JPH0338687Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention measures the moisture contained in soil, bed soil for plant cultivation, organic matter such as compost, and porous materials such as sphagnum moss, peat, and rock wool. This invention relates to a sensor for measuring moisture.

(Prior Art) One of the methods for measuring moisture contained in soil, etc. is the tensiometer method. As shown in Fig. 4, a conduit 2 equipped with a tensio cup 1 made of a porous and highly rigid material is buried in the soil, and the water filled in the tensio cup 1 balances with the capillary force of the soil via the tensio cup 1. The negative pressure generated when the mercury column reaches 3 is read as the height of the mercury column 3, or as shown in Figure 5, the internal pressure of the conduit 2 is read from the scale of the vacuum gauge 4 and displayed as soil water tension (pF value). be. In the figure, 5 is a connecting tube and 6 is an air pool.

Measurement using the tensiometer method in the prior art has the characteristic that moisture can be measured as a suction force or equilibrium negative pressure caused by the capillary retention force of soil, etc., but since this negative pressure is minute, it can be measured electrically. It was difficult to take it out. For this reason, in the past, the water content had to be measured by reading the height of the mercury column or the pointer (scale) of a vacuum gauge. However, the conventional technology uses mercury, which poses an environmental pollution problem.
There are problems such as concerns about the accuracy of the vacuum gauge.

In addition, plants grow at a specific depth from the ground depending on their type, so simply knowing the moisture content of the soil, etc. can determine whether the moisture required for the growth of the plant is being met. I can't do it. However, although moisture measuring instruments according to the prior art can measure soil moisture near the ground surface, they cannot measure moisture at a specified depth.
Here, it is important to accurately measure the moisture at a specific depth from the ground surface in soil etc., for example, in order to control the irrigation system in the summer dry season of orchards.

(Problem to be solved by the invention) The problem to be solved by the invention is to develop a moisture sensor that can continuously and highly accurately measure moisture at specific depths from the surface of soil etc. over a long period of time. The goal is to provide the following.

(Means for solving the problem) The means for solving the problem in this invention are as follows:
A pipe of a predetermined length, a porous cup made of a porous and highly rigid material detachably connected to the lower end of the pipe, a cover screwed to the upper end of the pipe, and attached to the lower surface of the upper wall of the cover. a piezoelectric element connected to the piezoelectric element, a lead wire connected to the piezoelectric element to electrically transmit the output of the piezoelectric element, and a lower end fixed to the bottom wall of the cover and an upper end connected to the piezoelectric element in order to transmit the water pressure in the pipe to the piezoelectric element. a pressure sensing element held in contact with the pressure sensing element; a pressure transmission tube connected to the pressure sensing element with its tip facing into the pipe; an inlet that can be opened and closed near the upper end of the pipe; It is characterized by comprising a water injection tube that reaches into the pipe, and an exhaust port that is provided in the pipe above the injection port and can be opened and closed.

(Function) To measure the moisture in soil, etc., after filling the inside of the pipe 10, porous cup 11, bellows 17, and pressure transmission tube 21 with water, the water injection pot 25 and the exhaust pot 26 are closed, and the pipe is closed. 1
0 in a porous material (soil).

Porous cup 1 depending on the moisture level of soil etc.
Water in the cup flows in and out from the pipe 10, thereby changing the internal pressure of the pipe 10. Since this internal pressure is transmitted to the bellows 17 via the pressure transmission tube 21, the pressure contact force of the piezoelectric element 6 changes due to the expansion and contraction of the bellows 17. Then, the moisture contained in the soil or the like is measured based on the electrical signal of the piezoelectric element 16 outputted from the input/output terminal 18.

(Example) FIGS. 1 to 3 show a moisture sensor according to the present invention. In these figures, a porous cup 1 is attached to the lower end of a pipe 10 of a predetermined length made of a highly rigid material that is corrosion-resistant and water-impermeable.
1 is connected, and the lower end opening of this porous cup 11 is closed with a conical tip cone 12. Note that the pipe 10 and porous cup 11 are as follows:
Specifically, a male thread 14 is screwed to a female connection thread 13 fixed to the lower end of the pipe 10.
The porous cup 11 is fixed to the male thread 14. Therefore, the porous cup 11 and the male thread 14 are removably connected to the lower end of the pipe 10. The porous cup 11 is made of a porous and highly rigid material.

A cover 15 is screwed to the upper end of the pipe 10, and a piezoelectric element 16 having a piezo effect is attached to the lower surface of the upper wall 15a of the cover 15.
Further, the lower end of a bellows 17 as a pressure sensing element is fixed to the bottom wall 15b of the cover 15, and a protrusion 17a provided at the center of the upper end of the bellows 17 is held in contact with the piezoelectric element 16 from below with a predetermined pressure. , an input/output terminal 18 provided outside the cover 15 and the piezoelectric element 16 are connected by a lead wire 19. Note that 20 is a rainproof cover.

On the other hand, a pressure transmission tube 21 is provided inside the pipe 10 to maintain communication between the inside of the bellows 17 and the bottom of the pipe 10. A water injection tube 23 is provided that reaches the inner part of 11. Further, an exhaust port 24 is provided near the upper end of the pipe 10, and a water injection port 25 and an exhaust port 26 for opening and closing the water injection port 22 and the exhaust port 24 are provided. Reference numeral 27 denotes an exhaust guide provided at the upper end of the pipe 10.

In order to measure moisture using the moisture sensor configured in this way, after filling the inside of the pipe 10, porous cup 11, bellows 17, and pressure transmission tube 21 with water, the water injection cup 25 and the exhaust cup are filled with water. 26 is closed and the pipe 10 is buried in the porous material (soil), and the porous cup 11 is closed.
installed at a specified depth.

When the porous cup 11 is embedded to a predetermined depth, the porous cup 1 is buried according to the water tension of the porous material in contact with the outer peripheral surface of the porous cup 11.
Water in the cup flows in and out through the porous cup 11, and the water tension in the pipe 10 reaches an equilibrium state via the porous cup 11.

When the internal pressure of the pipe 10 changes, the internal pressure of the bellows 17, which is maintained in communication with the inside of the pipe 10 via the pressure transmission tube 21, changes. Then, as the internal pressure changes, the bellows 17 expands and contracts to change the pressing force on the piezoelectric element 16, so that the electrical characteristics output from the input/output terminal 18 change. Therefore, the moisture content of the soil or the like can be measured by the electrical signal of the piezoelectric element 16 output from the input/output terminal 18.

Incidentally, since the internal pressure of the pipe 10 is doubled by the bellows 17 and applied to the piezoelectric element 16, even slight pressure fluctuations can be accurately measured, and measurement accuracy can be increased.

Also, when the water in the pipe 10 decreases or air bubbles accumulate, open the water inlet 25 and the exhaust outlet 26, and use a syringe or the like to fill the water inlet 22.
Inject water into. Then, water is supplied from the water inlet 22 to the inside of the porous cup 11 (bottom of the pipe 10) through the water inlet tube 23, so water can be filled by continuing to inject water until water comes out from the exhaust port 24. I can do it. After filling with water, the measurement can be easily restarted by closing the water injection tank 25 and the exhaust tank 26 again.

If the piezoelectric element 16 is made of pressure-sensitive conductive rubber, minute pressure changes can be detected more accurately, and this pressure change can be extracted as a voltage change, making it possible to measure moisture content over a wide range with high sensitivity. At the same time, it is possible to reduce the size, weight, and cost of the sensor.

(Effects of the invention) In this invention, a cover with a piezoelectric element etc. is screwed to the upper end of the pipe, and a porous cup provided at the lower end is detachably attached. Moisture can be measured at a specific depth from the ground surface. Therefore, when monitoring soil moisture, it is possible to accurately measure moisture at each depth specified according to the type of plant being cultivated. There is an effect that can be done.

Furthermore, since the present invention allows measurement data to be transmitted electronically, the measurement data can be incorporated into an irrigation control device or a comprehensive control system for plant cultivation and used as information for automatic soil moisture control.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the pressure-sensitive moisture sensor according to the present invention, FIG. 2 is a vertical cross-sectional view showing the internal structure, FIG. 3 is a plan view of FIG. 1, and FIGS. The figure is a conventional schematic configuration diagram. 10...Pipe, 11...Porous cup, 1
2...Tip cone, 13...Female thread, 14...Male thread, 15...Cover, 16...Piezoelectric element, 17
... Bellows, 18 ... Input/output terminal, 19 ... Lead wire, 20 ... Rainproof cover, 21 ... Pressure transmission tube, 22 ... Water inlet, 23 ... Water inlet tube, 24 ... Exhaust port, 25 ...Water injection, 26
...Exhaust exhaust.

Claims (1)

[Scope of utility model registration request] A moisture sensor that outputs an electrical signal corresponding to the moisture content of soil, etc., which includes a pipe of a predetermined length,
a porous cup made of a porous and highly rigid material detachably connected to the lower end of the pipe; a cover screwed to the upper end of the pipe; a piezoelectric element attached to the lower surface of the upper wall of the cover; A lead wire connected to the element to electrically transmit the output of the piezoelectric element, and a pressure sensor whose lower end is fixed to the bottom wall of the cover and whose upper end is held in contact with the piezoelectric element in order to transmit the water pressure in the pipe to the piezoelectric element. Motoko and
a pressure transmission tube that is connected to the pressure sensing element and whose tip faces into the pipe; an inlet that can be opened and closed near the upper end of the pipe; a water injection tube that extends from the inlet into the pipe; A pressure-sensitive moisture sensor characterized by comprising an exhaust port that is provided in the pipe above the injection port and can be opened and closed.