CN202793963U - Device for synchronously measuring density and moisture content of matrix medium - Google Patents

Abstract

The utility model relates to a device for synchronously measuring density and moisture content of a matrix medium. The device comprises a base and a main circuit board, wherein one side of the base is provided with an upright support rod and a source rod; the lower end of the source rod is provided with a gamma-source chamber; the bottom of the other side of the base is provided with a gamma-ray detector; a handle which is arranged horizontally is connected with the source rod; a moisture content sensor and PCB (Printed circuit board) sealed cabin are arranged in sequence on the gamma-source chamber of the source rod; the moisture content sensor is electrically connected with a moisture content sensor measuring circuit in the PCB sealed cabin; and the moisture content sensor measuring circuit is electrically connected with the main circuit board. The support rod is hollow; the side surface of the support rod is provided with a vertical guide slot; the source rod is arranged inside the support rod; one end of the handle is fixedly connected with the source rod; and the other end of the handle extends out through the vertical guide slot of the support rod and can move up and down along the vertical guide slot. By the device, the density and the moisture content of mediums at different depths can be detected simultaneously at the same place and the device is simple in structure, convenient to operate, safe and reliable.

Description

The device of a kind of synchro measure substrate medium density and moisture

Technical field

The utility model belongs to and utilizes electromagnetic wave or particle radiation to test or the analysis of material technical field, particularly a kind of device that utilizes γ source and electromagnetic wave synchro measure substrate medium density and moisture.

Background technology

Carry out density and moisture on-site measurement for the compacting material take earth, sandstone potpourri etc. as raw material, in the building operation such as Base of Dam of Reservoir construction, railway, highway subgrade, have extensive and important application.The durable stability of the compacted density of matrix and moisture and substrate quality and matrix is closely related, is the quality index of the strict control of two needs.Need in the construction matrix is carried out layered rolling, make the compacted density of matrix and moisture reach corresponding construction quality standard.The effective means of guaranteeing that construction quality is up to standard for the field quick detection that rolls quality.The existing practice is to adopt top layer type nucleon density Moisture Meter that the ground engineerings such as various soil, stone are rolled quality to carry out Site Detection.Top layer type nucleon density Moisture Meter adopts gamma-radiation measuring media density, adopts fast neutron by hydrogen atom slowing down measuring media water cut, and two kinds of methods are with the machine coupling, Simultaneous Determination water cut and Media density.Because the hot of neutron source Am-241-Be and long half life period, its buying, use, keeping is subject to more and more stricter control by the impact of International Terrorism overall situation, and is significant based on the research and development of the determination of moisture method and apparatus of non-neutron source.

United States Patent (USP) (the patent No.: US8071937B2, authorize day: 2011.12.6.) disclose substrate medium density and moisture measuring method, measuring system and computing method based on non-neutron source, measuring system comprises separate density measure part and moisture measurement part, its density measure partly comprises gamma-radiation radiation source and radiation sensor, and moisture measurement partly comprises electromagnetic field generator and electromagnetic sensor.Its computing method partly describe principle and the computing method of electromagnetic measurement moisture in detail.Its density measure part and moisture measurement partly are separate, density measure and moisture measurement process are separated from each other, and moisture measurement only limits to dielectric surface, with regard to how realizing substrate medium density and moisture Simultaneous Determination, the particularly depth of soils based on non-neutron source, do not provide feasible solution such as 20 centimetres of common mensuration to 30 centimetres of depth moisture.

Chinese utility model patent instructions (notification number: CN201035151Y, the day for announcing: 2008.3.12) disclose a kind of nucleon frequency domain moisture-density coupling tester, contain organic block, display screen and CPU surface-mounted integrated circuit, support is provided with liftable gamma-radiation source bar and gamma-radiation detector, also be provided with simultaneously frequency domain moisture detecting head and depression bar assembly, the moisture detecting head is by electrode, high-frequency current generator and electric current output interface form, the depression bar assembly contains depression bar and pressure block, depression bar one end is hinged on the support, pressure block can promote frequency domain moisture measurement probe by depression bar and move downward, thereby probe is entered to carry out water content detection in the soil layer to be measured.This scheme can be measured the content of the certain depth place moisture except the matrix top layer, but still there are the following problems: one, density measure part and moisture measurement part are separate, can not realize substrate medium density and moisture Simultaneous Determination; Two, only have more sharp-pointed moisture probe such as aciculiform detecting head guarantee to go deep into the depth of soils, and measurement all may injure probe at every turn, perhaps needs the probe of special protection.

Summary of the invention

The purpose of this utility model is to provide the device of a kind of synchro measure substrate medium density and moisture, can be at one time, same place realizes substrate medium density and determination of moisture based on non-neutron source, moisture that particularly can the Measurement accuracy depth of soils.

The technical solution that realizes the utility model purpose is: the device of a kind of synchro measure substrate medium density and moisture, comprise base and main circuit board, one side of base is provided with vertical support bar and source bar, γ-source chamber is established in the lower end of source bar, the bottom of the opposite side of base is provided with the gamma-radiation detector, one horizontally disposed handle is connected with the source bar, on the γ of source bar-source chamber, be provided with successively moisture transducer and PCB seal hatch, moisture transducer metering circuit in moisture transducer and the PCB seal hatch is electrically connected, and the moisture transducer metering circuit is electrically connected with main circuit board.

Preferably, support bar is hollow, and the side of support bar has vertical seam guide, and the source bar places in the support bar, and handle one end is fixedly connected with the source bar, and the other end stretches out by the vertical seam guide of support bar, and can move up and down together along this vertical seam guide drive source bar.

Further preferred, the moisture transducer metering circuit forms with being electrically connected like this of main circuit board: the source bar also is hollow, in the bar of the source of hollow, be provided with slide bar, the slide bar upper and lower end parts is subject to handle, can in the scope of both ends, slide up and down with respect to handle, termination lower spring under the slide bar, the lower end of lower spring and PCB seal hatch upper end join, the slide bar upper end connects spring, the top cover of termination support bar on the upper spring, cable is through lower spring, slide bar and upper spring, an end links to each other with the moisture transducer metering circuit through the PCB seal hatch, and the other end links to each other with main circuit board through top cover.

As improvement, the outside of support bar is provided with the vertical side channel that holds cable.

Preferably, upper spring and the lower spring Length Ratio under state of nature is 1:2～4.

Preferably, the length of slide bar is 15～25 centimetres.

As further improvement, sidewall with vertical seam guide relative position on support bar has pilot hole, be provided with the location brake valve in the handle and with the location brake valve trigger of spring, the location brake valve can be combined with pilot hole or separate under the effect of location brake valve trigger.

Preferably, moisture transducer is for being fixed and two cross sections of mutually insulated are the columnar component that circular-arc sheet metal forms by nonmetallic materials.

Another is preferred, and moisture transducer is that the U-shaped metal wire is wrapped on the nonmetal right cylinder, establishes ground wire, not conducting between ground wire and the U-shaped metal wire in the middle of the U-shaped metal wire.

The utility model compared with prior art, its remarkable advantage:

1, convenient, fast: after adopting the structure of the utility model device, along with the source bar gos deep into substrate medium such as soil, gamma-radiation source and go deep into simultaneously substrate medium inside based on non-neutron source moisture transducer, simultaneously disposable substrate medium density and the moisture of recording in same place;

2, simple in structure, easy to operate: and since gamma-radiation source and moisture transducer on same root bar, simple in structure, easy to operate;

3, safety: owing to measuring moisture without neutron source, instrument uses, stores all safer, nowadays strictly controlling under the overall situation of dangerous device, is easy to promote the use of.

Below in conjunction with accompanying drawing the utility model is described in further detail.

Description of drawings

Fig. 1 is the structural representation of the device storage configuration of the utility model synchro measure substrate medium density and moisture.

Fig. 2 is the structural representation of the device duty of the utility model synchro measure substrate medium density and moisture.

Fig. 3 a is the outside drawing of circular arc columnar water sub sensor, is applicable to Time Domain Reflectometry and frequency domain reflectometry and surveys moisture.

Fig. 3 b is the skeleton view of the sub sensor of circular arc columnar water shown in Fig. 3 a.

Fig. 4 a is the outside drawing of wire-wound columnar water sub sensor, is applicable to the time domain transmission method and surveys moisture.

Fig. 4 b is the skeleton view of the sub sensor of wire-wound columnar water shown in Fig. 4 a.

Fig. 5 is the schematic diagram that time domain reflectometry (TDR) is surveyed moisture.

Fig. 6 is the schematic diagram that time domain transmission method (TDT) is surveyed moisture.

Fig. 7 is the schematic diagram that frequency domain reflectometry (FDR) is surveyed moisture.

Fig. 8 a is the schematic diagram that time domain transmission-phase demodulation method (TDT-PD) is surveyed moisture.

Fig. 8 b is that the method for time domain transmission-phase demodulation shown in Fig. 8 a (TDT-PD) is surveyed key point oscillogram in the principle of moisture.

Fig. 9 is the schematic diagram that Time Domain Reflectometry-voltage to frequency transformation approach (TDR-F/V) is surveyed moisture.

Figure 10 is the schematic diagram of surveying moisture based on transmission line standing wave effect frequency domain reflectometry (FDR).

Among the figure, 1 γ-source chamber, 2 moisture transducers, 3 moisture transducer metering circuits, the sealing of 4PCB cabin, 5 lower springs, 6 slide bars, 7 upper springs, 8 cables, 9 location brake valves, 10 location brake valve triggers, 11 handles, 12 support bar top covers, 13 mobile jibs, 14 support bars, 15 pilot holes, 16 side channels, 17 side cabins, 18 radiation protection sheaths, 19 protection shutter storehouses, 20 radiation protection lead shields, 21 radiation protection trippers, 22 gamma-radiation detectors, 23 density slowdown monitoring circuits, 24 main circuit boards, 25 electric battery, 26 battery chargers, 27 display screens, 28 infrared receiving modules, the 29G module, 30 loam cakes, 31 bases.

Embodiment

As depicted in figs. 1 and 2, the device of the utility model synchro measure substrate medium density and moisture, comprise base 31 and main circuit board 24, one side of base 31 is provided with roughly vertical support bar 14 and source bar 13, γ-source chamber 1 is established in the lower end of source bar 13, the bottom of the opposite side of base 31 is provided with gamma-radiation detector 22, handle 11 1 ends of one approximate horizontal setting are fixedly connected with source bar 13, on the γ of described source bar 13-source chamber 1, be provided with successively moisture transducer 2 and PCB seal hatch 4, moisture transducer metering circuit 3 in moisture transducer 2 and the PCB seal hatch 4 is electrically connected, and moisture transducer metering circuit 3 is electrically connected with main circuit board 24.

As prior art, γ-source chamber 1 interior placement gamma-radiation source, it is moisture transducer metering circuit 3 that PCB seal hatch 4 is used for the sealing P.e.c., side cabin 17 is used for placing display screen 27, gamma-radiation detector 22, density measure circuit 23, main circuit board 24, electric battery 25, battery charger 26, control button 27, infrared receiving module 28, GPS module 29 etc., base 31 also has loam cake 30, also has radiation protection sheath 18, protection shutter storehouse 19, radiation protection lead shield 20, radiation protection tripper 21 in the base 31.

Support bar 14 is hollow among Fig. 1 and Fig. 2, the side of support bar 14 has vertical seam guide, and source bar 13 places in the support bar 14, and handle 11 1 ends are fixedly connected with source bar 13, the other end stretches out by the vertical seam guide of support bar 14, and can move up and down along this vertical seam guide.Source bar 13 places in the support bar 14, and as far as possible coaxial, makes apparatus structure simple, is easy to carry, uses and store.If source bar 13 is not interposing in the support bar 14, then whether hollow is unimportant for support bar 14, the structure shown in prior art CN201035151Y.Support bar 14 and source bar 13 are roughly vertical, and handle 11 approximate horizontal are owing to be easy to rely on handle 11 firmly lower potential source bars 13 in actual the use, make bar 13 lower ends in source go deep into the reason of substrate medium inside.

Because how in the open air this quasi-instrument working-yard uses, it is easy, the reliability particular importance.Moisture transducer 2 places in the source bar 13 jointly with moisture transducer metering circuit 3, has improved the reliability of moisture measurement, but simultaneously with the difficult that is connected of main circuit board 24.For guaranteeing that moisture transducer metering circuit 3 is connected with the reliable of main circuit board 24, moisture transducer metering circuit 3 forms with being electrically connected like this of main circuit board 24: be provided with slide bar 6 in the source bar 13 of hollow, slide bar 6 upper and lower end parts are subject to handle 11, can in the scope of both ends, slide up and down with respect to handle, 6 times termination lower springs 5 of slide bar, the lower end of lower spring 5 and PCB seal hatch 4 upper ends join, described slide bar 6 upper ends connect spring 7, the top cover 12 of termination support bar 14 on the upper spring 7, cable 8 is through described lower spring 5, slide bar 6 and upper spring 7, one end links to each other with moisture transducer metering circuit 3 through PCB seal hatch 4, and the other end links to each other with main circuit board 24 through top cover 12.

When device was in storage configuration such as Fig. 1,12 of the top covers of PCB seal hatch 4 upper ends and support bar 14 were close to; When the duty that is in such as Fig. 2,12 of the top covers of PCB seal hatch 4 upper ends and support bar 14 are distant.So the length of cable is constantly to change between the top cover 12 of PCB seal hatch 4 upper ends and support bar 14, and this variation is extremely frequently.Firm, reliable for what guarantee to be electrically connected, the utility model has adopted above-mentioned spring, sliding bar mechanism.Cable 8 partly curls up at upper spring 7 and lower spring 5, and the part that is positioned at slide bar 6 is relative fixing with slide bar 6.When handle 11 drives source bar 13 from topmost storage configuration position and moves downward, simultaneously also relatively slide bar 6 move downward from the upper end, until handle 11 moves to slide bar 6 lower ends, this process upper spring 7, slide bar 6 and lower spring 5 remain static always; Continue to move downward such as handle 11, because slide bar 6 lower ends are subject to handle 11, slide bar 6 will move downward with handle 11, and at this moment upper spring 7 stretches, lower spring 5 compressions.Curl up cable 8 on upper spring 7 and lower spring 5 also along with camber of spring, but can not injure cable 8.Until handle 11 moves to the lower limit of the vertical seam guide in support bar 14 sides, at this moment to enter substrate medium the darkest for source bar 13, records simultaneously innermost Media density and moisture.Handle 11 oppositely moves up, then before this lower spring 5 by the compressive state spread apart, at last to the extended state of spring 5, upper spring 7 is back to state of nature by extended state, to compressive state, at this moment handle 11 goes upward to the upper limit of the vertical seam guide in support bar 14 sides at last, and instrument is returned to storage configuration.By 21 effects of radiation protection tripper, the gamma-radiation source of source bar 13 lower ends is in the radiation protection lead shield 20.

This measurement device soil maximum degree of depth is 30 centimetres, tensile elongation for reasonable distribution upper spring 7 and lower spring 5, guarantee repeatedly to use still can keep favorable elasticity, sum up on the basis at great many of experiments and use experience, the length that draws slide bar 6 is 15～25 centimetres, be preferably 20 centimetres, upper spring 7 is 1:2～4 with the Length Ratio of lower spring 5 under state of nature, is preferably 1:3.

For fixing, take in support bar 14 top covers 12 to the cable between the base 31, the reliability that is electrically connected to improve device increases the service life, and is provided with the vertical side channel 16 that holds cable 8 in the outside of support bar 14.According to general knowledge, this side channel 16 is not positioned at vertical seam guide position, support bar 14 sides and gets final product.Preferably be positioned at position respect to one another.

Sidewall relative with vertical bar seam on support bar 14 has pilot hole 15, is provided with location brake valve 9 in the handle 11 and with the location brake valve trigger 10 of spring, location brake valve 9 can be under the effect of location brake valve trigger 10 with pilot hole 15 in conjunction with or separate.Pilot hole can be 5, lays respectively at that to make source bar 13 be in storage configuration, go deep into the substrate medium degree of depth be 0,10,20,30 centimetre position.This is because the conventional depth of this measurement device is 0,10,20,30 centimetre.If the standard of fathoming changes, certainly can take diverse location to establish pilot hole.

Moisture transducer 2 on the source bar 13 between γ-source chamber 1 and PCB seal hatch 4 can have different patterns according to different electromagnetic wave measurement principles.

For example, a kind of pattern shown in Fig. 3 a and Fig. 3 b, moisture transducer 2 for fixed by nonmetallic materials and mutually two cross sections of edge be the columnar component that circular-arc sheet metal forms.Wherein nonmetallic materials both were circular-arc sheet metal as fixing two cross sections, again as the medium that makes two sheet metal mutually insulateds, also as the middle filler of columnar component, to guarantee the intensity of bar, be applicable to take Time Domain Reflectometry (TDR) and frequency domain reflection (FDR) principle to measure moisture in the substrate medium.

Another kind of described moisture transducer 2 is wrapped on the nonmetal right cylinder for the U-shaped metal wire shown in Fig. 4 a and Fig. 4 b, is provided with ground wire, not conducting between ground wire and the U-shaped metal wire in the middle of the U-shaped metal wire.Be applicable to take time domain transmission (TDT) principle to measure moisture in the substrate medium.

The moisture transducer 2 of above-mentioned shape cooperates with source bar 13 switches dexterously, namely is convenient to go deep into measured medium, can fully contact with measured medium again, forms reasonably to measure electromagnetic field, guarantees measuring accuracy, and simple in structure, durable.

Adopt different moisture transducers 2,3 of moisture transducer metering circuits should match, and moisture transducer metering circuit 3 can adopt any circuit of prior art to realize.

About substrate medium density and the moisture computing method of non-neutron source, US Patent No. 8071937B2 and related data have detailed introduction, and the below only does concise and to the point citation explanation with regard to the utility model relevant portion.

Electromagnetic wave moisture measurement principle is based upon on Maxwell's classical electromagnetic theory, measurement be the velocity of propagation of electromagnetic wave in medium, utilize funtcional relationship between propagation velocity of electromagnetic wave and the medium specific inductive capacity to calculate the moisture number percent of volume of medium.Main by Time Domain Reflectometry (TDR, Time Domain Transmission is such as Fig. 5), time domain transmission (TDT, Time Domain Transmission is such as Fig. 6), or frequency domain reflection (FDR, Frequency Domain Reflectrometry is such as Fig. 7) realize.

Can derive the velocity of propagation v of electromagnetic wave in medium and the complex permittivity ε of medium=ε '-j ε from Maxwell's classical electromagnetic theory or experimental data " between exist

$v=\frac{c}{\sqrt{{\mathrm{\ϵ}}^{\′}\frac{1+\sqrt{1+{\tan }^2\mathrm{\δ}}}{2}}}---\left(4\right)$

In the formula: the velocity of propagation (m/s) of v electromagnetic wave in medium;

C electromagnetic wave velocity of propagation (m/s) in a vacuum;

The δ dielectric loss angle, tan δ=ε "/ε ';

The real part of ε ' complex permittivity is called specific inductive capacity usually for short;

ε " imaginary part of complex permittivity.

As ε '〉〉 ε " time, tan δ → 0, (4) formula is simplified to

$v=\frac{c}{\sqrt{{\mathrm{\ϵ}}^{\′}}}---\left(5\right)$

Can get from Fig. 5, Fig. 6

$v=\frac{L}{t}---\left(6\right)$

In the formula: the L electromagnetic wave is spread length (m) in waveguide;

The time that the t electromagnetic pulse is transmitted in waveguide (s).

Can be got by formula (5) (6)

$\sqrt{{\mathrm{\ϵ}}^{\′}}=\frac{t}{L}c---\left(7\right)$

Topp(1980), Whalley(1993) and White(1994) (Complex refractive index, its value equals to be reported in the complex refractive index of measured medium

) and the volume moisture of medium between (θ) have a simple linear relationship:

$\sqrt{{\mathrm{\ϵ}}^{\′}}=a_0+a_1\mathrm{\θ}---\left(8\right)$

For most non magnetic ore soil and artificial soil, formula (8) is (1MHz～10GHz) applicable in frequency range widely.The specific inductive capacity of water (ε ') under 20MHz, normal temperature (25 ℃), be about 80, and therefore the ε ' of soil media can think that the variation of ε ' is mainly determined by the moisture in the soil media under the same terms in 3～8 scopes.Be field planting for a specific time domain measurement sensor L, can converse specific inductive capacity by measuring t

And then extrapolate between the volume moisture of medium (θ).

There is several different methods can be used for measuring the transmission time t of electromagnetic wave in medium in the practical application of electromagnetic wave moisture measurement, all need the metal waveguide as induction element is implanted in the measured medium with open circuit or closed circuit mode, waveguide can be parallel lines or co-axial line form.

(1) TDR measures (Fig. 5).Electromagnetic waveguide as induction element is implanted measured medium with the open circuit form, measures square wave or step pulse and enters metal waveguide to the mistiming Δ t that receives reflection wave _TDR, and the time of electromagnetic pulse round trip transmission in waveguide;

(2) TDT measures (Fig. 6).Electromagnetic waveguide as induction element is implanted measured medium with closed circuit form, measures the time Δ t of electromagnetic pulse one way transmission in waveguide _TDT

(3) FDR measures (Fig. 7).Electromagnetic waveguide as induction element is implanted measured medium with the open circuit form, measures the standing wave voltage difference.

In TDR, the TDT metering system, directly measure square wave or step pulse mistiming Δ t _TDR, Δ t _TDTNeed complicated speed digital circuit and data to process, hardware cost is high.The utility model adopts two kinds of indirect modes to realize.Method one is the sine wave importing waveguide with a given frequency, determine Δ t by measuring sinusoidal wave phase shifts in waveguide, phase detecting circuit (PD, Phase Detector) by sensor internal converts phase shifts to electric signal (the common voltage signal V of being) output (such as Fig. 8 a and Fig. 8 b); Method two is that waveguide is incorporated into waveform concussion generator as time-delay element, frequency change by measured waveform concussion generator is determined Δ t, and frequency/voltage (F/V) change-over circuit by sensor internal converts frequency change to electric signal and exports (Fig. 9).For the time domain measurement sensor of a typing, can come calibration measurements V with the same soil of known different in moisture from low to high, set up and determine one to one funtcional relationship between V and the θ.

The FDR moisture measurement realizes that cost is low, but measuring principle is understood difficulty, is necessary to do a summary at this.FDR measures the propagation characteristic of electromagnetic wave in medium based on certain frequency, the electromagnetic wave when electromagnetic wave that transmits at metal waveguide moves into another medium by a kind of medium is because resistance difference can be in the surperficial generating portion reflection at two kinds of interfaces, produce standing wave with the incident wave stack, under incident wave condition (waveform, frequency, energy, output impedance) keeps constant situation, the variation of standing wave is only relevant with reflection wave, by the dielectric properties decision of the second material.The dielectric properties change of properties of supposing the second material is mainly changed by wherein moisture and determines that as long as medium satisfies isotropy, equally distributed condition, the mensuration of standing wave character can specifically be applied to the determination of moisture to water-bearing media.

Can describe more exactly the standing wave character of sensor with distributed parameter model and transmission line theory with the feature of medium complex permittivity variation, the equivalent electrical circuit of transmission line model as shown in figure 10.

Among Figure 10: E _gSignal generator output electromotive force;

Z ₀The signal generator internal resistance;

Z _pProbe impedance (being equal to loaded impedance herein);

The X probe length;

R _xDx, L _xDx, G _xDx and C _xThe distributed resistance of dx transmission line, distributed inductance, distribution electricity are led and distributed capacitance;

Z _xDx, Y _xThe distribution impedance of dx transmission line, distribution admittance;

Z _xTransmission line characteristic impedance.

Z _x＝R _x+jωL _x (9)

Y _x＝G _x+jωC _x (10)

According to impedance definition, characteristic impedance

$Z_c=\frac{\sqrt{R_x+\mathrm{j\ω}{L}_x}}{\sqrt{G_x+\mathrm{j\ω}{C}_x}}---\left(11\right)$

Equation for transmission line

$\left\{\begin{array}{c}d{U}_x=I_x{Z}_x\mathrm{dx}\\ {\mathrm{dI}}_x=U_x{Y}_x\mathrm{dx}\end{array}\right.---\left(12\right)$

Behind formula (12) second differential

$\left\{\begin{array}{c}\frac{d^2{U}_x}{{\mathrm{dx}}^2}-Z_x{Y}_x{U}_x=0\\ \frac{d^2{I}_x}{{\mathrm{dx}}^2}-Z_x{Y}_x{I}_x=0\end{array}\right.---\left(13\right)$

For solving equation (13), make γ ²=Z _xY _x, then

$\mathrm{\γ}=\sqrt{Z_x{Y}_x}=\sqrt{(R_x+\mathrm{j\ω}{L}_x)(G_x+\mathrm{j\ω}{C}_x)}=\mathrm{\α}+\mathrm{j\β}---\left(14\right)$

In the formula (14): the transmission coefficient of γ transmission line;

The α attenuation constant;

The β phase-shift constant.

Length of transmission line in this application is limited, can be used as one section loss-free line and processes α=0.Can get from the general solution of formula (13) and consideration formula (11) and (14)

$\left\{\begin{array}{c}{U}_x={\mathrm{Ae}}^{\mathrm{j\βx}}+{\mathrm{Be}}^{-\mathrm{j\βx}}\\ I_x=\frac{1}{Z_c}({\mathrm{Ae}}^{\mathrm{j\βx}}-{\mathrm{Be}}^{-\mathrm{j\βx}})\end{array}\right.---\left(15\right)$

Integration constant B can be determined by the boundary condition of a transmission line end points in the formula (15): U _x| _X=0=U _p, U _pBe the voltage at probe load two ends, after the substitution formula (15)

$\left\{\begin{array}{c}A=\frac{1}{2}(U_p+Z_c{I}_p)\\ B=\frac{1}{2}(U_p-Z_c{I}_p)\end{array}\right.---\left(16\right)$

$\frac{B}{A}=\frac{Z_p-Z_c}{Z_p+Z_c}=\mathrm{\ρ}---\left(17\right)$

ρ is defined as the reflection coefficient of transmission line.Formula (17) substitution formula (15) can be eliminated B,

U _x＝A(e ^jβx+ρe ^-jβx) (18)

Formula (18) is the complex expression of standing wave voltage on the transmission line, and integration constant A can be considered as the amplitude signal output of sinusoidal signal generator.

Standing wave voltage is measured respectively at two ends at transmission line in this application.Definition a point is in the x=0(probe tip), substitution formula (18)

U _a＝A(1+ρ) (19)

Definition b point comes from the transmission line junction at signal, and order

(implication refer to the length of transmission line get the sinusoidal signal wavelength 1/4), substitution formula (18)

U _b＝A(1-ρ) (20)

The standing wave voltage difference at a and b two ends is

U _ab＝U _a-U _b＝2Aρ (21)

The result of formula (19), (20) and (21) represent when the length of transmission line get input sinusoidal signal wavelength 1/4 the time, the crest of standing wave and antinode appear at the transmission line two ends simultaneously, the standing wave voltage difference maximum of output.

Standing-wave ratio (SWR) Г can represent with ρ in the transmission line theory

$\mathrm{\Γ}=\frac{1-\left|\mathrm{\ρ}\right|}{1+\left|\mathrm{\ρ}\right|}---\left(22\right)$

When the medium moisture changed, the impedance Z p of probe changed thereupon, and then caused reflection coefficient of transmission line ρ to change (formula 17).Standing-wave ratio (SWR) Г also simultaneously changes (formula 22) with ρ, so FDR determination of moisture method can be called the frequency domain reflection measuring method based on the standing-wave ratio (SWR) principle.

Claims (8)

1. the device of a synchro measure substrate medium density and moisture, comprise base (31) and main circuit board (24), one side of base (31) is provided with vertical support bar (14) and source bar (13), γ-source chamber (1) is established in the lower end of source bar (13), the bottom of the opposite side of base (31) is provided with gamma-radiation detector (22), it is characterized in that: a horizontally disposed handle (11) is connected with source bar (13), on the γ of described source bar (13)-source chamber (1), be provided with successively moisture transducer (2) and PCB seal hatch (4), moisture transducer metering circuit (3) in moisture transducer (2) and the PCB seal hatch (4) is electrically connected, and moisture transducer metering circuit (3) is electrically connected with main circuit board (24).

2. the device of synchro measure substrate medium density according to claim 1 and moisture, it is characterized in that: described support bar (14) is hollow, the side of support bar (14) has vertical seam guide, source bar (13) places in the support bar (14), handle (11) one ends are fixedly connected with source bar (13), the other end stretches out by the vertical seam guide of support bar (14), and can move up and down along this vertical seam guide.

3. the device of synchro measure substrate medium density according to claim 2 and moisture, it is characterized in that, described moisture transducer metering circuit (3) forms with being electrically connected like this of main circuit board (24): source bar (13) is hollow, be provided with slide bar (6) in the source bar (13) of described hollow, slide bar (6) upper and lower end parts is subject to handle (11), can in the scope of both ends, slide up and down with respect to handle, the lower termination lower spring (5) of described slide bar (6), the lower end of lower spring (5) and PCB seal hatch (4) upper end join, described slide bar (6) upper end connects spring (7), the top cover (12) of the upper termination support bar (14) of upper spring (7), cable (8) is through described lower spring (5), slide bar (6) and upper spring (7), one end links to each other with moisture transducer metering circuit (3) through PCB seal hatch (4), and the other end links to each other with main circuit board (24) through top cover (12).

4. the device of synchro measure substrate medium density according to claim 3 and moisture is characterized in that: be provided with the vertical side channel (16) that holds cable (8) in the outside of described support bar (14).

5. the device of synchro measure substrate medium density according to claim 3 and moisture, it is characterized in that: described upper spring (7) is 1:2～4 with the Length Ratio of lower spring (5) under state of nature, and the length of described slide bar (6) is 15～25 centimetres.

6. according to claim 2 to the device of one of 5 described synchro measure substrate medium density and moisture, it is characterized in that: have pilot hole (15) at the relative sidewall of the upper and vertical seam guide of described support bar (14), be provided with location brake valve (9) in the handle (11) and with the location brake valve trigger (10) of spring, location brake valve (9) can be under the effect of location brake valve trigger (10) with pilot hole (15) combination or separate.

7. the device of synchro measure substrate medium density according to claim 1 and moisture is characterized in that: described moisture transducer (2) is for being fixed by nonmetallic materials and two cross sections of mutually insulated are the columnar component that circular-arc sheet metal becomes.

8. the device of synchro measure substrate medium density according to claim 1 and moisture, it is characterized in that: described moisture transducer (2) is wrapped on the nonmetal right cylinder for the U-shaped metal wire, be provided with ground wire, not conducting between ground wire and the U-shaped metal wire in the middle of the U-shaped metal wire.

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