CN1023154C - Soil moisture measuring gauge with double-electrodes fixed in fields - Google Patents

Abstract

The present invention relates to an instrument for measuring the moisture content of soil in a positioning mode. The instrument is composed of electrodes and an electric connection detector for a soil electrode and a water electrode, wherein the electrodes comprise the soil electrode and the water electrode; the soil electrode is especially used for measuring the conductance of soil; the water electrode is especially used for measuring the conductance of soil water. The moisture content of the soil can be conveniently obtained by functional relationship between the moisture content of the soil and the conductance. The soil electrode and the water electrode are sensors for the conductance of the soil and the soil water. The detector is a device for detecting the conductance of substance and can adopt a manual or automatic or telemetering detection device.

Description

Soil moisture measuring gauge with double-electrodes fixed in fields

The present invention relates to a kind of surveying instrument of soil water content.

The surveying instrument of existing location survey soil water content mainly is tensiometer and Neutron Moisture instrument.It is very limited that tensiometer is used for potential energy, the measurement range of measured soil, and the potential energy of the holard and soil moisture content are two aspects of holard proterties in addition, are converted into water cut by potential energy and exist technical difficulty.Therefore the use of tensiometer is actually limited.The Neutron Moisture instrument directly is used for the measured soil water cut, and be not subjected to the restriction of measurement range, in the use, it is present a kind of method preferably, but the Neutron Moisture instrument has its intrinsic drawback, the instrument costliness, radiocontamination is arranged, and the difficulty of also exist proofreading and correct is again because it is the average moisture content of the spherical upper body of an about 50-80cm of diameter surveying, so reaction is insensitive aspect the variation on the observation soil water space-time, so its application also is very limited.In addition, in the forties, people just adopted the electrical measuring method measuring instrument, measuring principle is to imbed the absorption piece that a gypsum is made in soil, absorbs in the piece to insert two electrodes, after moisture in absorbing piece and the moisture in the soil reach balance, measuring the electricity that absorbs two electrodes in the piece leads, and conversing soil moisture content by typical curve, this apparatus measures result is subjected to Temperature Influence bigger, so measuring accuracy is very low.

The objective of the invention is to provide a kind of simple in structure, measuring accuracy height, field location survey soil water content measuring instrument easy to use.

The present invention is according to the ultimate principle of electrical measuring method, adopt bipolar electrode-native electrode to be connected with detecting device respectively with water power conductive electrode device, the soil electrode is the sensor of soil conductivity, the sensor that water power conductive electrode device is led as the soil water power, detecting device is for can detect the device that the material electricity is led, the electricity that the soil electrode is used in the measured soil is led, electricity in the water power conductive electrode measurement device holard is led, the electric conductivity value that water conductance electrode device is measured is proofreaied and correct the error of ion concentration and the caused measured soil moisture of temperature, and the funtcional relationship between being led by soil moisture content and electricity just can draw measurement result.Below in conjunction with accompanying drawing the present invention is explained in detail.

Fig. 1 water power conductive electrode apparatus structure;

Fig. 2 moisture transducer front view;

Fig. 3 moisture transducer vertical view;

Fig. 4 single-sensor rod-type bipolar electrode soil water measuring instrument;

Fig. 5 soil moisture probe front view;

Fig. 6 soil moisture probe vertical view;

Fig. 7 dual sensor rod-type bipolar electrode soil water measuring instrument;

The remote remote measurement soil water content of Fig. 8 system diagram.

Among the figure: 1-absorbent porous media, 2-silver platinum electrode, 3-substrate, 4-jointing compound, the 5-pad, the tap of 6-lead, 7-shell, 8,14,20-soil electrode, 9-substrate, 10,15,19-water power conductive electrode device, the 11-temperature sensor, 12, the 22-detecting device, 13-single-sensor bar, 16-moisture transducer, 17,26-soil, 18,23-lead-in wire, the 21-substrate, 24-soil moisture probe, 25-dual sensor bar, 26-pipe.

Soil electrode (8) adopts corrosion-resistant, and good conductivity has certain physical strength, and with bigger material of the affinity of soil such as carbon electrode etc., native electrode and soil contact portion be shaped as cylindrical or semisphere.Water power conductive electrode device (10) is made up of absorbent porous media (1), silver-colored platinum electrode (2), substrate (3), lead skewer head (6), shell (7).Absorbent porous media (1) adopts porous ceramics or porous high-absorbent materials such as sponge plastics or silica gel, the about 2mm of thickness.Vertically insert in the absorbent porous media (1) with corrosion-resistant, resistant to elevated temperatures two silver-colored platinum electrodes (2), the about 1mm of insertion depth, the spacing of two silver-colored platinum electrodes (2) is no more than 2mm.Absorbent porous media (1) is glued on substrate (3), substrate (3) adopts non-conductive, there are material such as organic glass of certain intensity to be used for fixing absorbent porous media (1), silver platinum electrode (2) is connected with line trap (6), adopt welding, connect by pad (5), absorbent porous media (1), substrate (3) is glued in a bowl-shape shell (7) by jointing compound (4).Soil electrode and water power conductive electrode device both can use separately, also can be according to the various combination of native electrode and water power conductive electrode device, and manufacture and be different soil water measuring instruments.Be that two native electrodes (8), a water power conductive electrode device (10) are fixed on the substrate (9) of a poor conductor material among Fig. 2, constitute a moisture transducer (16), substrate (9) is circular, be convenient to insert soil, there is the syndeton of screw thread or other form at the two ends up and down of annulus, the about 20mm of annulus external diameter is advisable, and a plurality of annular moisture transducers (16) connect and compose single-sensor bar (13), as being threaded by pipe (26).Moisture transducer (16), lead-in wire (18) draw from an end of pipe (26) with lead, with the upper and lower side sealing of each interface and single-sensor bar (13), a single entry rodmeter (13) and a cover detecting device (12) constitute a kind of single-sensor rod-type bipolar electrode soil water measuring instrument (Fig. 4) then.A native electrode (20) and a water power conductive electrode device (19) are fixed on the substrate (21) of a poor conductor material, constitute a soil moisture probe (24), two moisture probes (24) are one group and constitute a soil moisture sensor that these two moisture probes (24) place respectively on the position of two dual sensor bars (25) equal height.A plurality of moisture probes are contained on the diverse location of same non-conductive material pipe, are convenient to measure the water cut of different deep soils, the about 20mm of pipe external diameter, and the lead-in wire (23) of moisture probe (24) is drawn from the upper end of pipe, then will be sealed at both ends up and down.The pipe of two band soil moisture probes (24) constitutes dual sensor bar (25), and dual sensor bar (25) and detecting device (22) constitute dual sensor rod-type bipolar electrode soil water measuring instrument.

Detecting device (12,22) adopts different equipment according to different detection modes, and manual detection can adopt multimeter or conductivity meter (for example DOS-11A type conductivity meter), detects and write down employing XWD, XDD series display recorder automatically automatically.Remote remote measurement, its telemetry system is divided into field and indoor two large divisions, the field part comprises soil moisture sensor, signal converter, signal amplification and transmitter and signal monitoring pocket, indoor heating system comprises signal receiving processor, signal output apparatus and signal monitoring platform, and indoor heating system can be monitored a plurality of field system.

Using the present invention to carry out in the location survey of field, during single-sensor bar (13) or dual sensor bar (25) must vertically be placed into the soil, with drying and cross the aperture is that the native soil that 2mm sieves tamps, through after a while after (general experience big several times rainfall), probe fully contacts with soil, be that native electrode directly closely contacts with soil, the holard enters in the absorbent porous media of water power conductive electrode device, and instrument could normally use.For dual sensor bar (25), the distance during two measuring staffs are placed into the soil is about 400mm, and what measured is approximately the volume moisture content of the soil body that line with correspondence probe is the rotation ellipsoid of major axis.Similar to the result that the Neutron Moisture instrument measures, all be subjected to the influence of chad.Single-sensor formula soil water measuring instrument is measured is mainly the volume moisture content of soil very near around the probe, is subjected to the influence of chad very little.The former can be in order to study the acting in conjunction to moisture movement of grogs and chad, it is the reliable basis of estimation area moisture reserves, the latter can be in order to the independent action of research grogs to moisture movement, and sensitivity is than the former height, but its result can not be as the foundation of estimation area moisture reserves.Therefore, this dual mode can replenish mutually, can not replace mutually.Two cover single-sensor rod-type measuring instruments share can doublely do this two kinds of measurements, in actual the use, and shared cover detecting device, the lowering apparatus cost greatly of a plurality of single-sensor bars (13).

Among Fig. 3, a temperature-sensing element (11) is set in the moisture transducer (16), the present invention's measured soil water cut simultaneously then, the space-time dynamic of soil salt, the soil moisture changes.

When using the present invention to carry out the soil water content location survey, need only electric conductivity value, just can ask and calculate soil moisture content by must be unearthed in the detecting device (12,22) interelectrode electric conductivity value and water power conductive electrode device.Below introduce in detail the method for using the present invention to obtain soil moisture content.

Being provided with a volume is the moistening soil body of Vs, wherein the shared volume V of water _W, conductive ion soluble in water has the X gram equivalent, with water during as solvent, its N be μ=X/Vw soil body as " during solvent ", N is μ s=X/Vs, then the volume moisture content of soil:

θ＝ (Vw)/(Vs) ＝ (μs)/(μw) （1）

Following formula shows if obtain the conductive ion concentration μ s of soil and the conductive ion concentration μ w in the holard simultaneously, just can obtain water cut θ, in order to realize this goal, adopt two arrays of electrodes: native electrode and water power conductive electrode device are measured the electricity that the electricity in the soil leads in the Gs and the holard respectively and are led Gw, because there are certain functional relation in the conductive ion concentration of material and electricity between leading, therefore lead the water cut that just can draw soil according to electricity.Because the water cut of soil is only relevant with the ratio of conductive ion concentration in the conductive ion concentration of soil and the holard, has so just eliminated the interference of ion concentration and temperature.

Be located at standard temperature T _ODetermined funtcional relationship respectively by experiment:

μs（T ₀）＝f ₁｜Gs（T ₀）｜ （2）

μw（T ₀）＝f ₂｜Gw（T ₀）｜ （3）

Gs(T wherein ₀), Gw(T ₀) be respectively at T ₀The electricity that time soil electrode and water power conductive electrode device measure is led.Be located at non-standard temperature T=T again ₀+ △ T, native electrode and water power conductive electrode device record electricity lead be respectively Gs(T), Gw(T), then in certain precision, the water cut of soil is

θ＝ (f ₁｜G _s(T)｜)/(f ₂｜G _w(T)｜) （4）

(4) meaning of formula is: if in a certain temperature T ₀Determined soil conductivity Gs(T ₀) and soil conductive ion concentration μ s(T ₀) funtcional relationship f ₁| Gs(T ₀) | and the electricity of the holard is led Gw(T ₀) with the conductive ion concentration μ m(T of the holard ₀) funtcional relationship f ₂| Gw(T ₀) |, f then ₁, f ₂Still can determine Gs(T in other temperature T), Gw(T) with conductive ion concentration concern f ₁| Gs(T) |, f ₂Though | Gw(T) | f ₁| Gs(T) |, f ₂| Gw(T) | might not equal real conductive ion concentration in the solution, but ratio f ₁| Gs(T) |/f ₂| Gw(T) | in given accuracy, provided soil moisture content.

Can prove the caused relative error of (4) formula in theory:

Re≤（0.02△T） ²（5）

Can deduce out a radius from (1) formula in theory and test formula:

$\mathrm{\theta =}\frac{\frac{1}{k_s}{C}_s{\mathrm{(T)-\sigma so(T}}_o{\mathrm{,\theta }}_o{\mathrm{)(1-\alpha \theta }}_o)}{\frac{G_w{\mathrm{(T)-G}}_{\mathrm{ow}}\mathrm{(To)}}{\mathrm{km}}{\mathrm{+\alpha \sigma so(To,\theta }}_o)}$

Its theoretical relative error

Re＜△T·｜Wax（△s，△w）｜

$\mathrm{\Delta s=}\frac{{\mathrm{\alpha \sigma so(T}}_o{\mathrm{,\theta }}_o)}{\frac{1}{\mathrm{ks}}{\mathrm{Gs(T)-\sigma so(To,\theta }}_o{\mathrm{)(1-\alpha \theta }}_o)}$

(6), in (7) two formulas

Soil moisture when T-measures

Gs(T)-electricity that temperature T time soil electrode is measured leads

Gw(T)-water power conductive electrode device is measured during temperature T electricity leads

Gow(T ₀)-temperature T ₀Shi Shuidian conductive electrode device is to electric conductivity value that pure water measured

Ks-soil electrode instrument constant

Kw-water power conductive electrode device instrument constant

A-water cut coefficient

α-temperature coefficient

T ₀-standard temperature

θ ₀-soil annual water cut (or standard water-content)

σ so(T ₀, θ ₀)-at T ₀, θ ₀The time the apparent conductivity T in solid phase of soil surface be the amount that need not measure, Gs(T), Gw(T) measure by native electrode and water electrode respectively, other parameters are by measuring.

Parameter K s, Kw can determine with the following method:

1.ks determine

Can prove in theory

$\mathrm{ks=2\pi r\; ［1＋}\frac{\mathrm{<figure-callout\; id="20"\; label="r"\; filenames="891058354\_DRIMG2.png"\; state="\{\{state\}\}">r</figure-callout>}}{\mathrm{20}}+\frac{(\frac{r}{\mathrm{20}})}{\mathrm{1-(}\frac{r}{\mathrm{20}})}\mathrm{+\dots \dots ］}$

Wherein γ is the equivalent redius of native electrode, and 0 is two native distance between electrodes, if γ＜D, then

Ks≈2πγ （9）

Be approximately constant, (8) formula is suitable for not leaning on down basement rock, the BC soil of near up and down table soil, and for nearly basement rock or the nearly measurement of showing soil, its Ks should be determined by experiment.Get the container of a length and width Gao Jun greater than 2D, fill the solution that known conductivity is σ w (as tap water) in it, two native electrodes are vertically put into solution from container, two electrodes are on the same horizontal level all the time, and the electrode relative position is identical with the electrode relative position of field experiment, measure the distance h (comprising distance) and the two interelectrode electricity on the dried up plane of electrode and lead Gs(h from container bottom), by formula

Ks（h）＝ (Gs（h）)/(σw) （10）

Determine Ks(h).Experiment will show that obvious variation Ks(h) is only just arranged near the water surface or bottom the time.

Embodiment 1:

Conductivity w=1.134 * 10 of known water (tap water) ^-2Europe ^-1Rice ^-1, the distance of the water surface at the bottom of the pond is 1 meter, native electrode radius γ=2mm, and two native electrode separation D=0.4 rice, then theoretical Ks ≈ 2 π γ=0.01257(m), and corresponding different depth of water measured results, utilization formula (10) draws table 1.(table 1 is seen the literary composition back)

2, determining of Kw:

Formula below utilizing:

Kw= (Gw(T)-Gow(T _O))/(σw(T)) （11）

Water power conductive electrode device is immersed in the solution of known conductivity σ w and measures Gw(T after two hours), Kw.

Embodiment 2:

Known water conductivity w=1.134 * 10 ^-2Ω ^-1M ^-1, record Gw=0.1324 * 10 ^-3Ω ^-1, Gow=0.0411 * 10 ^-3Ω ^-1, the instrument constant of water power conductive electrode device then,

Kw＝ (Gw-Gow)/(σw) ＝0.00805m

Parameter a, α, T ₀, θ ₀, σ so(T ₀, θ ₀) method of determining is as follows:

Get one at sample plot and squarely be that L(is long) * W(is wide) * the H(height) the soil body, size is advisable after being fit to weight method measured soil water cut and a water electrode being installed the influence of soil structures can be ignored.With soil body former state pack into one with volume and nonmetal, do not absorb water, have certain intensity, in the standard vessel that lightweight material (as organic glass) is manufactured, the wallboard at vessel length direction two ends respectively equals can sliding in the longitudinal direction of W * H for area, be easy to be fixed on metallic conduction plate (as native electrode) again, water power conductive electrode device is installed in the vessel sidewall middle part, and insert simultaneously in the soil body with packing into of soil body sample, fully contact with soil with the adsorption plane of water electrode and be advisable.Add suitable quantity of water (soil body reaches field capacity and gets final product), and whole vessel are put into constant temperature oven with the control temperature variation, generally with annual room temperature T ₀Change is advisable up and down, stablizes after 2 hours and just can measure.Temperature T, the water power conductive electrode device electricity that can measure the soil body are respectively led Gw(T), native electrode conductance Gs(T), and record volumetric water content of soil θ with weight method, calculate by following formula again:

σ ss(T. θ) be the apparent conductivity in solid phase of soil surface when temperature T and water cut θ, so obtain first array (σ ss. θ ₁.T ₁).Change temperature T, after two hours, repeat above-mentioned measurement, get second array (σ ss2, θ ₂, T ₂) ..., up to obtaining n array

（σssi、θi、Ti）i＝1、2、……n （13）

To these several arrays carry out binary linear regression analyze a matched curve σ ss(T. θ)=σ so(T ₀. θ ₀) [1+a(θ-θ ₀)+α (T-T ₀] (14)

Obtained each parameter respectively by matched curve (14).

Embodiment 3:

The a certain soil body has been carried out 20 times according to the method described above measured, recorded T, θ, Gw, Gs respectively, and calculate σ ss, wherein L * w * H=0.1 * 0.06 * 0.06(m by formula (14) ³), km=0.01530(w) data of surveying are provided by table 2, get equation through binary linear regression

σss＝b ₀+b ₁T+b ₂θ （＊）

B wherein ₀=-3.3 * 10 ^-5, b ₁=1.09 * 10 ^-6, b ₂=1.10 * 10 ^-4, (*) coefficient of multiple correlation R of formula=0.989, residue standard error S=1.02 * 10 ^-6The established standards temperature T ₀=20 ℃, average soil moisture θ ₀=0.26, substitution (*) formula gets

σso＝σss（T ₀，θ ₀）＝1.74×10 ^-5（Ω ^-1·w ^-1）

(*) formula and (14) formula are relatively got:

A σ so=b ₂Promptly=(σ so)/(b ₂)=6.33

α σ so=b ₁Be α=(σ _So)/(b ₁)=6.27 * 10 ^-2(k-1)

With a, α, σ so, θ ₀, T ₀Radius during substitution (6) formula just obtains surveying is tested formula.

After having determined above-mentioned constant, just meter is calculated the water cut of soil easily.As instrument being used for the field one-point measurement, the single-sensor bar (13) that has three annular moisture transducers (16) is inserted in the soil, the degree of depth h of three moisture transducers (16) in soil is 0.3,0.5,0.7 meter, respectively native electrode and water power conductive electrode device are measured with conductivity meter detecting device (12), measure the electric conductivity value of water power conductive electrode device and native electrode, then by (6) formula calculate the average moisture content of every layer of soil, each parameter is got top measured value, and measurement result is as follows.(table a sees the literary composition back)

Measure and calculate water cut, can also obtain by the concrete functional form of determining (2), (3) two formulas earlier by (4) formula.

Because ratio μ s/ μ w can be understood as the ion concentration of soil with respect to the holard in (1) formula, perhaps further be interpreted as the concentration and the ratio of the holard of a certain relatively standard solution of soil with respect to the concentration of same standard solution, therefore, only need to determine the relative concentration value of the soil and the holard, and need not determine the absolute value of their concentration, this determines function f for experiment ₁And f ₂Brought great dirigibility.For example, it is contemplated that a kind of ideal soil (or solution), its conductive ion concentration μ ₀Lead G with its electricity ₀Funtcional relationship is arranged:

μ ₀＝f ₀（G ₀） （15）

This relation is temperature independent.So can under constant room temperature, demarcate (2), (3) formula by experiment with (15) formula.This be because:

θ= (f ₁(Gs))/(f ₂(G _w)) = (f ₁(G _s))/(f _o(G _o)) · (f _p(G _o))/(f ₂(G _m)) = (f ₁(G _s))/(f _o(G _o)) / (f ₂(G _w))/(f _o(G _o)) （16）

Promptly the relative concentration of two kinds of solution equals their ratios of the relative concentration of another kind of relatively solution respectively.

Further, we in addition can stipulate that any same form in (2), (3) formula obeys certain simple proportional relation, tie up to the pass of this regulation then and be determined by experiment another formula under the constant room temperature, this has just simplified experimental arrangement greatly.This is because can change the form of (16) formula, makes to demarcate a certain formula f under experiment condition ₁Or f ₂Has simple proportional relation.

(2), the laboratory of (3) formula is demarcated and is promptly determined its concrete form from the laboratory simply.

The sample mode of soil, instrument and operating process remove maintenance one steady temperature T ₀Outward, with definite parameter a, α, σ so(T ₀, θ ₀) method in the institute be described finish identical.Here establish and measured a column data group by above-mentioned experiment:

｜θi，Gssi（T ₀），Gwi（T ₀）｜i＝1、2、……n （17）

Gssi(T wherein ₀), Gwi(T ₀) be respectively the native electrode of standard vessel and water power conductive electrode device in temperature T ₀The i group electricity that measures is led, and θ i is corresponding water cut.

The first step: regulation f ₁Or f ₂Functional form:

For the sake of simplicity, regulation

μw（T ₀）＝GwGw（T ₀） （18）

Gw is the coefficient that balance both sides unit is provided with, Gw=1 on the numerical value.So corresponding each Gwi(T ₀), there is one

μmi（T ₀）＝GwGwi（T ₀） （19）

In second step, determine soil conductive ion concentration

Get by (1) formula

μs＝θμw

Corresponding each to θ i and Gwi(T ₀) there is one

μsi（T ₀）＝GwθiGwi（T ₀） （20）

The 3rd step was determined the equivalent conductance that native electrode measures in the field experiment.

Because the native electrode of standard vessel and the native electrode of field experiment are all inequality in shape and position, so Gssi(T ₀) can not represent the equivalent conductance Gsi(T of field experiment ₀), but have a fixing transformational relation between them,

Gsi（To）＝ (LK2)/(WH) Gssi（To） （21）

Wherein Ks is determined by preceding method.

The 4th step was set up soil conductivity Gs(T ₀) and soil conductive ion concentration μ s(T ₀) concern f ₁| Gs(T ₀) |

Obtain row and the corresponding array of array (17) by (20), (21) two formulas:

｜μsi（T ₀），Gsi（T ₀）｜i＝1、2……，n （22）

Use this columns group again, obtain experimental formula by regretional analysis

μs＝f ₁｜Gs（T ₀）｜ （23）

Through above-mentioned four steps, just obtained the bipolar electrode electrical measuring method and be used for the experimental formula that the field is measured:

θ= (f ₁｜G _s(T)｜)/(GwGw(T)) （24）

If f ₂(Gw) simplification may cause the fitting degree of (24) formula not high, at this moment can adopt interior among a small circle linear fitting:

Suppose in the field and record Gw(T) and Gs(T), Gs(T) drop on Gsi(T ₀) and Gsi+1(T ₀) between, wait the μ s(T that sues for peace) must drop on corresponding μ si(T ₀) and μ si+1(T ₀) between,

And be similar to and satisfy linear relationship:

(G _si+1(To)-G _s(T))/(μsi+1(To)-μs(T)) = (G _s(T)-G _si(To))/(μs(T)-μsi(T _G)) （25）

Solve thus:

μs（T）＝ 1/(1+R) ｜μsi+1（T ₀）+Rμsi（To）｜ （26）

Wherein:

R＝ (Gsi+1（To）-Gs（T）)/(Gs（T）-Gsi（To）) （27）

Soil moisture content

θ＝ (μs（T）)/(CwGw（T）) （28）

Embodiment 4

T=25 ℃ the soil body among the embodiment 3 having been carried out 20 times in a steady temperature (as room temperature) measures, obtain θ, Gss, Gw respectively, and by (20) formula calculate μ s, by (21) formula calculate Gs, all data are provided by table 3, Ks=0.01257(w), L * W * H=0.1 * 0.06 * 0.06(w ³).Can obtain the funtcional relationship of various ways by simple regression analysis:

1、μs＝a+bGs

Wherein: a=1.06 * 10 ^-6B=1.20

Coefficient R=1 residual mean square difference S=3.9 * 10 ^-8

2、μS＝a+b ₁gGs

Wherein: a=0.164 b=0.084

R＝0.996 S＝6.89×10 ^-4

- (b)/(G ₂)

3、μs＝ae

Wherein: a=0.098 b=0.092

R＝0.99999 S＝7.22×10 ^-4

4、μs＝aG ^b _s

Wherein: a=1.2 b=1.000

R＝1 S＝2.08×10 ^-8

5、μs＝ 1/(a+be-G _s)

Wherein: a=-891 b=948

R＝1 S＝1.66×10 ^-3

6、μs＝ $\sqrt{\mathrm{a+bGs+CGs}}$

Wherein: a=1.1 * 10 ^-7B=1.05 * 10 ^-5C=1.45

R＝1 S＝4.8×10 ^-8

7、μs＝ (Gs)/(a+bGs+CGs)

Wherein: a=0.83 b=8.13 * 10 ^-4C=-6.32 * 10 ^-4

R＝1 S＝7.1×10 ^-9

8、μs＝a+ (b)/(Gs) + (C)/(Gs)

Wherein: a=0.108 b=-3.18 * 10 ^-3C=3.02 * 10 ^-5

R＝0.9995 S＝2.5×10 ^-4

According to the fitting degree of the big or small discriminant function of residual mean square difference S, wherein best with the 7th kind of situation, if adopt this functional form, then the used experimental formula (24) of field experiment is:

θ＝ (Gs)/(Gw) 1/(a+bGs+CGs) （29）

Wherein: a=0.83 b=8.13 * 10 ^-4C=-6.32 * 10 ^-4

If carry out the field one-point measurement with dual sensor rod-type bipolar electrode soil water measuring instrument, three pairs of soil moisture probes (24) are set on two dual sensor bars (25), corresponding locational two probes on three moisture probes on each bar, two bars constitute moisture transducers.Dual sensor bar (25) inserts in the soil, three couples of soil moisture probe (24) degree of depth h in soil layer are respectively 0.3,0.5,0.7 meter, successively each is measured probe with conductivity meter detecting device (22), record the electric conductivity value of water power conductive electrode device and native electrode everywhere respectively, calculate to such an extent that corresponding soil and average moisture content are as follows by (29) formula then.(table b sees the literary composition back)

In sum, the present invention is as the instrument of field location survey soil water content, sensing element is being placed into the soil, after having determined every constant of instrument, just can measure soil water content by measuring electric conductivity value easily, and can practicable as required manual measurement, measurement and remote remote measurement automatically.Reach in the temperature difference under 20 ℃ the condition, the present invention and weight method have been done control experiment, both deviations drop in the instrument error scope less than 3%.The present invention compares with the Neutron Moisture instrument, has sensitivity and accuracy is higher, pollution-free, (conductivity meter detects cost and is about 1/5000 of Neutron Moisture instrument low price, self-recording device is about 1/50, remote measurement is about 1/40), advantages such as fitting operation is easier, and measuring speed is faster, so the present invention will improve the present situation to monitoring soil moisture greatly, make the moisture distribution of automatic monitoring large watershed integral body and dynamically become possibility, to instructing agricultural irrigation, the resource that taps ground water resources prevents erosion, in conjunction with meteorological observation, set up nearly mid-term drought and flood forecasting system and have extremely important meaning.

Table 1:

h（m） 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Gs（10 ^-3·Ω ^-1） 0.079 0.116 0.134 0.140 0.141 0.141 0.141 0.140 0.136 0.119 0.081

Ks（10 ^-3m） 7.0 10.3 11.9 12.4 12.5 12.5 12.5 12.4 12.0 10.5 7.2

Table a:

H(rice) Gs(10 ^-3Ω ^-1) Gw(10 ^-3Ω ^-1) θ

0.3 0.02120 0.1134 0.370

0.5 0.01864 0.1146 0.320

0.7 0.02100 0.1167 0.350

Table b:

H(rice) Gs(10 ^-3Ω ^-1) Gw(10 ^-3Ω ^-1) θ (%)

0.3 0.1255 0.0346 33.2

0.5 0.1290 0.0373 34.8

0.7 0.1344 0.0427 38.3

Table 2

Sequence number T(℃) θ Gw(10 ^-3Ω ^-1) Gs(10 ^-3σ ss(10 ^-3Ω ^-1R ^-1)

1 18.4 0.393 0.114 0.107 0.028

2 20.5 0.378 0.119 0.107 0.03

3 23 0.365 0.124 0.108 0.031

4 25.6 0.358 0.131 0.111 0.034

5 27.8 0.352 0.135 0.113 0.036

6 30.5 0.344 0.14 0.115 0.038

7 33.4 0.334 0.147 0.117 0.041

8 36.7 0.332 0.155 0.122 0.045

9 39.2 0.32 0.159 0.121 0.046

10 17 0.315 0.112 0.084 0.022

11 20 0.308 0.117 0.085 0.024

12 23 0.302 0.124 0.089 0.026

13 24 0.291 0.127 0.088 0.026

14 26.6 0.282 0.133 0.089 0.028

15 28.2 0.274 0.136 0.089 0.028

16 30 0.264 0.139 0.088 0.029

17 32.1 0.256 0.143 0.087 0.03

18 33.2 0.24 0.147 0.084 0.029

19 35.3 0.232 0.15 0.083 0.03

20 37.6 0.224 0.156 0.083 0.031

Table 3

Sequence number θ Gss(10 ^-3Ω ^-1) Gw(10 ^-3Ω ^-1) μ s Gs(10 ^-3Ω ^-1)

1 0.393 0.119 0.127 0.05 0.0415

2 0.378 0.1144 0.127 0.0481 0.0399

3 0.365 0.1101 0.127 0.0463 0.0384

4 0.358 0.1089 0.128 0.0458 0.038

5 0.352 0.1064 0.127 0.0447 0.0372

6 0.344 0.1031 0.126 0.0433 0.036

7 0.332 0.0999 0.127 0.042 0.0349

8 0.32 0.0967 0.127 0.0406 0.0338

9 0.315 0.0944 0.126 0.0397 0.033

10 0.308 0.0936 0.128 0.0393 0.0327

11 0.291 0.0873 0.126 0.0367 0.0305

12 0.282 0.0848 0.126 0.0356 0.0296

13 0.274 0.0823 0.126 0.0346 0.0287

14 0.264 0.0802 0.128 0.0337 0.028

15 0.256 0.0773 0.127 0.0325 0.027

16 0.241 0.0726 0.127 0.0305 0.0254

17 0.232 0.0694 0.126 0.0292 0.0242

18 0.224 0.0679 0.128 0.0286 0.0237

19 0.21 0.0628 0.126 0.0264 0.0219

20 0.203 0.0611 0.127 0.0257 0.0213

Claims (8)

1, a kind of soil water measuring instrument, comprise the native electrode of franchise mensuration soil conductivity and the detecting device that is electrically connected with native electrode, it is characterized in that this surveying instrument also comprises the water power conductive electrode device that the electricity of water in the franchise measured soil is led, water power conductive electrode device also is electrically connected with detecting device, described native electrode adopts corrosion-resistant, and the material bigger with the affinity of soil, described water power conductive electrode device is by absorbent porous media, the silver platinum electrode, base stage, line trap, shell is formed, the soil electrode is used as the sensor that the measured soil electricity is led, the water power conductive electrode is used as measures the sensor that the soil water power is led, the electric conductivity value that water conductance electrode device is measured is proofreaied and correct the error of ion concentration and the caused soil water content of temperature, calculate measurement result by the funtcional relationship between soil moisture content and electric leading, the device that detecting device is led for energy detection material electricity.

2, soil water measuring instrument according to claim 1 is characterized in that absorbent porous media adopts porous ceramics or porous high-absorbent materials such as sponge plastics or silica gel.

3,, it is characterized in that two native electrodes and water power conductive electrode device are fixed on the substrate of a poor conductor material and constitute a moisture transducer according to the described soil water measuring instrument in one of claim 1 or 2.

4, soil water measuring instrument according to claim 3, the substrate that it is characterized in that the poor conductor material is circular, and there is screw connection structure at two ends up and down, and the alternate connection of a plurality of annular moisture transducers constitutes the single-sensor bar.

5, according to the described soil water measuring instrument in one of claim 1 or 2, it is characterized in that a native electrode and water power conductive electrode device are fixed on the substrate of a poor conductor material constitutes a soil moisture probe, two soil moisture probes are one group and constitute a soil moisture sensor, these two probes are placed on the position of equal height of two dual sensor bars, a plurality of soil moisture probes are contained on the diverse location of same non-conductive material pipe, the soil moisture probe lead wire is drawn from an end of pipe, the upper and lower side sealing of pipe, the pipe of two band soil moisture probes constitutes the dual sensor bar.

6, soil water measuring instrument according to claim 1 is characterized in that detecting device adopts multimeter or conductivity meter.

7, soil water measuring instrument according to claim 1 is characterized in that detecting device adopts detection and pen recorder automatically.

8, soil water measuring instrument according to claim 1 is characterized in that detecting device adopts remote telemetering device.

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