CN102262096B - 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 impact to performance quality and the production efficiency of product, and this is comprising the processing and manufacturings such as grain, tobacco, paper, coal stone, soil, chemical fertilizer, weaving, concrete and oil industry.The material water ratio Standard General is used the wet basis method and is calculated, namely by measure its dry before with dry after the proportion of difference of weight try to achieve.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. are different.
In some occasion, require the water percentage of online nondestructive measurement material, and then realize that whole production process is carried out line closed loop to be controlled, this just has higher requirement to humidity measuring method.Microwave Detecting Technology is a new technology that grows up on the bases such as microwave electronics and Microwave Measurement Technique, due to medium, microwave there are the physical characteristicss such as reflection, transmission, scattering, resonance and Doppler effect, can interact by mode and the medium of space radiation, in measuring process, sensor can not contact with measured matter, 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 the compound dielectric in microwave field by it.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 material will affect its specific inductive capacity significantly, therefore measure the physical quantitys relevant to specific inductive capacity such as power attenuation by the microwave of material, phase place variations, resonance frequency, just can indirectly record this Moisture in Material how much.
Microwave detection method can be divided into space wave method, Transmission line method resonant cavity method at present, and wherein rear two kinds of methods are suitable for contact type measurement, unsuitable on-line measurement.For the space wave method, different from the measured medium action mode according to microwave, can divide transmission-type and reflective two kinds, its principle is by measuring microwave and measured medium transmissive portion or reflecting part amplitude, phase place size and change after space behavior, reflecting that indirectly material water ratio is big or small.
Reflection type microwave humidity-measuring device due to its transceiver, is easy to install, and the characteristics such as be not subjected to that material thickness affects are convenient to be applied to detect on production line online.At present both at home and abroad on the reflection type microwave humidity-measuring sensor design, morely adopt emission and receive isolatedly, namely via microwave devices such as isolator, circulators, microwave source and reflection echo signal are isolated between microwave source and detection tube, detect separately.Because this sonde configuration is more complicated, easily introduce noise, the shortcoming such as cost is higher 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 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 humidity-measuring device based on frequency mixing technique.Its structure is simple and clear, easy operating, and measuring accuracy is high, scope is wide, and antijamming capability is strong, can realize can't harm online continuous coverage, and cost is lower, has broad application prospects 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 frequency of microwave local oscillation signal and echoed signal equates (microwave transmitting and receiving waveguide 4 relative with tested material 1 position fixedly time), 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 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 stainless steel cylinder 3, preposition magnifier plate 7, the moisture signal display control terminal 9 that is fixed on stainless steel cylinder 3 back seat 8 inwalls forms; Microwave transmitting and receiving waveguide 4 is arranged on the inwall of stainless steel cylinder 3 by volution 5; Microwave cavity oscillator 6 is arranged on 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 with after the echoed signal of tested material 1 reflection and microwave local oscillation signal mixing low-pass filtering the direct current mixing voltage signal that comprises the tested material moisture information; 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 magnifier 7 amplifies, be sent to moisture signal display control terminal 9, again this direct current mixing voltage signal is carried out subsequent treatment on circuit, thereby in the moisture of the liquid crystal display screen display tested material of moisture signal display control terminal 9.
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 magnifier 7 amplifies is after the internal circuit of moisture signal display control terminal 9 is processed, the numerical value that is shown tested material 1 water percentage by LCDs, voltage or the current analog signal relevant to tested material 1 water percentage of analog signal output interface output simultaneously.
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 schematic diagram, Fig. 1 (b) is the device appearance schematic diagram; The 1st, tested material can be typically the not material of metal impurities 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 and tested material Range-based.Volution 5 comprises interior volution and outer volution two parts, is rubber or plastic material, and 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, field applied according to the hygrometric device is different, need the interior volution of manual rotation 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, be screwed inside and outside volution, the position of microwave transmitting and receiving waveguide 4 is fixed.The optimum sensitivity method for determining position, relevant with the sensor output voltage signal waveform, will be illustrated 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; The inside and outside volution phase interlock of volution 5, 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.
In Fig. 4, figure (c) is the microwave cavity oscillator 6 that adopts in practical application, and figure (d) is the schematic appearance of microwave transmitting and receiving waveguide 4.In order to make the microwave equipment working stability low-cost, the microwave cavity oscillator of selecting Zhejiang connection letter Electronics Equipment Co., Ltd to produce in design, realize the emission of microwave local oscillation signal and 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 that frequency stabilization, harmonic wave are little, the DC low-voltage power supply.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 by oscillating diode, wave-guide cavity wave, adjusting screw and is determined.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.
In 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 that voltage bias and the matched impedance of normal operation are 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 is placed in 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 sensitive element, so the stability requirement to voltage is higher, hold to the DC voltage of 8V and reference by (8V), (GND) two lines inputs, mixed frequency signal is by the output of (Si) line, and power lead and signal wire are connected to an end of preposition magnifier plate 7.
The present invention is applied to the microwave mixer technology in 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 namely 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
0The direct current biasing that applies for satisfying normal mixing Q value; D1 is the Schottky mixer diode, in circuit is namely 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)
The echoed signal that receives in actual measurement and local oscillation signal are in a ratio of a small voltage increment, can with the loop signal electric current in each working point expansion in Taylor series, further embody the mixed frequency signal frequecy characteristic:
In expansion, first is to flow through the large-signal of diode under local oscillator excitation, comprises DC terms, local oscillation signal first-harmonic and harmonic term thereof.In formula, other are as echoed signal U
SHour be the small-signal composition, can only get second, at this moment:
G in 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
Therefore after local oscillator and Dc bias size was determined, the electricity of mixer diode was led and is fixed value.
Fig. 3 draws each frequency spectrum analysis chart by (4) formula analysis, and the line segment height namely represents this frequency signal size relative value.(4) in formula during for n=1, the frequency item is ω
L-ω
S, i.e. ω in 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, in formula, the mixing electricity is led g
1Be constant, U
SThe reflection echo amplitude, matter water-containing rate and the positive correlation of microwave reflection echo amplitude, φ is reflection echo phase place relative value, its size is the periodic function of microwave probe and material reflecting interface distance, every mobile half wavelength distance, the φ value changes one-period.
In the actual hygrometric process of above derivation explanation, can be with mixed frequency signal by after 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 microwave reflection face, measure the microwave cavity oscillator (amplitude of voltage signal (Si) line of 6 outputs with voltage table simultaneously, in amplitude reaches one-period during maximum value, probe namely is in the optimum sensitivity position.The different amplitudes of output direct current signal namely reflect the size of the corresponding water percentage of material.
In Fig. 1,7 is preposition instrument amplifier circuit parts, and this part is positioned over stainless steel cylinder inside, and effect is that the direct current mixing voltage signal to 6 outputs of microwave cavity oscillator returns to zero and amplifies.In 200～500mV left and right, after 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, suppress the common-mode noise ability strong, and possess adjusting at zero point and adjustment of sensitivity function, some Common Instrument amplifiers are available, as AD620, the AD627 etc. of ADI.In the equipment debugging stage, different according to the field of application of installation measuring moisture, after determining microwave transmitting and receiving waveguide 4 and reaching the position of optimum measurement sensitivity, need to return to zero and enlargement factor is regulated to this preposition magnifier 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 is surveyed moisture signal processing flow schematic diagram, has reflected the signal processing model of the unit such as reception, microwave mixer, low-pass filtering output and zeroing amplification of emission, the echoed signal of microwave.
In Figure 10 (e), launched microwave and reception echo represent respectively the microwave of being launched by microwave transmitting and receiving waveguide 4 and the echoed signal that receives, and microwave frequency is all 10.5GHz, receive the amplitude of echo much smaller than the amplitude of emission echo; After mixer diode 11 mixing in microwave cavity oscillator 6, the main frequency spectrum of mixed frequency signal is as shown in (f) in figure, because the frequency of two signals that participate in mixing is identical, so in frequency spectrum (f), required intermediate-freuqncy signal is that frequency is the direct current signal of 0Hz, and in frequency spectrum, 10.5GHz and 21GHz item are original signal frequency and frequency-doubled signal frequency; After the inner low-pass filtering of microwave cavity oscillator 6, high-frequency signal in mixing frequency spectrum (f) is filtered, in figure, (g) expression is that 0%～15% sand is when testing to water percentage, the Si end output schematic graph of microwave cavity oscillator 6, in water percentage was 0%～15% scope, the variation range of output signal was in 1V; After modulation is amplified in preposition magnifier 7 zeroings, the output mode of signal is as shown in figure (h), and when changing in the scope of tested moisture content 0%～15%, preposition magnifier 7 output signals are crossed 0 point, maximal value is 5V, and between 0～5V monotone variation.
After 7 modulation of preposition magnifier, the voltage signal of amplification is drawn by base 8 centers through wire, delivers to the moisture signal display control terminal 9 of front end; The wire 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 control of signal sampling and output mode, and the concrete water cut of material is shown with the numerical value formal intuition, and the simulated data output port is provided simultaneously.
The Appearance Panel of moisture signal display control terminal 9 is as shown in (b) in 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 ", button 20 is controlled in " average " model selection, 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 ", button 20 is controlled in " 0～10V " model selection, is used for controlling the output mode of water percentage signal, and the output mode of the current device of LED lamp indication is arranged above each button equally.
Particularly, the following dual mode of signal sampling design: (1) is for satisfying the Monitoring and Controlling requirement in commercial production control, and the signal real-time sampling output mode of design, the humidity of materials voltage signal is exported take 0.3s as cycle detection, when " in real time " button in panel was pressed, this pattern started; (2) for satisfying the signal average output mode that in industrial and agricultural production, on-line continuous measurement requirement designs, side circuit is realized the moisture signal of continuous coverage is carried out average value processing, and export the medial humidity of the material of being surveyed in this section Measuring Time take 10s as a cycle, this pattern is started by key control by " average " in panel.
On the signal output mode is selected, for the different water cut that the makes material form by curtage characterizes, circuit is designed with respectively 4～20mA, 0～5V, three kinds of different curtage output modes of 0～10V, 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 the moisture signal display control terminal 9 front console Sig of place and two binding post outputs of GND for the successive projects technician carries out the moisture signal-data processing.
Particularly, Fig. 5 is the interior signal processing circuit functions of modules block diagram of 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; After signal input moisture signal display control terminal 9, at first through relay 16 judgements, this relay is controlled by single-chip microcomputer 19, single-chip microcomputer is controlled the difference input of button 20 according to model selection, control this relay and connect a1 end (associative mode is selected to control button and selected " in real time " pattern) or a2 end (associative mode is selected to control button and selected " average " pattern); Voltage signal through the a1 end is directly sent into AD converter 18, and first through signal average circuit 17 through the voltage signal of a2 end, after realizing the average value processing to the humidity voltage signal, then sends into and carries out the collection of signal digital amount in 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), the method of calibration 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, output display is water percentage max%, if the voltage signal that collects is 0V, output display is water percentage 0%, 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 first to calibrate in the measurement debug phase, the corresponding relation of test each voltage signal and material water ratio value between 0～5V of preposition instrument amplifier 7 outputs, the 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 gathers 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 after DA converter 22; Single-chip microcomputer is by controlling the detection of button 20 to model selection, the way of output of controlling output mode selection circuit 23 is voltage or current-mode; Finally, selected voltage or the current analog signal of circuit 23 outputs by output mode, through simulation output wiring terminal Sig and the GND output of moisture signal display control terminal 9 front consoles.
In Figure 10, (I), (J), (K) are illustrated respectively in and measure water percentage when being 0%～15% sand, after moisture signal display control terminal 9 internal circuits are processed, final output mode schematic diagram, when 0～5V output mode selection key of moisture signal display control terminal 9 front consoles is pressed, in output mode schematic diagram such as figure (I), water percentage finally characterizes output by aanalogvoltage linearly; When in schematic diagram, (J), (K) represent respectively to select 0～10V and 4～20mA output mode, 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 processed for subsequent control in the industrial and agricultural production measurement convenience is provided finally with voltage or the linear output of current forms.
During design, the STC89C52RC that single-chip microcomputer 19 selects macrocrystalline science and technology to produce; The PCF8591P that the AD/DA chip selects the design of PHILIPS company to produce, this chip are that iic bus drives, and possess simultaneously AD and DA translation function, 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, all be described in detail in its chip specification documents separately, herein no longer narration.
In sum, the present invention has designed a kind of reflection type microwave humidity-measuring 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 advantages of following several respects: one, the frequency mixing technique with microwave transmitted wave and reflection wave is applied in 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, effectively suppresses the interference of noise signal, and makes the device scope of application wider; Three, the device signal processing circuit has designed multi-signal sampling pattern and output mode, possesses simultaneously to regulate at adjustment of sensitivity and zero point, effectively satisfies industrial and agricultural production and measures the demand of controlling.
Description of drawings
Fig. 1. reflection type microwave humidity-measuring 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 schematic diagram;
Fig. 5. signal processing circuit functions of modules block diagram;
Fig. 6. the mixing intermediate-freuqncy signal is with moisture content variation relation figure;
Fig. 7. preposition instrument is amplified the zeroing circuit schematic diagram;
Fig. 8. signal average value processing circuit theory diagrams;
Fig. 9. the signal output mode is selected circuit theory diagrams.
Figure 10. microwave is surveyed moisture signal processing flow schematic 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 affects concrete in building and the interpolation ratio of water, and then affects the soundness of whole building.
Fig. 6 has shown that when the vertical range of the waveguide 4 of adjusting microwave transmitting and receiving and ceramic panel 2 was 15mm, the voltage signal of at room temperature microwave cavity oscillator 6 outputs was with the variation relation of moisture content.
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, that the voltage signal amplitude changes between 0～5V, requiring herein in 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 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 coordinates with resistance R 13 gain amplifier of instrument amplifier A3 is regulated; Potentiometer R11 and R10, R12 are connected on positive-negative power two ends jointly, after 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 consist of 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 respectively amplifier A3 and A4.
Embodiment 3: signal average value processing circuit design scheme
Fig. 8 is signal average value processing circuit 17, its design philosophy is first to utilize the mode of precision resistance dividing potential drop with the input signal step-down, adopt again slow integral way to carry out integration summation in time to this signal, 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 comprised of fixed resistance R6, adjustable resistance R5 and amplifier A2 that signal average value processing circuit 17 is divided into three module: M1, M2 is that (be comprised of resistance R 1, R2, R3, R4 and amplifier A1, M3 is integration reset circuit module (being comprised of NPN type switch triode Q1, integrating capacitor C1) to the integration matching circuit module.
M1 is 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 is connected with amplifier A2 output terminal, realizes the voltage follow function;
M2 is the integration matching circuit module, in the M1 module, the output terminal of amplifier A2 is connected to an end of resistance R 3, 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 the integration reset circuit module, in this part, the base stage S2 of NPN type switch triode Q1 connects single-chip microcomputer 19 pulse signal originating ports, 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 in integration matching circuit module M2.
during circuit working, voltage signal is by the input of S1 end, after signal bleeder circuit module M1 step-down, signal capacitor C 1 place in integration reset circuit module M3 carries out integration, after single-chip microcomputer 19 timer internals are completed determined integral time (this circuit is set as 10S), control the AD modular converter 18 output terminal S3 at integration matching circuit module M2 by single-chip microcomputer 19 and carry out data acquisition, after collection is completed, sending reset pulse by single-chip microcomputer 19 inputs from port S2, make switch triode Q1 conducting, realization resets to integrating capacitor C1's, 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, in integrating circuit, resistance R 1, R2, R3, the R4 resistance is 10M Ω, integrating capacitor C1 selects CBB electric capacity, size 0.1 μ, it is NPN type 8050 that switch triode Q1 selects model, at the S2 port, being sent at interval of 10S by single-chip microcomputer 19 control waves resets capacitor discharge, the LF411 that integrating amplifier A1 selects National Semiconductor to produce, the characteristics such as its low-leakage current and Low Drift Temperature 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 respectively amplifier A1 and A2.
The dividing potential drop position of adjustable resistance R5 is relevant to the integrating circuit integration constant, a kind of definite method is at circuit S1 end input 3V d. c. voltage signal, at the 5V direct impulse signal of S2 end input take 10S as the cycle, pulsewidth 10ms, regulate adjustable resistance R5, measure simultaneously S3 port output voltage peak value, when the large value stabilization of S3 output electrode during at 3V, the location positioning of R5, this moment, circuit can be realized the continuously voltage signal of the input output of averaging in 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, 0～5V Voltage-output, three kinds of patterns of 0～10V Voltage-output.In figure, the AD694 that chip U1 selects 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 inputted by the 3rd pin of U1; The 9th pin of chip U1 is controlled output mode, when being low level, and 11 pin output 4～20mA electric currents, when 9 pins are supply voltage, 11 pin output 0～16mA electric currents; Resistance R 7, R8 are divider resistance, can be 0～5V or 0～10V Voltage-output 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 ground, and C3 connects between power supply and 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 13 positive 15V power supplies of pin of chip AD694,5 pin ground connection.
On output is controlled, succeed respectively electrical equipment in circuit between K1, K2, K3 and ground, break-make by single-chip microcomputer 19 pilot relays, during circuit working, K1, K2, K3 have and only have an end ground connection simultaneously, when K1 ground connection, the moisture information of material is exported by SO with 4～20mA current forms, and during K2 ground connection, SO is 0～5V Voltage-output pattern, SO output 0～10V voltage during K3 ground connection; Output port SO finally is connected with the front console Sig binding post of display control terminal 9.
Claims (7)
1. the reflection type microwave based on frequency mixing technique is surveyed the water percentage device, it is characterized in that:
1) form 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 magnifier (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 arranged on the inwall of stainless steel cylinder (3) by volution (5);
3) microwave cavity oscillator (6) is arranged on the rear end of microwave transmitting and receiving waveguide (4), produce the microwave local oscillation signal of corresponding survey frequency, and export with after the echoed signal of tested material (1) reflection and microwave local oscillation signal mixing low-pass filtering the direct current mixing voltage signal that comprises the tested material moisture information;
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 magnifier (7) amplifies, be sent to moisture signal display control terminal (9), again this direct current mixing voltage signal is carried out subsequent treatment on circuit, thereby in the moisture of the liquid crystal display screen display tested material of moisture signal display control terminal (9);
6) 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;
The direct current mixing voltage signal of microwave cavity oscillator (6) output is after preposition magnifier (7) zeroing is amplified, and it is the voltage signal that 0～5V changes that the tested material moisture information is modulated to amplitude; After this voltage signal input moisture signal display control terminal (9), at first pass through relay (16) judgement, this relay is controlled by single-chip microcomputer (19), and single-chip microcomputer (19) is controlled the difference input of button (20) according to model selection, controls this relay and connects a1 end or a2 end; Voltage signal through the a1 end is directly sent into AD converter (18), and first through signal average circuit (17) through the voltage signal of a2 end, after realizing the average value processing to voltage signal, then sends into and carries out the collection of signal digital amount in AD converter (18);
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 also and carries out numeral demonstration at liquid crystal display (21);
Digital signal is sent into output mode with the form of analog voltage signal and is selected circuit (23) after DA converter (22); Single-chip microcomputer is by controlling the detection of button (20) to model selection, the way of output of controlling output mode selection circuit (23) is voltage or current-mode; Finally, select circuit (23) output voltage or current analog signal by output mode;
7) signal average circuit (17) is by signal bleeder circuit module M1, integration matching circuit module M2 and integration reset circuit module M3 form, it is first to utilize the mode of precision resistance dividing potential drop with the input signal step-down, adopt again slow integral way to carry out integration summation in time to this signal, by single-chip microcomputer (19), integrated signal is carried out periodic sampling and resets at last, the mean value of output voltage signal;
Signal bleeder circuit module M1, formed 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 is connected with amplifier A2 output terminal, realizes the voltage follow function;
integration matching circuit module M2, by resistance R 1, R2, R3, R4 and amplifier A1 form, in signal bleeder circuit module M1 module, the output terminal of amplifier A2 is connected to an end of resistance R 3, 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, deliver to AD converter (18) by output terminal S3 output earth signal,
Integration reset circuit module M3, formed 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 in integration matching circuit module M2;
Voltage signal is after signal bleeder circuit module M1 step-down, signal capacitor C 1 place in integration reset circuit module M3 carries out integration, single-chip microcomputer (19) timer internal is after determined integral time, 10s completed, control AD converter (18) by single-chip microcomputer (19) and carry out data acquisition at the output terminal S3 of integration matching circuit module M2, after collection is completed, sending reset pulse by single-chip microcomputer (19) inputs from port S2, make switch triode Q1 conducting, realization resets to integrating capacitor C1's, and next integration period begins immediately.
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: at circuit S1 end input 3V d. c. voltage signal, at the 5V direct impulse signal of S2 end input take 10S as the cycle, pulsewidth 10ms, regulate adjustable resistance R5, measure simultaneously S3 port output voltage peak value, 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 10s.
3. 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: model selection is controlled button (20) and 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 ", button (20) is controlled in " average " model selection, 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 ", button (20) is controlled in " 0～10V " model selection, is used for controlling the output mode of water percentage signal, and the output mode of the current device of LED lamp indication is arranged above each button equally.
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: when button (20) was controlled in model selection for " 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.
5. 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.
6. 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.
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: volution (5) comprises interior volution and outer volution two parts, 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 cylinder (3), interior volution and the mutual interlock of outer volution.
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