectrum; After microwave cavity oscillator 6 inner low-pass filtering, high-frequency signal in the mixing frequency spectrum (f) is filtered, (g) expression is that 0%～15% sand is when testing to water percentage among the figure, the Si end output schematic graph of microwave cavity oscillator 6, in water percentage was 0%～15% scope, the variation of output signals scope was in 1V; After modulation is amplified in preposition instrument amplifying circuit 7 zeroings, the output mode of signal is shown in figure (h), and when changing in the scope of tested sand water percentage 0%～15%, preposition instrument amplifying circuit 7 output signals are crossed 0 point, maximal value is 5V, and between 0～5V monotone variation.
After preposition instrument amplifying circuit 7 modulation, the voltage signal of amplification is drawn by base 8 centers through lead, delivers to the moisture signal display control terminal 9 of front end; The lead of being drawn by base 8 centers comprises ± 15V power lead, 8V power lead, GND line, and S
OutSignal wire; Moisture signal display control terminal 9 is mainly realized the controls of signal samplings and output mode, and the concrete water cut of material is intuitively shown with the numerical value form, and the simulated data output port is provided simultaneously.
The Appearance Panel of moisture signal display control terminal 9 is shown in (b) among Fig. 1, and the upper left side of panel is provided with the LCD1602 LCDs, shows material water ratio numerical value; The below of display screen is provided with Sig and two binding posts of GND, and the simulation output of water percentage signal is provided; The upper right side of panel is provided with " in real time ", " average " model selection control button 20, is used for controlling the sampling processing pattern of internal circuit, and when respective keys was pressed, internal circuit can drive the LED lamp that is positioned at the button top, makes it to light; The bottom righthand side of panel is provided with " 4～20mA ", " 0～5V ", " 0～10V " model selection control button 20, is used for controlling the output mode of water percentage signal, and each button top has the LED lamp to indicate the output mode of current device equally.
Particularly, signal sampling designs following dual mode: (1) is for satisfying the Monitoring and Controlling requirement in the commercial production control, and the signal real-time sampling output mode of design, the humidity of materials voltage signal is cycle detection output with 0.3s, when " in real time " button in the panel was pressed, this pattern started; (2) for satisfying the signal average output mode that the on-line continuous measurement requirement designs in the industrial and agricultural production, side circuit is realized the moisture signal of continuous coverage is carried out the average processing, and with 10s by one-period export in this section Measuring Time the medial humidity of survey material, this pattern is started by key control by " average " in the panel.
On the signal output mode is selected, for the different water cut rate that the makes material form by curtage characterizes, circuit designs 4～20mA, 0～5V, three kinds of different curtage output modes of 0～10V respectively, measures the needs of middle and long distance transmission and the monitoring of central control room closed loop to satisfy industrial and agricultural production; Simulating signal provides interface by moisture signal display control terminal 9 Sig of front console place and two binding post outputs of GND for follow-up engineering technical personnel carry out the processing of moisture signal data.
Particularly, Fig. 5 is a signal processing circuit functions of modules block diagram in the moisture signal display control terminal 9.Signal input moisture signal display control terminal 9 selects circuit 23 to form by supply module 15, relay 16, signal average circuit 17, AD converter 18, single-chip microcomputer 19, model selection control button 20, liquid crystal display 21, DA converter 22, output mode.After preposition instrument amplifier 7 zeroings were amplified, it was the voltage signal that 0～5V changes that moisture signal is modulated to amplitude by the direct current mixing voltage signal of microwave cavity oscillator 6 output; Behind the signal input moisture signal display control terminal 9, at first judge through relay 16, this relay is by single-chip microcomputer 19 controls, single-chip microcomputer is controlled this relay and is connected a1 end (associative mode selects the control button to select " in real time " pattern) or a2 end (associative mode selects the control button to select " average " pattern) according to the difference input of model selection control button 20; Voltage signal through a1 end is directly sent into AD converter 18, and through the voltage signal of a2 end earlier through signal average circuit 17, after realizing the average of humidity voltage signal handled, send into again and carry out the collection of signal digital amount in the AD converter 18.
Single-chip microcomputer 19 reads after the digital signal of AD converter 18 outputs, according to the ratio of 0～5V after the calibration computing of inside, be converted to corresponding water percentage numerical value, drive and show at the enterprising line number word of liquid crystal display 21 (LCD1602), Ding Biao method can be divided linear calibration and nonlinear calibration herein, specific as follows: during linear scaled, if the water percentage of tested material changes between 0～max%, if the voltage signal that collects is 5V, then output is shown as water percentage max%, if the voltage signal that collects is 0V, then output is shown as water percentage 0%, and all the other signals are pressed linear scaling output water percentage; For some material, its mixing voltage signal and material water ratio are nonlinear relationship, need to calibrate in the measurement debug phase earlier, the corresponding relation of test each voltage signal and material water ratio value between 0～5V of preposition instrument amplifier 7 outputs, different voltages of storage and material water ratio are the storehouse (being two-dimensional array) of one-to-one relationship in single-chip microcomputer, like this when measuring, after voltage signal is gathered in AD converter 18, the inquiry that can carry out in above-mentioned storehouse by single-chip microcomputer obtains the water percentage size of material.
Digital signal is sent into the signal output mode with the form of analog voltage signal and is selected circuit 23 behind DA converter 22; Single-chip microcomputer is by the detection to model selection control button 20, and it is voltage or current-mode that the control output mode is selected the way of output of circuit 23; Finally, by voltage or the current analog signal that output mode selects circuit 23 to export, export through the simulation output wiring terminal Sig and the GND of moisture signal display control terminal 9 front consoles.
(I), (J), (K) are illustrated respectively in and measure water percentage when being 0%～15% sand among Figure 10, after moisture signal display control terminal 9 internal circuits are handled, final output mode synoptic diagram, when 0～5V output mode selection key of moisture signal display control terminal 9 front consoles is pressed, among output mode synoptic diagram such as the figure (I), water percentage finally characterizes output by aanalogvoltage linearly; When (J), (K) represent respectively to select 0～10V and 4～20mA output mode in the synoptic diagram, the output signal of final signal.As seen from Figure 10, after moisture signal display control terminal 9 processing of circuit, the water percentage of material is finally with voltage or the linear output of current forms, for subsequent control processing in the industrial and agricultural production measurement provides convenience.
During design, the STC89C52RC that single-chip microcomputer 19 selects for use macrocrystalline science and technology to produce; The PCF8591P that the AD/DA chip selects for use the design of PHILIPS company to produce, this chip are that iic bus drives, and possess AD and DA translation function simultaneously, can effectively improve the one-chip machine port utilization rate; About the concrete type of drive of single-chip microcomputer STC89C52RC, AD/DA conversion chip PCF8591P, liquid crystal display LCD1602 is connected with interlock circuit, in its chip explanation document separately, detailed description is all arranged, no longer narration herein.
In sum, the present invention has designed a kind of reflection type microwave hygrometric device based on frequency mixing technique.Apparatus system can be realized the high precision noninvasive measurement to material water ratios such as grain moisture content, concrete humidity, tobacco moisture percentage, weaving chemicals water cut, applied range.The present invention has the advantage of following several respects: one, the frequency mixing technique with microwave transmitted wave and reflection wave is applied in the moisture measurement, adopts single microwave transmitting and receiving waveguide multiplexing, makes the device design simplification; Two, the device outer wall is designed to stainless steel structure, and the microwave transmitting and receiving end is designed to ceramic structure, and the microwave transmitting and receiving probe is embedded in the stainless steel barrel by volution, suppresses the interference of noise signal effectively, and makes the device scope of application wider; Three, the device signal processing circuit has designed multiple signal sampling pattern and output mode, possesses simultaneously to regulate at sensitivity adjusting and zero point, effectively satisfies the demand that control is measured in industrial and agricultural production.
Description of drawings
Fig. 1. reflection type microwave hygrometric device sonde configuration figure;
Fig. 2. microwave local oscillation and reflected signal mixing schematic diagram;
Fig. 3. the main spectrogram of mixed frequency signal;
Fig. 4. wave-guide cavity wave oscillator and radiating guide synoptic diagram;
Fig. 5. signal processing circuit functions of modules block diagram;
Fig. 6. the mixing intermediate-freuqncy signal is with sand water percentage variation relation figure;
Fig. 7. preposition instrument is amplified the zeroing circuit schematic diagram;
Fig. 8. signal average treatment circuit schematic diagram;
Fig. 9. the signal output mode is selected circuit theory diagrams.
Figure 10. microwave is surveyed moisture signal processing flow synoptic diagram
Embodiment
Embodiment 1: the concrete structure of device probe
In the present embodiment, realize the measurement of water-content coefficient to construction sand, the water percentage of sand directly influences the concrete in the building and the interpolation ratio of water, and then influences the soundness of whole building.
Material 1 to be measured is the building sand of certain water percentage, and sand bed thickness is not less than 10cm.During hygrometric, potsherd 2 is close to sand bed, and its diameter is 80mm, and thickness 6mm is stupalith.3 of potsherd 2 and stainless steel outer walls are fixed with glue, the external diameter 89mm of stainless steel cylinder 3, internal diameter 81mm, wall thickness 4mm, length 30cm.Microwave transmitting and receiving waveguide 4 is an aluminum alloy materials, its bore D1=45mm, and D2=32mm, length is 45mm.Microwave cavity oscillator 6 is the waveguide of standard BJ-100 type, is of a size of L1=22.9mm, L2=10.2mm, and the frequency of the hygrometric microwave local oscillation signal of generation is 10.525GHz, and power is 20mW, and continuous-current excitation voltage is 8V.
Fig. 6 has shown that when the vertical range of regulating microwave transmitting and receiving waveguide 4 and ceramic panel 2 is 15mm the voltage signal of microwave cavity oscillator 6 outputs at room temperature is with the variation relation of sand water percentage.
The one side design when making sheet of preposition instrument magnification circuit plate 7 has a pair of screw via hole, pitch of holes 40mm, and aperture 4mm is fixed on the interior wall bracket of stainless steel base 8 with screw during installation.Stainless steel base 8 is half arc, and its sidepiece is provided with screw thread, can tighten to be fixed in stainless steel cylinder 3 rear portions.Signal wire and power lead pass stainless steel base 8 centers, draw by aviation plug, are connected to moisture signal display control circuit 9 inside of front end.
Embodiment 2: preposition instrument is amplified the zeroing circuit design proposal
Fig. 7 is preposition instrument amplifier circuit 7, circuit function is that the hygrometric voltage signal is returned to zero and amplifies, be that the voltage signal amplitude changes between 0～5V, requiring herein in the design, circuit possesses the characteristics that the high and low noise of precision is introduced of amplifying, in this circuit, the AD620 that instrument amplifier A3 selects for use ADI to produce.By the voltage signal Si of microwave cavity oscillator 6 output by instrument amplifier A3+IN holds input ,-IN holds ground connection; Slide rheostat R14 cooperates with resistance R 13 gain amplifier of instrument amplifier A3 is regulated; Potentiometer R11 and R10, R12 are connected on the positive-negative power two ends jointly, behind voltage follower A4, for instrument amplifier A3 provides the zeroing bias voltage.
On device was chosen, resistance R 10, R12 resistance size were 1M Ω, and potentiometer R11 size is 500K Ω, and the adjustable bias voltage range is ± 5V, and the A4 model is the OP07 that ADI produces, and R13 is 1.8K Ω, and slide rheostat R14 size is 5K Ω; At signal output part, R15 and C4 constitute low-pass filter unit, and the R15 resistance is 10K Ω, and C4 is 0.1 μ; The supply voltage of circuit chips is positive and negative 15V, positive and negative pin 7 and 4 ends that meet amplifier A3 and A4 respectively.
Embodiment 3: signal average treatment circuit design proposal
Fig. 8 is a signal average treatment circuit 17, its design philosophy is to utilize the mode of precision resistance dividing potential drop with the input signal step-down earlier, adopt slow integral way that this signal is carried out integration summation in time again, by single-chip microcomputer integrated signal is carried out periodic sampling and resets at last, output mean value.
Particularly, in Fig. 8, it is that signal bleeder circuit module (is made up of fixed resistance R6, adjustable resistance R5 and amplifier A2 that signal average treatment circuit 17 is divided into three module: M1, M2 is that (be made up of resistance R 1, R2, R3, R4 and amplifier A1, M3 is integration reset circuit module (being made up of NPN type switch triode Q1, integrating capacitor C1) to integration match circuit module.
M1 is a signal bleeder circuit module, voltage signal through the a2 of relay 16 end is introduced S1, S1 connects the end of fixed resistance R6, the stiff end of another termination adjustable resistance R5 of fixed resistance R6, another stiff end ground connection of adjustable resistance R5, the positive input of the adjusting termination amplifier A2 of adjustable resistance R5, the negative input of amplifier A2 links to each other with amplifier A2 output terminal, realizes the voltage follow function;
M2 is an integration match circuit module, the output terminal of amplifier A2 is connected to an end of resistance R 3 in the M1 module, the R3 other end is connected to the positive input of amplifier A1, resistance R 1 is connected across between the output terminal S3 of the negative input of amplifier A1 and amplifier A1, resistance R 2 is connected across between the positive input and output terminal S3 of amplifier A1, the end of the negative input connecting resistance R4 of amplifier A1, the other end ground connection of resistance R 4 is delivered to AD modular converter 18 by output terminal S3 output earth signal;
M3 is an integration reset circuit module, the base stage S2 of NPN type switch triode Q1 connects single-chip microcomputer 19 pulse signal originating ports in this part, the emitter of triode Q1 is connected on the end of integrating capacitor C1, while ground connection, the collector of triode Q1 is connected on the other end of integrating capacitor C1, and the collector of triode Q1 output simultaneously is connected to the positive input of amplifier A1 among the integration match circuit module M2.
During circuit working, voltage signal is by the input of S1 end, after signal bleeder circuit module M1 step-down, signal carries out integration in capacitor C 1 place in integration reset circuit module M3, after single-chip microcomputer 19 timer internals are finished determined integral time (this circuit is set at 10S), the 18 output terminal S3 at integration match circuit module M2 carry out data acquisition by single-chip microcomputer 19 control AD modular converters, after collection is finished, sending reset pulse by single-chip microcomputer 19 imports from port S2, make switch triode Q1 conducting, realization resets to integrating capacitor C1's, and next integration period begins immediately.
On device is chosen, divider resistance R6 resistance is 51K Ω, adjustable resistance R5 size is 10K Ω, amplifier A2 model is the OP07 that ADI produces, resistance R 1 in the integrating circuit, R2, R3, the R4 resistance is 10M Ω, integrating capacitor C1 selects CBB electric capacity for use, size 0.1 μ, it is NPN type 8050 that switch triode Q1 selects model for use, at the S2 port, sent into by the every interval 10S of single-chip microcomputer 19 control waves capacitor discharge is resetted, the LF411 that integrating amplifier A1 selects for use National Semiconductor to produce, its low-leakage current and low temperature characteristics such as float are fit to slow integration and amplify.The supply voltage of circuit chips is positive and negative 15V, positive and negative pin 7 and 4 ends that meet amplifier A1 and A2 respectively.
The dividing potential drop position of adjustable resistance R5 is relevant with the integrating circuit integration constant, a kind of definite method is at circuit S1 end input 3V d. c. voltage signal, is the 5V direct impulse signal in cycle in the input of S2 end with 10S, pulsewidth 10ms, regulate adjustable resistance R5, measure S3 port output voltage peak value simultaneously, when the big value stabilization of S3 output electrode during at 3V, the position of R5 determines, this moment, circuit can be realized the voltage signal of the input output of averaging continuously in the 10S.
Embodiment 4: the signal output mode is selected the circuit design scheme
Fig. 9 is that the signal output mode is selected circuit 23, and for satisfying the industrial measurement and control demand to material water ratio, this module provides the output of 4～20mA electric current, the output of 0～5V voltage, three kinds of patterns of 0～10V voltage output.Among the figure, the AD694 that chip U1 selects for use ADI to produce, this chip can realize the voltage signal of input is converted to current signal output; Analog voltage signal through 22 outputs of DA converter is imported by the 3rd pin of U1; The 9th pin control output mode of chip U1, when being low level, 11 pins output, 4～20mA electric current, when 9 pins are supply voltage, 11 pins output, 0～16mA electric current; Resistance R 7, R8 are divider resistance, can be 0～5V or the output of 0～10V voltage with himself the 0～16mA current conversion of flowing through; Chip protection diode D1 reversal connection is in input end SI and power end, and the D2 reversal connection is in output terminal SO and ground end; The D3 reversal connection is in power end and ground end; Filter capacitor C2 connects between output terminal SO and the ground, and C3 connects between power supply and the ground.
Particularly, the model of diode D1, D2, D3 is 1N4007; Resistance R 9 resistance 51K Ω, R7, R8 are the precision resistance of resistance 312 Ω; Capacitor C 2 is the ceramic disc capacitor of 0.01 μ, and C3 is 0.1 μ ceramic disc capacitor; The positive 15V power supply of 13 pins of chip AD694,5 pin ground connection.
In output control, succeed electrical equipment in the circuit between K1, K2, K3 and the ground respectively, break-make by single-chip microcomputer 19 pilot relays, K1, K2, K3 have and have only an end ground connection simultaneously during circuit working, when K1 ground connection, the moisture information of material is exported by SO with 4～20mA current forms, and SO is 0～5V voltage output mode during K2 ground connection, SO output 0～10V voltage during K3 ground connection; Output port SO finally links to each other with the front console Sig binding post of display control terminal 9.
Claims (9)
1. the reflection type microwave based on frequency mixing technique is surveyed the water percentage device, it is characterized in that:
1) forms by being installed on stainless steel cylinder (3) interior horn-like microwave transmitting and receiving waveguide (4), microwave cavity oscillator (6), being fixed in the preposition instrument magnification circuit plate (7) on stainless steel cylinder (3) back seat (8) inwall and being arranged on the outside moisture signal display control terminal (9) of stainless steel cylinder (3);
2) microwave transmitting and receiving waveguide (4) is installed on the inwall of stainless steel cylinder (3) by volution (5);
3) microwave cavity oscillator (6) is installed in the rear end of microwave transmitting and receiving waveguide (4), produce the microwave local oscillation signal of corresponding survey frequency, and export the direct current mixing voltage signal that comprises the tested material moisture information after the echoed signal of tested material (1) reflection and the microwave local oscillation signal mixing low-pass filtering;
4) front end at stainless steel cylinder (3) is equipped with potsherd (2), and potsherd (2) is close to tested material (1) to reach pinpoint accuracy;
5) direct current mixing voltage signal is after preposition instrument amplifying circuit (7) amplifies, be sent to moisture signal display control terminal (9), again this direct current mixing voltage signal is carried out subsequent treatment on the circuit, thereby on the LCDs of moisture signal display control terminal (9), show the moisture of tested material.
2. a kind of reflection type microwave based on frequency mixing technique as claimed in claim 1 is surveyed the water percentage device, it is characterized in that:
1) signal input moisture signal display control terminal (9) selects circuit (23) to form by supply module (15), relay (16), signal average circuit (17), AD converter (18), single-chip microcomputer (19), model selection control button (20), liquid crystal display (21), DA converter (22), output mode;
2) the direct current mixing voltage signal of microwave cavity oscillator (6) output is after preposition instrument amplifier (7) zeroing is amplified, and it is the voltage signal that 0～5V changes that moisture signal is modulated to amplitude; Behind this voltage signal input moisture signal display control terminal (9), at first passing through relay (16) judges, this relay is by single-chip microcomputer (19) control, and single-chip microcomputer (19) is controlled this relay and connected a1 end or a2 end according to the difference input of model selection control button (20); Voltage signal through a1 end is directly sent into AD converter (18), and through the voltage signal of a2 end earlier through signal average circuit (17), after realizing the average of humidity voltage signal handled, send into again and carry out the collection of signal digital amount in the AD converter (18);
3) single-chip microcomputer (19) reads after the digital signal of AD converter (18) output, after the calibration computing of inside, is converted to corresponding water percentage numerical value according to the ratio of 0～5V, drives and carries out numeral demonstration at liquid crystal display (21);
4) digital signal is sent into the signal output mode with the form of analog voltage signal and is selected circuit (23) behind DA converter (22); Single-chip microcomputer is by the detection to control button (20), and it is voltage or current-mode that the control output mode is selected the way of output of circuit (23); Finally, select the voltage or the current analog signal of circuit (23) output by output mode.
3. a kind of reflection type microwave based on frequency mixing technique as claimed in claim 2 is surveyed the water percentage device, it is characterized in that: described signal average treatment circuit (17),
1) by signal bleeder circuit module M1, integration match circuit module M2 and integration reset circuit module M3 form, it is to utilize the mode of precision resistance dividing potential drop with the input signal step-down earlier, adopt slow integral way that this signal is carried out integration summation in time again, by single-chip microcomputer (19) integrated signal is carried out periodic sampling and resets the mean value of output voltage signal at last;
2) signal bleeder circuit module M1, form by fixed resistance R6, adjustable resistance R5 and amplifier A2, voltage signal through relay (16) a2 end is introduced S1, S1 connects the end of fixed resistance R6, the stiff end of another termination adjustable resistance R5 of fixed resistance R6, another stiff end ground connection of adjustable resistance R5, the positive input of the adjusting termination amplifier A2 of adjustable resistance R5, the negative input of amplifier A2 links to each other with amplifier A2 output terminal, realizes the voltage follow function;
3) integration match circuit module M2, by resistance R 1, R2, R3, R4 and amplifier A1 form, the output terminal of amplifier A2 is connected to an end of resistance R 3 in the signal bleeder circuit module M1 module, the R3 other end is connected to the positive input of amplifier A1, resistance R 1 is connected across between the output terminal S3 of the negative input of amplifier A1 and amplifier A1, resistance R 2 is connected across between the positive input and output terminal S3 of amplifier A1, the end of the negative input connecting resistance R4 of amplifier A1, the other end ground connection of resistance R 4 is delivered to AD modular converter (18) by output terminal S3 output earth signal;
4) integration reset circuit module M3, form by NPN type switch triode Q1, integrating capacitor C1, the base stage S2 of NPN type switch triode Q1 connects single-chip microcomputer (19) pulse signal originating port, the emitter of triode Q1 is connected on the end of integrating capacitor C1, while ground connection, the collector of triode Q1 is connected on the other end of integrating capacitor C1, and the collector of triode Q1 output simultaneously is connected to the positive input of amplifier A1 among the integration match circuit module M2;
5) voltage signal is after signal bleeder circuit module M1 step-down, signal carries out integration in capacitor C 1 place in integration reset circuit module M3, single-chip microcomputer (19) timer internal is after determined integral time, 10s finished, carry out data acquisition by single-chip microcomputer (19) control AD modular converter (18) at the output terminal S3 of integration match circuit module M2, after collection is finished, sending reset pulse by single-chip microcomputer (19) imports from port S2, make switch triode Q1 conducting, realization resets to integrating capacitor C1's, and next integration period begins immediately.
4. a kind of reflection type microwave based on frequency mixing technique as claimed in claim 3 is surveyed the water percentage device, it is characterized in that: at circuit S1 end input 3V d. c. voltage signal, is the 5V direct impulse signal in cycle in the input of S2 end with 10S, pulsewidth 10ms, regulate adjustable resistance R5, measure S3 port output voltage peak value simultaneously, when S3 output voltage maximum value is stabilized in 3V, determine the position of variable resistor R5, this moment, circuit can be realized the continuously voltage signal of the input output of averaging in the 10s.
5. a kind of reflection type microwave based on frequency mixing technique as claimed in claim 2 is surveyed the water percentage device, it is characterized in that: model selection control button (20) is arranged on the panel of moisture signal display control terminal (9), the upper left side of panel is provided with LCDs, shows material water ratio numerical value; The below of display screen is provided with Sig and two binding posts of GND, and the simulation output of water percentage signal is provided; The upper right side of panel is provided with " in real time ", " average " model selection control button (20), is used for controlling the sampling processing pattern of internal circuit, and when respective keys was pressed, internal circuit can drive the LED lamp that is positioned at the button top, makes it to light; The bottom righthand side of panel is provided with " 4～20mA ", " 0～5V ", " 0～10V " model selection control button (20), is used for controlling the output mode of water percentage signal, and each button top has the LED lamp to indicate the output mode of current device equally.
6. a kind of reflection type microwave based on frequency mixing technique as claimed in claim 5 is surveyed the water percentage device, it is characterized in that: when model selection control button (20) was " in real time " pattern, single-chip microcomputer (19) pilot relay (16) was connected the a1 end; When model selection control button (20) was " average " pattern, single-chip microcomputer (19) pilot relay (16) was connected the a2 end.
7. a kind of reflection type microwave based on frequency mixing technique as claimed in claim 1 is surveyed the water percentage device, it is characterized in that: stainless steel cylinder (3) wall thickness 3～7mm, external diameter 75～120mm, potsherd (2) thickness 4～10mm, diameter 70～110mm; By the rotation of volution (5), the front and back adjustable distance of microwave transmitting and receiving waveguide (4) is between 10～50mm; The inside and outside volution phase interlock of volution (5), external diameter 70～110mm, volution adjustable length are 10～50mm.
8. a kind of reflection type microwave based on frequency mixing technique as claimed in claim 1 is surveyed the water percentage device, it is characterized in that: microwave transmitting and receiving waveguide (4) is made by alloy material or metal-coated membrane material, the wide D1 of its front end is 40mm～50mm, high D2 is 30mm～40mm, length is between 40mm～50mm, and the size of rear end size and microwave cavity oscillator (6) is complementary; The wide L1 of microwave cavity oscillator (6) is 22.9mm, and high L2 is 10.2mm, and the frequency of the microwave intrinsic signals of generation is 10.525GHz, and power is 20mW, and the continuous-current excitation voltage of microwave cavity oscillator is 8V.
9. a kind of reflection type microwave based on frequency mixing technique as claimed in claim 1 is surveyed the water percentage device, it is characterized in that: volution and outer volution two parts in volution (5) comprises, be rubber or plastic material, interior volution sticks with glue in the outside of microwave transmitting and receiving waveguide (4), outer volution sticks with glue in the inwall of stainless steel casing (3), interior volution and the mutual interlock of outer volution.
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