CN201225993Y

CN201225993Y - Soil moisture sensor

Info

Publication number: CN201225993Y
Application number: CNU2008200486838U
Authority: CN
Inventors: 罗锡文; 胡均万; 阮欢; 李就好
Original assignee: South China Agricultural University
Current assignee: South China Agricultural University
Priority date: 2008-06-03
Filing date: 2008-06-03
Publication date: 2009-04-22
Anticipated expiration: 2018-06-03

Abstract

The utility model discloses a soil-water sensor which includes a shell (3), a probe (1) for the water rate of soil arranged at the bottom part of the shell (3) and a detection circuit (4) arranged in the shell (3); the detection circuit (4) gives out a pulse square wave actuating signal to the probe (1) for the water rate of soil and receives the peak value signals of the charging voltages at the two ends; the detection circuit (4) includes a processor (5), a capacitance (C1) and a wave detection circuit; the processor (5) is connected with the triggering end of the probe (1) for the water rate of soil respectively through the capacitance (C1) and the wave detection circuit and is connected with an external communication interface through a communication opening on the processor (5); the grounding end f the probe (1) for the water rate of soil is grounded. The soil-water sensor has the advantages of accurate measuring, simple structure and lower cost.

Description

A kind of soil moisture sensor

Technical field

The utility model relates to the field information acquisition field, relates in particular to a kind of soil moisture sensor.

Background technology

In precision agriculture was produced, precisely irrigation required long term monitoring and in time obtains the soil moisture space distribution information in field, and this just need install the soil moisture proving installation in the field.

Ripe at present soil moisture content detection method has TDR (time domain reflectometry), FDR (frequency domain reflectometry) and SWR (standing wave ratio method), wherein TDR and FDR are external patented technologies, measuring accuracy is than higher, but because the treatment circuit complexity causes cost high, a TDR is up to tens thousand of dollars, and a FDR is up to thousands of dollars; SWR soil moisture content sensor has adopted accurate signal source can make cost be reduced to 600 yuans by the method for measuring standing wave ratio.Because the average yield in every mu of paddy rice every year is less than 300 yuan, thus TDR and FDR can not apply in the field, even the minimum SWR of cost also is difficult to promote in the field.

China Patent No. CN2422643 discloses a kind of new soil moisture measurement sensor, the periphery probe that this utility model is used high frequency oscillator to produce high-frequency signal injection center probe and is connected with the screen layer of coaxial cable transmission line comes measured soil moisture by detecting circuit again.CN1719245 discloses the method and the sensor of a kind of synchronous real-time measurement soil moisture and conductivity, this utility model patent be a kind of based on dielectric the method and the sensor of measured soil moisture and conductivity theoretical and frequency domain method the time.Adopt the admittance of the direct measuring sonde of multi-frequency admittance decomposition method, and then decompose the real part and the imaginary part of probe admittance, the relation by probe admittance real part and dielectric loss draws the dielectric conductance rate, and the relation of the admittance imaginary part of popping one's head in and specific inductive capacity draws the media water-bearing rate.CN2854589 discloses a kind of based on a kind of soil moisture measurement sensor of edge effect with the capacitance measurement moisture.With soil moisture sensor ratio in the past, can measure the moisture of different depth soil effectively.CN2641646 discloses a kind of soil moisture content pick-up unit based on dielectric method, has eliminated the measuring error that causes because of the inconsistent of oscillation amplitude and output resistance, and performance is more stable.CN1619301 discloses a kind of dielectric frequency difference formula soil moisture sensor, comprises soil electrode, oscillatory circuit, amplification and rectification circuit, multistage frequency dividing circuit, low-pass filter circuit and photoelectric isolating circuit composition, exports the frequency signal relevant with soil moisture.

Above-mentioned patented technology has mostly used the high-frequency concussion to export and plant in soil moisture relevant voltage or frequency with signal processing circuit, obtain the digital signal of soil moisture, also must increase ADC Acquisition Circuit or frequency measurement circuit, because the hardware circuit more complicated, cost is difficult to reduce.

CN101017133 discloses a kind of soil water measuring instrument based on infrared radiation, mainly by infrared emission circuit, photo-detector, red emission circuit and be placed on photo-detector and the pedotheque box in the middle of condenser system forms, different in moisture is made the different principle of its degree of absorption when utilizing certain wavelength near infrared ray to shine testee.CN200968934 discloses a kind of name and has been called a kind of soil moisture sensor based on optical fiber surface plasmon resonance, by stainless steel filter cap, moisture-sensitive film, the Au film, the dome-type prism, optical fiber and moisture transducer probe are formed, and obtain the content of soil moisture from the spectral information of fiber reflection.Owing to adopted pure method of optics, thereby reduced the influence of soil types and soil particle size, improved the sensitivity and the degree of accuracy of moisture measurement measurement result, but complicated optical system and and supporting signal processing circuit be difficult to reduce cost.

The utility model content

At the shortcoming of prior art, the purpose of this utility model provides accurate, the simple in structure and lower-cost soil moisture sensor of a kind of measurement.

For achieving the above object, the technical solution of the utility model is: a kind of soil moisture sensor, the testing circuit that it comprises shell, is arranged at the soil moisture content probe of outer casing bottom and is located at enclosure, this testing circuit sends the pulse square wave pumping signal and receives the peak signal of its two ends charging voltage to the soil moisture content probe.

Testing circuit comprises processor, capacitor C 1 and detecting circuit, processor is connected with the trigger end of soil moisture content probe by capacitor C 1 and detecting circuit respectively, and be connected the earth terminal ground connection of soil moisture content probe with outside communication device by the communication port on the processor; Detecting circuit comprises detector diode D2 and filter capacitor C2, and the positive pole of detector diode D2 is connected with the trigger end of soil moisture content probe, and negative pole is by filter capacitor C2 ground connection.

Processor comprises following functional module:

Timer is used for the soil moisture content probe is sent the pulse square wave pumping signal;

Digital to analog converter is used for converting the peak value of the charging voltage at the soil moisture content probe two ends of detecting circuit output to digital signal;

Computing module is according to testing the water percentage that the formula of demarcating calculates soil automatically;

Communication module is sent to outside communication device with the soil moisture content data message that calculates.

Soil moisture content probe trigger end and earth terminal parallel interval are provided with; Shell is column type or square column type.

Compared with prior art, the utility model adopts the soil moisture content probe to come the water percentage of measured soil, and utilize pulse square wave signal that processor produces pumping signal as probe, detecting circuit is used for the charging voltage peak value of measuring probe, utilize processor that aanalogvoltage is converted to digital voltage, and calculate the water percentage of soil.This structure replaces complicated high frequency oscillation circuit with the method that processor produces pulse signal, only needs one group of probe and testing circuit can collect the moisture measurement signal of soil, and simple in structure and easy to use, the while also greatly reduces cost of manufacture.

Description of drawings

Fig. 1 is the structural representation of the utility model soil moisture sensor;

Fig. 2 is the another kind of structural representation of the utility model soil moisture sensor;

Fig. 3 is the fundamental diagram of the utility model testing circuit;

Fig. 4 is the graph of relation of the utility model soil moisture content and charging crest voltage.

Embodiment

The utility model is described in further detail below in conjunction with accompanying drawing.

Contain moisture and impurity in the soil, wherein water has important dielectric that electrically conductive particles is also arranged, the electrode that inserts in the soil can equivalence be a RC parallel circuit, under the electrode insertion depth does not become situation, the resistivity of soil and dielectric coefficient are by the water percentage decision of soil, the resistance of the equivalent resistance of the electrode of the regular length in the insertion soil and the water percentage inverse ratio of soil are because the capacity of equivalent capacity is directly proportional with the water percentage of soil.The RC that measures this electrode just changes the water percentage in can measured soil.

According to above principle, the utility model discloses a kind of soil moisture sensor, as shown in Figure 1, the testing circuit 4 that it comprises shell 3, is arranged at the soil moisture content probe 1 of shell 3 bottoms and is located at shell 3 inside, this testing circuit 4 is electrically connected with soil moisture content probe 1, and this testing circuit 4 sends the pulse square wave pumping signal and receives the peak signal of its two ends charging voltage to soil moisture content probe 1.In the present embodiment, the quantity of soil moisture content probe 1 trigger end and earth terminal is one, and trigger end and the setting of earth terminal parallel interval.Certainly, the earth terminal of soil moisture content probe 1 can be a plurality of, and its structure is the centre that the trigger end of soil moisture content probe 1 is located at shell 3 bottoms, and earth terminal is evenly distributed on the periphery of shell 3 bottoms.

Above-mentioned shell 3 is the ambroin pipe of hollow, the lower end water-tight, and middle space is used for mounting testing circuit 4 and supplies the battery of testing circuit 4 usefulness, and the cable-through hole of soil moisture content probe 1 is installed in shell 3 bottoms, and with marine glue it is sealed.Shell 3 is square column type or column type, as shown in Figures 1 and 2.

As shown in Figure 3, testing circuit 4 comprises processor 5, capacitor C 1 and detecting circuit, processor 5 is connected with the trigger end of soil moisture content probe 1 by capacitor C 1 and detecting circuit respectively, and be connected by the communication device of the communication port on the processor 5 with the outside, promptly processor 5 sends to data in wireless communication module or the secondary instrument.The earth terminal ground connection of soil moisture content probe 1.Detecting circuit comprises detector diode D2 and filter capacitor C2, and the positive pole of detector diode D2 is connected with the trigger end of soil moisture content probe 1, and negative pole is by filter capacitor C2 ground connection.The earth terminal of this soil moisture content probe 1 also connects the negative pole of diode D1, and the positive pole of diode D1 is connected to the negative pole of detector diode D2.

Above-mentioned processor comprises following functional module:

Wherein, timer produces the pulse square wave signal of 20kHz, exports soil moisture content probe 1 to as pumping signal by capacitor C 1.When pulse was in high level, to the equivalent capacity charging that probe is formed, the equivalent capacity of soil moisture content probe 1 was by the resistivity and the dielectric coefficient decision of soil, and when pulse was zero level, the equivalent capacity of probe was by the equivalent resistance discharge of self.For fixing duration of charging and discharge time, the charging voltage at probe two ends is by the RC characteristic decision of probe, so the charging crest voltage of measuring probe just can calculate the soil moisture content of soil moisture content probe 1.

Detector diode D2 and filter capacitor C2 constitute the detecting circuit of soil moisture content probe 1, are used for the charging crest voltage of measured soil water percentage probe 1.This processor 5 is a single-chip microcomputer, and its inner integrated digital to analog converter ADC converts 0～1023 digital signal to, and utilizes the formula of demarcating in the computing module to calculate the water percentage of soil the DC voltage of detecting circuit output.The relation of the soil moisture content that calibration formula draws by repetition test and the charging crest voltage at soil moisture content probe 1 two ends is summed up and is drawn, as shown in Figure 4.

Claims

1, a kind of soil moisture sensor, it is characterized in that comprising shell (3), be arranged at the soil moisture content probe (1) of shell (3) bottom and be located at the inner testing circuit (4) of shell (3) that this testing circuit (4) sends the pulse square wave pumping signal and receives the peak signal of its two ends charging voltage to soil moisture content probe (1).

2, soil moisture sensor according to claim 1, it is characterized in that: testing circuit (4) comprises processor (5), electric capacity (C1) and detecting circuit, processor (5) is connected with the trigger end of soil moisture content probe (1) by electric capacity (C1) and detecting circuit respectively, and the communication port that passes through on the processor (5) is connected the earth terminal ground connection of soil moisture content probe (1) with the communication device of outside.

3, soil moisture sensor according to claim 2, it is characterized in that: detecting circuit comprises detector diode (D2) and filter capacitor (C2), the positive pole of detector diode (D2) is connected with the trigger end of soil moisture content probe (1), and negative pole is by filter capacitor (C2) ground connection.

4, soil moisture sensor according to claim 1 is characterized in that: processor (5) comprises following functional module:

Timer is used for soil moisture content probe (1) is sent the pulse square wave pumping signal;

5, according to each described soil moisture sensor of claim 1 to 4, it is characterized in that: soil moisture content probe (1) trigger end and earth terminal parallel interval are provided with.

6, soil moisture sensor according to claim 5 is characterized in that: shell (3) is column type or square column type.