CN106324048A - Soil humidity sensor based on oscillation circuit and working method of soil humidity sensor - Google Patents

Abstract

The invention relates to the field of geology detection equipment and discloses a soil humidity sensor based on an oscillation circuit and a working method of the soil humidity sensor. Two electrode plates and soil located between the two electrode plates are taken as a capacitor, a dielectric constant of the soil can be obtained through backstepping based on the obtained frequency value of the oscillation circuit by the use of the relation between the frequency and the capacitance of the oscillation circuit and the relation between the capacitance and the dielectric constant, the humidity value of the soil is further obtained, accordingly, the defect of low linearity of transmission FDR and TDR can be overcome, the soil moisture can be rapidly, accurately and stably measured. Besides, the soil humidity sensor further has the characteristics that the circuit structure is simple, the cost is low, the application is convenient and the like, is high in practicability and facilitates actual popularization and use.

Description

A kind of soil humidity sensor based on oscillation circuit and method of work thereof

Technical field

The present invention relates to ground quality detection apparatus field, in particular it relates to a kind of soil moisture based on oscillation circuit sensing Device and method of work thereof.

Background technology

Existing soil moisture content measuring method with TDR (Time-Domain Reflectometry, time domain reflection technology) and FDR (Frequency-Domain Reflectometer, frequency domain reflection technology) is main.Wherein, the operation principle of TDR technology is Utilize the electromagnetic wave different characteristic of transfer rate in the medium of differing dielectric constant, by accurately measuring electromagnetic wave from transmitting terminal To the time difference of receiving terminal, thus obtain electromagnetic wave transfer rate in soil, thus anti-dielectric constant of releasing, and and then To volumetric water content of soil (i.e. humidity value).And FDR technology is to utilize electromagnetic pulse principle, propagate in media as well according to electromagnetic wave Frequency measures the apparent dielectric constant of soil, and and then obtains volumetric water content of soil.

Although existing FDR and TDR technology is effective, but all have that the linearity is low, precision is easily by such environmental effects, electricity Road is complicated, equipment costly with the problem such as in-site installation flow process is complicated, the suitability is limited.

Summary of the invention

For aforementioned problem of the prior art, the invention provides a kind of soil humidity sensor based on oscillation circuit and Its method of work, two battery lead plates and the soil that is between two battery lead plates are considered as the parallel plate capacitor of a capacitance to be measured by it Device, is then utilized oscillation circuit frequency and the relation of capacitance and capacitance and the relation of dielectric constant, is vibrated by acquisition The frequency values in loop, can be back-calculated to obtain the dielectric constant of soil, and then obtains the humidity value of soil, so can get rid of tradition The defect that in FDR and TDR method, the linearity is the highest, it is possible to quickly realize quick, the accurate and stable measurement of soil moisture.This Outward, described soil humidity sensor also has that circuit structure is simple, with low cost and the feature such as application is convenient, practical, just Promote in reality and use.

The technical solution used in the present invention, on the one hand provides a kind of soil humidity sensor based on oscillation circuit, bag Including plane-parallel capacitor, inductance, oscillation module, counting module and processing module, wherein, described plane-parallel capacitor includes two electricity Pole plate and the fixing insulating part connecting two battery lead plates, make two battery lead plates be parallel to each other simultaneously, and respectively as described parallel-plate electricity The two poles of the earth of container；The two poles of the earth of described plane-parallel capacitor constitute an oscillation circuit with described inductance in parallel, and make described vibration Loop is sequentially connected in series described oscillation module, described counting module and described processing module.

Optimize, described oscillation module include voltage controlled oscillator amplifier that model is MC100EL1648D, the first electric capacity, 8th electric capacity, the 9th electric capacity, the first resistance and the 3rd resistance；8th pin of described voltage controlled oscillator amplifier connects described the One end of three resistance, in parallel described between the other end of described 3rd resistance and the first pin of described voltage controlled oscillator amplifier Oscillation circuit；Second pin of described voltage controlled oscillator amplifier and the 3rd pin are connected, and connect the described of ground connection the most respectively 8th electric capacity and described 9th electric capacity of ground connection；5th pin of described voltage controlled oscillator amplifier and the 7th pin are connected, so Rear described first electric capacity connecting ground connection, is sequentially connected in series described first resistance and DC source simultaneously；Described voltage controlled oscillator is put 6th pin ground connection of big device, the 4th pin of described voltage controlled oscillator amplifier is as the outfan of described oscillation module.

Optimize, 12 grade of two mechanism ripple counter that described counting module includes that model is MC74HC4040AD, the 4th Resistance and the 7th resistance；Tenth pin of described 12 grade of two mechanism ripple counter as the input of described counting module, and Connect one end and one end of described 7th resistance of described 4th resistance, the other end of described 4th resistance and described 12 grades respectively 16th pin of two mechanism ripple counters connects DC source, the other end ground connection of described 7th resistance respectively；Described 12 8th pin ground connection of level two mechanism ripple counter, the 11st pin of described 12 grade of two mechanism ripple counter connects described The control output end of processing module, 12 output pins of described 12 grade of two mechanism ripple counter are as described counting module Outfan.

Optimizing, described processing module includes singlechip chip that model is STM8L151C8T6-48, the 3rd electric capacity and the Five resistance；Second pin of described singlechip chip is as the control output end of described processing module, and connects described respectively One end of three electric capacity and one end of described 5th resistance, the other end of described 5th resistance connects DC source, described 3rd electricity The other end ground connection held.

Optimize, between described oscillation module and described counting module, be in series with pre-frequency division module.Optimize further, It is in series with between described oscillation module and described pre-frequency division module or between described pre-frequency division module and described counting module Capacitance.Described pre-frequency division module uses model to be the pre-distributor of MC12080D.

Optimizing, the outer surface of described battery lead plate is provided with zinc coat.

The technical solution used in the present invention, on the other hand provides a kind of aforementioned soil moisture based on oscillation circuit sensing The method of work of device, comprises the steps: that plane-parallel capacitor is inserted in soil to be measured by S101.；S102. oscillation mode is started Block, encourages oscillation circuit, produces oscillator signal；S103. described oscillator signal is imported counting module, pass through count module The counting of block, obtains frequency measurement f of described oscillator signal；S104. described frequency measurement f of processing module acquisition, and from The local battery lead plate area S reading plane-parallel capacitor and plate spacing d, then according to equation below calculates Jie of soil to be measured Electric constant ε:

$\mathrm{\ϵ}=\frac{d}{{\mathrm{\ϵ}}_{0}SL{\left(2\mathrm{\π}f\right)}^2}$

In formula, ε₀For permittivity of vacuum, L is the inductance value of inductance in oscillation circuit；S105. calculate to be measured according to equation below The humidity value of soil

Then described humidity value is exported

Optimize, when being in series with pre-frequency division module between described oscillation module and described counting module, then according to such as Lower formula is according to the DIELECTRIC CONSTANT ε of equation below calculating soil to be measured:

$\mathrm{\ϵ}=\frac{d}{{\mathrm{\ϵ}}_{0}SL{\left(2\mathrm{\π}\mathrm{\λ}f\right)}^2}$

In formula, ε₀For permittivity of vacuum, L is the inductance value of inductance in oscillation circuit, and λ is the pre-frequency dividing ratio of pre-frequency division module.

To sum up, use a kind of soil humidity sensor based on oscillation circuit provided by the present invention and method of work thereof, Two battery lead plates and the soil that is between two battery lead plates are considered as a capacitance to be measured by it to have the advantages that (1) Plane-parallel capacitor, then utilizes the relation of oscillation circuit frequency and the relation of capacitance and capacitance and dielectric constant, logical Cross the frequency values obtaining oscillation circuit, can be back-calculated to obtain the dielectric constant of soil, and then obtain the humidity value of soil, the most permissible Get rid of the defect that in traditional F DR and TDR method, the linearity is the highest, it is possible to quickly realize the quick, accurate and stable of soil moisture Measurement；(2) can be implemented in the single-point single-depth in certain area coverage, the quick soil humidity measuring of the many degree of depth of multiple spot； (3) use the output of Transistor-Transistor Logic level serial digital signal, can have the strongest capacity of resisting disturbance, possess long-distance transmissions ability；(4) Described soil humidity sensor also has that circuit structure is simple, with low cost and the feature such as application is convenient, practical, it is simple to real Border is promoted and uses.

Accompanying drawing explanation

In order to be illustrated more clearly that the embodiment of the present invention or technical scheme of the prior art, below will be to embodiment or existing In having technology to describe, the required accompanying drawing used is briefly described, it should be apparent that, the accompanying drawing in describing below is only this Some embodiments of invention, for those of ordinary skill in the art, on the premise of not paying creative work, it is also possible to Other accompanying drawing is obtained according to these accompanying drawings.

Fig. 1 is the structured flowchart of the soil humidity sensor based on oscillation circuit that the present invention provides.

Fig. 2 is the circuit diagram of the soil humidity sensor based on oscillation circuit that the present invention provides.

Fig. 3 is the method for work flow chart of the soil humidity sensor based on oscillation circuit that the present invention provides.

In above-mentioned accompanying drawing: 1, electric capacity 101, battery lead plate 2, oscillation module 3, counting module 4, processing module 5, divide in advance Frequency module.

Detailed description of the invention

Hereinafter with reference to accompanying drawing, describe, by way of example, the soil based on oscillation circuit that the present invention provides in detail Humidity sensor and method of work thereof.At this it should be noted that the explanation for these way of example is adapted to assist in understanding The present invention, but it is not intended that limitation of the invention.

The terms "and/or", a kind of incidence relation describing affiliated partner, can there are three kinds of passes in expression System, such as, A and/or B, can represent: individualism A, individualism B, there is tri-kinds of situations of A and B, the terms simultaneously "/and " it is to describe another kind of affiliated partner relation, two kinds of relations, such as, A/ and B can be there are, can represent: individually deposit in expression In two kinds of situations of A, individualism A and B, it addition, character "/" herein, typically represent forward-backward correlation and close liking a kind of "or" System.

Embodiment one

Fig. 1 shows the structured flowchart of the soil humidity sensor based on oscillation circuit that the present invention provides, and Fig. 2 shows The circuit diagram of soil humidity sensor based on oscillation circuit that the present invention provides, Fig. 3 show that the present invention provides based on shaking Swing the method for work flow chart of the soil humidity sensor in loop.Described based on oscillation circuit the soil that the present embodiment provides is wet Degree sensor is including plane-parallel capacitor 1, inductance L1, oscillation module 2, counting module 3 and processing module 4, wherein, described flat Parallel plate capacitor 1 includes two battery lead plates 101 and the fixing insulating part connecting two battery lead plates 101, makes two battery lead plates 101 mutual simultaneously Parallel, and respectively as the two poles of the earth of described plane-parallel capacitor 1；The two poles of the earth of described plane-parallel capacitor 1 are with described inductance L1 also Connection constitutes an oscillation circuit, and makes described oscillation circuit be sequentially connected in series described oscillation module 2, described counting module 3 and described Processing module 4.

As Fig. 1 is to shown in 2, and in the structure of described soil humidity sensor, described plane-parallel capacitor 1 is used for being inserted into In soil to be measured, thus can be by two battery lead plates 101 and be in the soil between two battery lead plates and be considered as a capacitance to be measured together Plane-parallel capacitor；Described oscillation circuit realizes the generation of oscillator signal for utilizing LC oscillation principle；Described oscillation module For described oscillation circuit is encouraged, produce oscillator signal；Described enumerator is based on carrying out the frequency of oscillator signal Number, obtains the frequency measurement of oscillator signal, and described frequency measurement is delivered to described processing module processes；Described place Reason module is for the capacitance according to plane-parallel capacitor 1 described in described frequency measurement Extrapolation and the dielectric of soil to be measured Constant, and then according to the relation of classical soil dielectric constant with soil moisture content, it is back-calculated to obtain the humidity value of soil to be measured (i.e. Soil moisture content).Additionally, as it is shown in figure 1, also include providing electric energy support for modules in described soil humidity sensor Power module.

As it is shown on figure 3, the method for work of described soil humidity sensor based on oscillation circuit can be, but not limited to include Plane-parallel capacitor is inserted in soil to be measured by following steps: S101.；S102. start oscillation module, oscillation circuit is carried out Excitation, produces oscillator signal；S103. described oscillator signal is imported counting module, by the counting of counting module, obtain described Frequency measurement f of oscillator signal；S104. processing module obtains described frequency measurement f, and reads parallel plate capacitor from this locality The battery lead plate area S of device and plate spacing d, then according to the DIELECTRIC CONSTANT ε of equation below calculating soil to be measured:

$\mathrm{\ϵ}=\frac{d}{{\mathrm{\ϵ}}_{0}SL{\left(2\mathrm{\π}f\right)}^2}$

In formula, ε₀For permittivity of vacuum, L is the inductance value of inductance in oscillation circuit；S105. calculate to be measured according to equation below The humidity value of soil

Then described humidity value is exportedThus By described soil humidity sensor and method of work thereof, the highest the lacking of the linearity in traditional F DR and TDR method can be got rid of Fall into, it is possible to quickly realize quick, the accurate and stable measurement of soil moisture.Further, it is also possible to realize in certain area coverage Interior single-point single-depth, the quick soil humidity measuring of the many degree of depth of multiple spot, the most described soil humidity sensor also has circuit The features such as simple in construction, with low cost and application are convenient, practical, it is simple to actual to promote and use.

Optimizing, described oscillation module 2 includes voltage controlled oscillator amplifier, the first electric capacity that model is MC100EL1648D C1, the 8th electric capacity C8, the 9th electric capacity C9, the first resistance R1 and the 3rd resistance R3；The 8th of described voltage controlled oscillator amplifier draws Foot BIAS connects one end of described 3rd resistance R3, the other end of described 3rd resistance R3 and described voltage controlled oscillator amplifier Described oscillation circuit in parallel between first pin TANK；Second pin VCC1 of described voltage controlled oscillator amplifier and the 3rd pin VCC2 is connected, and connects the described 8th electric capacity C8 and the described 9th electric capacity C9 of ground connection of ground connection the most respectively；Described VCO 5th pin AGC of device amplifier and the 7th pin VEE2 is connected, and then connects the described first electric capacity C1 of ground connection, the most successively Connect described first resistance R1 and DC source VCC；6th pin VEE1 ground connection of described voltage controlled oscillator amplifier, described pressure 4th pin OUT of controlled oscillator amplifier is as the outfan of described oscillation module 2.As in figure 2 it is shown, described voltage controlled oscillator Amplifier U3 is a kind of existing product being integrated with VCO function and signal amplifying function, and it so can be utilized voltage-controlled Described oscillation circuit is encouraged by oscillation functions, produces oscillator signal, and utilizes its signal amplifying function to described vibration letter Number it is amplified, in order to subsequent module can be identified processing.Additionally, described 3rd resistance R3 is used for producing oscillating current, Described first electric capacity C1, described 8th electric capacity C8 and described 9th electric capacity C9 for as shunt capacitance, protect described voltage-controlled shake Swinging device amplifier not affected by external communication signal, the oscillator signal finally produced is from the of described voltage controlled oscillator amplifier Four pin OUT outputs.

Optimize, 12 grade of two mechanism ripple counter that described counting module 3 includes that model is MC74HC4040AD, the 4th Resistance R4 and the 7th resistance R7；Tenth pin CLOCK of described 12 grade of two mechanism ripple counter is as described counting module 3 Input, and connect one end and one end of described 7th resistance R7 of described 4th resistance R4 respectively, described 4th resistance R4's 16th pin VCC1 of the other end and described 12 grade of two mechanism ripple counter connects DC source VCC respectively, and the described 7th The other end ground connection of resistance R7；8th pin GND ground connection of described 12 grade of two mechanism ripple counter, described 12 grade of two mechanism stricture of vagina 11st pin RESET of ripple enumerator connects the control output end of described processing module 4, described 12 grade of two mechanism ripple count 12 output pins of device are as the outfan of described counting module 3.As in figure 2 it is shown, described 12 grade of two mechanism ripple counter U1 is a kind of existing product that can count the clock signal frequency of input, and it can be with synchronism output 12 bit According to (frequency measurement i.e. counted to get may be up to 4.096kHz), so that described processing module is carried out, computing is counter to be pushed away.Additionally, institute State the 4th resistance R4 and described 7th resistance R7 for stably carrying out the oscillator signal in direction, self-excited oscillation loop (i.e. as clock signal The measured signal of input).

Concrete, described processing module 4 includes that model is the singlechip chip of STM8L151C8T6-48, the 3rd electric capacity C3 With the 5th resistance R5；Second pin PA1/NRST of described singlechip chip as the control output end of described processing module 4, and Connecting one end and one end of described 5th resistance R5 of described 3rd electric capacity C3 respectively, the other end of described 5th resistance R5 connects DC source VCC, the other end ground connection of described 3rd electric capacity C3.As in figure 2 it is shown, described 3rd electric capacity C3 and the 5th resistance R5 uses In stablizing control signal to be output, in order to control described counting module 3 exactly and reset, i.e. control described 12 grade of two machine Ripple counter processed resets.Also shown in FIG. 2, the tenth five to ten eight pin of described singlechip chip (PE1～ PE4), the the 40th the one to four ten four pin (PC2～PC5) and the the 20th the five to two ten eight pin (PB1～PE4) draw as input Foot, 12 output pins with described 12 grade of two mechanism ripple counter dock respectively, and the frequency of input reflection oscillator signal is surveyed 12 bit binary data of value；47th pin (PE6) of described singlechip chip and the 48th pin (PE7) are respectively As input and the outfan of internal data of external data, for carrying out wire communication with external equipment, input calculates ginseng Number (the battery lead plate area S of such as plane-parallel capacitor and plate spacing d etc.) or derivation soil moisture value, it can be, but not limited to Use Transistor-Transistor Logic level (transistor transistor logic, transistor-transistor logic level) serial digital signal defeated Go out, can have the strongest capacity of resisting disturbance, possess long-distance transmissions ability.

Concrete, between described oscillation module 2 and described counting module 3, it is in series with pre-frequency division module 5.Such as Fig. 1 and Fig. 2 Shown in, owing to the maximum count value of described counting module 3 is limited, the maximum count of the most described 12 grade of two mechanism ripple counter Value is 4096, it is difficult to meet high-frequency count demand, described prevention frequency module 5 of therefore connecting, and can reduce subsequent counter module 3 Output numerical value, prevents counting from overflowing, it is ensured that counting correctness.As optimize further, now according to equation below according to such as The DIELECTRIC CONSTANT ε of lower formula calculating soil to be measured:

$\mathrm{\ϵ}=\frac{d}{{\mathrm{\ϵ}}_{0}SL{\left(2\mathrm{\π}\mathrm{\λ}f\right)}^2}$

In formula, ε₀For permittivity of vacuum, L is the inductance value of inductance in oscillation circuit, and λ is the pre-frequency dividing ratio of pre-frequency division module.

Optimize further, between described oscillation module 2 and described pre-frequency division module 5 or at described pre-frequency division module 5 And it is in series with capacitance between described counting module 3.As in figure 2 it is shown, at described oscillation module 2 and described pre-frequency division module 5 Between be in series with the 6th electric capacity C6, between described pre-frequency division module 5 and described counting module 3, be in series with the 5th electric capacity C5, point Yong Yu dc component in oscillation-damped signal.It is MC12080D that described pre-frequency division module 5 can be, but not limited to use model Pre-distributor.As in figure 2 it is shown, described pre-distributor is that (1.1GHz is for the pre-divider high-frequency input signal of a kind of 1.1GHz The maximum operation frequency of this pre-divider), can be by configuring its 3rd pin SW1, the 6th pin SW2 and the 7th pin SW3 Level pre-frequency dividing ratio is set.As in figure 2 it is shown, described 3rd pin SW1 is configured to low level, described 6th pin SW2 joins Being set to high level, described 7th pin SW3 is configured to low level, and thus can arrange pre-frequency dividing ratio is 40, the frequency that can record Measured value can reach 40 × 4.096kHz, meets basic measurement demand.

Concrete, the outer surface of described battery lead plate 101 is provided with zinc coat.By arranging described zinc coat, it is possible to prevent electricity Pole plate gets rusty, it is to avoid affect electrode characteristic and capacitance, especially at described battery lead plate when being inserted into soil to be measured.

To sum up, soil humidity sensor based on oscillation circuit that the present embodiment is provided and method of work thereof, have as Lower beneficial effect: (1) its two battery lead plates and the soil that is between two battery lead plates are considered as the parallel-plate of a capacitance to be measured Capacitor, then utilizes the relation of oscillation circuit frequency and the relation of capacitance and capacitance and dielectric constant, by obtaining The frequency values of oscillation circuit, can be back-calculated to obtain the dielectric constant of soil, and then obtains the humidity value of soil, so can get rid of biography The defect that in system FDR and TDR method, the linearity is the highest, it is possible to quickly realize quick, the accurate and stable measurement of soil moisture； (2) can be implemented in the single-point single-depth in certain area coverage, the quick soil humidity measuring of the many degree of depth of multiple spot；(3) use Transistor-Transistor Logic level serial digital signal exports, and can have the strongest capacity of resisting disturbance, possess long-distance transmissions ability；(4) described soil Humidity sensor also has that circuit structure is simple, with low cost and the feature such as application is convenient, practical, it is simple to actual promote and Use.

As it has been described above, the present invention can preferably be realized.For a person skilled in the art, according to the religion of the present invention Leading, soil humidity sensor based on oscillation circuit and the method for work thereof of designing multi-form are not required to creative labor Dynamic.Without departing from the principles and spirit of the present invention these embodiments are changed, revise, replace, integrate and become Type still falls within protection scope of the present invention.

Claims (10)

1. a soil humidity sensor based on oscillation circuit, it is characterised in that include plane-parallel capacitor (1), inductance (L1), oscillation module (2), counting module (3) and processing module (4), wherein, described plane-parallel capacitor (1) includes two electrodes Plate (101) and the fixing insulating part connecting two battery lead plates (101), make two battery lead plates (101) be parallel to each other simultaneously, and respectively as The two poles of the earth of described plane-parallel capacitor (1)；

The two poles of the earth of described plane-parallel capacitor (1) one oscillation circuit of composition in parallel with described inductance (L1), and make described vibration Loop is sequentially connected in series described oscillation module (2), described counting module (3) and described processing module (4).

A kind of soil humidity sensor based on oscillation circuit, it is characterised in that described oscillation mode Block (2) include voltage controlled oscillator amplifier that model is MC100EL1648D, the first electric capacity (C1), the 8th electric capacity (C8), the 9th Electric capacity (C9), the first resistance (R1) and the 3rd resistance (R3)；

8th pin (BIAS) of described voltage controlled oscillator amplifier connects one end of described 3rd resistance (R3), described 3rd electricity Described oscillation circuit in parallel between the other end and first pin (TANK) of described voltage controlled oscillator amplifier of resistance (R3)；

Second pin (VCC1) of described voltage controlled oscillator amplifier is connected with the 3rd pin (VCC2), connects ground connection the most respectively Described 8th electric capacity (C8) and described 9th electric capacity (C9) of ground connection；

5th pin (AGC) of described voltage controlled oscillator amplifier is connected with the 7th pin (VEE2), then connects the institute of ground connection State the first electric capacity (C1), be sequentially connected in series described first resistance (R1) and DC source (VCC) simultaneously；

6th pin (VEE1) ground connection of described voltage controlled oscillator amplifier, the 4th pin of described voltage controlled oscillator amplifier (OUT) as the outfan of described oscillation module (2).

A kind of soil humidity sensor based on oscillation circuit, it is characterised in that described count module Block (3) includes 12 grade of two mechanism ripple counter, the 4th resistance (R4) and the 7th resistance (R7) that model is MC74HC4040AD；

Tenth pin (CLOCK) of described 12 grade of two mechanism ripple counter is as the input of described counting module (3), and divides Do not connect one end and one end of described 7th resistance (R7) of described 4th resistance (R4), the other end of described 4th resistance (R4) DC source (VCC), described 7th electricity is connected respectively with the 16th pin (VCC1) of described 12 grade of two mechanism ripple counter The other end ground connection of resistance (R7)；

8th pin (GND) ground connection of described 12 grade of two mechanism ripple counter, the of described 12 grade of two mechanism ripple counter 11 pins (RESET) connect the control output end of described processing module (4), 12 of described 12 grade of two mechanism ripple counter Output pin (Q1～Q12) is as the outfan of described counting module (3).

A kind of soil humidity sensor based on oscillation circuit, it is characterised in that described process mould Block (4) includes that model is the singlechip chip of STM8L151C8T6-48, the 3rd electric capacity (C3) and the 5th resistance (R5)；

Second pin (PA1/NRST) of described singlechip chip is as the control output end of described processing module (4), and difference Connecting one end and one end of described 5th resistance (R5) of described 3rd electric capacity (C3), the other end of described 5th resistance (R5) is even Connect DC source (VCC), the other end ground connection of described 3rd electric capacity (C3).

A kind of soil humidity sensor based on oscillation circuit, it is characterised in that in described vibration Pre-frequency division module (5) it is in series with between module (2) and described counting module (3).

A kind of soil humidity sensor based on oscillation circuit, it is characterised in that in described vibration Connect between described counting module (3) between module (2) with described pre-frequency division module (5) or described pre-frequency division module (5) There is capacitance.

A kind of soil humidity sensor based on oscillation circuit, it is characterised in that described pre-frequency dividing Module (5) uses model to be the pre-distributor of MC12080D.

A kind of soil humidity sensor based on oscillation circuit, it is characterised in that at described electrode The outer surface of plate (101) is provided with zinc coat.

9. a method of work for the soil humidity sensor based on oscillation circuit as described in claim 1 to 8 any one, It is characterized in that, comprise the steps:

S101. plane-parallel capacitor is inserted in soil to be measured；

S102. start oscillation module, oscillation circuit is encouraged, produce oscillator signal；

S103. described oscillator signal is imported counting module, by the counting of counting module, obtain the frequency of described oscillator signal Measured value f；

S104. processing module obtain described frequency measurement f, and from this locality read plane-parallel capacitor battery lead plate area S and Plate spacing d, then according to the DIELECTRIC CONSTANT ε of equation below calculating soil to be measured:

$\mathrm{\ϵ}=\frac{d}{{\mathrm{\ϵ}}_{0}SL{\left(2\mathrm{\π}f\right)}^2}$

In formula, ε₀For permittivity of vacuum, L is the inductance value of inductance in oscillation circuit；

S105. the humidity value of soil to be measured is calculated according to equation below

Then described humidity value is exported

The method of work of a kind of soil humidity sensor based on oscillation circuit, its feature exists In, when being in series with pre-frequency division module between described oscillation module and described counting module, then according to equation below according to such as The DIELECTRIC CONSTANT ε of lower formula calculating soil to be measured:

$\mathrm{\ϵ}=\frac{d}{{\mathrm{\ϵ}}_{0}SL{\left(2\mathrm{\π}\mathrm{\λ}f\right)}^2}$

In formula, ε₀For permittivity of vacuum, L is the inductance value of inductance in oscillation circuit, and λ is the pre-frequency dividing ratio of pre-frequency division module.