CN2422643Y

CN2422643Y - Soil moisture measuring sensor

Info

Publication number: CN2422643Y
Application number: CN 00233573
Authority: CN
Inventors: 王一鸣
Original assignee: China Agricultural University
Current assignee: China Agricultural University
Priority date: 2000-05-25
Filing date: 2000-05-25
Publication date: 2001-03-07
Anticipated expiration: 2010-05-25

Abstract

The utility model discloses a sensor for measuring soil moisture, which comprises a casing 1, a circuit board 4, a coaxial cable transmission line 2, a high frequency oscillator 3 connected with the coaxial cable transmission line 2, a central probe head 7, and a peripheral probe head 6 connected with a shielding layer of the coaxial cable transmission line 2. The sensor for measuring soil moisture is characterized in that the circuit board 4 also comprises a detection filter circuit. The rectification filter circuit is composed of a detector diode 2AP30E and two segments of a II type filter circuit composed of a resistor and a capacitor. Both ends of the coaxial cable transmission line 2 are respectively connected to the input end 11 and 12 of the rectification filter circuit. The sensor for measuring soil moisture has the advantages of good service performance, simple structure, low cost, etc.

Description

New soil moisture measurement sensor

The utility model relates to a kind of sensor that is used for the measured soil volume moisture content.

The agricultural weather monitoring, soil moisture content monitoring and Irrigation Forecast, soil moisture measurement and control in agricultural, water conservancy, the ecospheres such as intelligent irrigation control system, all needing a kind ofly has than high measurement accuracy, stability and reliability height, input, output characteristics and real-time all can satisfy the soil moisture measurement sensor of the actual requirement of engineering.Soil moisture measurement sensor of having succeeded in developing and instrument have neutron measurement soil moisture instrument, time domain reflectometry (TDR) instrument, plaster block resistance etc. are though these soil moisture measurement sensors and instrument successfully have been applied to have certain limitation in scientific research and the production.Neutron measurement soil moisture instrument because radioactive source is arranged, requires the pre-buried aluminum casing of putting into inserting tube well of on-the-spot measuring point, shields.Otherwise cause radiation leakage, be detrimental to health, contaminated environment.Time domain reflectometry (TDR) soil water measuring instrument can be realized real-time fast the measurement, and the precision height because technology realizes that difficulty is big, therefore costs an arm and a leg, for example, and present " TRASE " soil moisture measurement system (TDR method), 19100 dollars of prices by U.S.'s import.Be not suitable in China produces, applying.

The purpose of this utility model is to provide a kind of usability good, simple in structure, the soil moisture measurement sensor that cost is low.

Comprise shell 1 in order to reach the technical scheme that the purpose of this utility model takes, wiring board 4, be contained in the coaxial cable transmission line 2 on the wiring board 4, the high frequency oscillator 3 that links to each other with an end 8 of coaxial cable transmission line 2, the center probe 7 that is installed in the other end of coaxial cable transmission line 2 reaches the periphery probe 6 that is connected with the screen layer of coaxial cable transmission line 2, it is characterized in that, wiring board 4 also comprises detection filter circuit, and the П type filtering circuit that this detection filter circuit is made up of resistance, electric capacity detector diode 2AP30E and two joints is formed; One end 8 of coaxial cable transmission line 2 is connected to the input end 11 of detection filter circuit, and the other end 9 of coaxial cable transmission line 2 is connected to another input end 12 of detection filter circuit;

Being connected to detachable connection the such as screw thread between center probe 7 and the shell 1;

A detachable lower cover 10 is made in the bottom of shell 1, is embedded with fixed cover 5 at the center of this detachable lower cover 10, and center probe 7 is fixed in the fixed cover 5 by being threaded, and also is embedded with the annular copper billet nut 14 that seals in the lower cover 10; Three peripheral probes 6 are popped one's head in 7 secured in parallel on lower cover 10 with the center, and ground wire loop 13 is connected as a single entity three peripheral probes 6; Center probe 7 is than peripheral probe 6 length.

Shell 1, lower cover 10 are made of plastics, and the material of fixed cover 5 is a copper, and the material of center probe 7 and peripheral probe 6 is a stainless steel.

Major advantage of the present utility model is: cost is low, measures applied widelyly, and dynamic response is fast.

Fig. 1 is the utility model soil moisture measurement sensor system composition diagram.

Fig. 2 is the utility model soil moisture measurement sensor structural representation

Fig. 3 is the detection filter circuit figure of the utility model soil moisture measurement sensor.

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

As shown in Figure 1,1 is high frequency oscillator, and 2 is coaxial cable transmission line, and 7 are the center probe, and 6 is three peripheral probes.High frequency oscillator 1 is connected to an end 8 of coaxial cable transmission line 2.Probe is made up of four stainless steel bars, and peripheral probe 6 is connected to the screen layer of coaxial cable transmission line 2 by ground wire loop 13, and an end of center probe 7 is connected to the internal layer signal line end 9 of coaxial cable transmission line.

As shown in Figure 2,1 is shell, and 7 are the center probe, and 6 is peripheral probe, 4 is wiring board, and 14 is the annular copper billet nut that seals, the 13 ground wire loops for three peripheral probes 6 of short circuit, 10 is detachable lower cover, and 5 for being embedded in the fixed cover in the

lower cover

10, and 15 is quad.In order to adapt to the different measuring scope, the length of center probe 7 is respectively 6 centimetres, 10 centimetres, 15 centimetres, 20 centimetres, and diameter is 6 millimeters, and it is fixed on by being threaded on the fixed cover 5, and the length of three peripheral probes 6 is 3 centimetres.The employing of fixed cover 5 and annular copper billet nut 14 makes the user require to select easily the center of appropriate length to pop one's head in according to measuring soil depth.

Wiring board 4 is made up of high frequency oscillator 1, coaxial cable transmission line 2 and detection filter circuit, detection filter circuit as shown in Figure 3, the П type filtering circuit that it is made up of resistance, electric capacity detector diode 2AP30E and two joints is formed.

Two core leads of quad 15 connect direct supply+12V and two ends, ground respectively, and other two core leads are a end and the b end of connection layout 3 detection filter circuits respectively, as the output terminal of direct-flow signal voltage.The other end of quad connects meter specially or data acquisition unit.

The sensor power supply is voltage 5-12V, the direct supply of electric current 40-80mA or battery.

8 ends of Fig. 1 standard coaxial cable transmission line 2 are connected to the input end 11 of the detection filter circuit among Fig. 3, and 9 ends of coaxial cable transmission line 2 are connected to another input end 12 of Fig. 3 detection filter circuit.The output dc voltage Vab of detection filter circuit represents volumetric water content of soil.

For thin solum (in 20 centimetres of degree of depth), the user selects the center probe of appropriate length, after installing, in the vertical insertion of sensor soil to be measured, the signal output cable is connected to measurement instrument or data acquisition unit, shows volumetric water content of soil.For deep soil (20 centimetres more than the degree of depth), selecting active length is 6 centimetres center probe, after installing, sensor is imbedded the premeasuring position, the signal output cable is connected to measurement instrument or data acquisition unit can carry out continuous location survey.

After sensor probe inserts soil, high frequency oscillator produces 50MHz to 100MHz sine wave signal, this electromagnetic wave is propagated in soil by coaxial cable transmission line, the variation of soil moisture content, cause the variation of soil dielectric constant and impedance, occur the crest and the trough of standing wave at the two ends of coaxial cable transmission line 2, and cause the change in voltage at two ends, the sinusoidal signal voltage at coaxial cable transmission line two ends is transformed to DC voltage through the two-way detection filter circuit.By measuring this dc voltage measurement volumetric water content of soil.

In experiment, this soil moisture measurement sensor dynamic response is fast, gets final product reading in 1 second, and cost is starkly lower than time-domain reflectomer (TDR), is suitable for using aborning.

Claims

1, a kind of new soil moisture measurement sensor comprises shell (1), wiring board (4), be contained in the coaxial cable transmission line (2) on the wiring board (4), the high frequency oscillator (3) that links to each other with an end (8) of coaxial cable transmission line (2), the center probe (7) that is installed in the other end of coaxial cable transmission line (2) reaches the periphery probe (6) that is connected with the screen layer of coaxial cable transmission line (2), it is characterized in that, wiring board (4) also comprises detection filter circuit, and this detection filter circuit is saved by resistance by detector diode 2AP30E and two, the II type filtering circuit that electric capacity is formed is formed; One end (8) of coaxial cable transmission line (2) is connected to the input end (11) of detection filter circuit, and the other end (9) of coaxial cable transmission line (2) is connected to another input end (12) of detection filter circuit; Being connected to detachable connection the such as screw thread between center probe (7) and the shell (1).

2, new soil moisture measurement sensor according to claim 1, it is characterized in that, the bottom of shell (1) is a detachable lower cover (10), be embedded with fixed cover (5) at the center of this lower cover (10), center probe (7) is fixed in by being threaded in the fixed cover (5), also is embedded with the annular copper billet nut (14) that seals in the lower cover (10); Three peripheral probes (6) are popped one's head in (7) secured in parallel on lower cover (10) with the center, and ground wire loop (13) is connected as a single entity three peripheral probes (6); Center probe (7) is longer than peripheral probe (6);

3, new soil moisture measurement sensor according to claim 1 is characterized in that, shell (1) is made of plastics, and the material of center probe (7) and peripheral probe (6) is a stainless steel.

4, new soil moisture measurement sensor according to claim 2 is characterized in that, shell (1), lower cover (10) are made of plastics, and the material of fixed cover 5 is a copper, and the material of center probe (7) and peripheral probe (6) is a stainless steel.