Field of application

The present invention relates to a sensor device for measuring height of water in a rice field, a lake, a river or the like. In particular, the invention relates to a sensor of the type above adapted to measure the height of water in fields used for cultivation where it is relevant to keep the flooding under few centimetres of water and, therefore also to optimize water savings in view of the climate changes, especially where said field are in areas affected by dryness.

The present invention also relates to a method for measuring a height of water in a rice field, a lake, a river or the like.

Prior art

It is known that water level sensors are used to control height of water is some fields used for cultivation, for instance where the alternate wetting and drying (AWD) flooded rice field irrigation method is used to cultivate rise. The water level sensors help farmers to adapt the AWD and to minimize the use of water resources; this is very important in areas where water is scarce but nowadays everywhere, given the changes in climate.

The most recent water level sensors are equipped with Cellular modems or LPWAN radios to communicate the water level remotely, and to allow the farmer to control an irrigation system remotely, in order to permanently flood with a depth of water varying, for instance, from 5 - 10 cm during the period after transplanting, until 2 weeks before harvest.

Although very appreciated, because providing almost constantly information on the water level, the sensors mentioned above are affected by some problems summarized here below.

As a first matter, the known sensors are not sufficiently precise, considered the field of application, wherein also an error of few centimetres may worsen the efficiency of the irrigation, causing an unnecessary activation of the irrigation system or delaying an activation, which is, to the contrary, necessary.

This problem affects almost all the technology used for the sensors, being they capacitive, i.e. adapted to derive water level by means of a difference between the dielectric coefficient of water and air, resistive, at ultrasounds, based on radar technology at high frequency, or piezoelectric. The error may be caused by intrinsic limitation of the measurement technique, also in connection with the hardware used, which is limited by economic contains, but also by the variable environmental condition affecting the measure, for instance changes in humidity, pressure, temperature, etc.

In an attempt to overcome at least part of the problems mentioned above, the most accurate sensors (and generally the most expensive) are equipped with calibrating means, to reduce influence of the variable in issue.

For instance, in some water sensor devices, the measurement is adjusted according to a top-down approach wherein a reference value is taken at the ground and the high of water is determined by comparing the reference value with a measurement value taken at the top level of water, for instance where a floating sensor is provided.

Unfortunately, in the mentioned attempt to improve precision, setting, management, and calibration of these sensors is complicated and may require intervening on the field, with specialized operators, as often as the condition changes, therefore also resulting in cost increases. This is not sustainable in some countries and undesired in general, also considering the number of sensors required to control wide areas.

The problem at the base of the present invention is to provide a device sensor adapted to improve precision of measurement of water level, at the same time not expensive, therefore usable in any cultivation and countries, allowing good water management practices, increasing yields, and therefore improving crop quality, conserving water, saving energy, decreasing fertilizer requirements, and reducing pollution, and substantially overcoming all the limitations that currently affects the known sensor devices.

Summary of the invention

The idea at the base of the present invention is that of determining the level (height) of water according to a bottom up approach not requiring calibration.

In particular, a reference value is taken as a pressure measurement at the time of measuring the level of water and a measurement value is taken as a pressure value at a bottom of a rice field, a lake, a river or any other area of interest, especially in association with cultivation, and the level of water is determined by means of the difference of the reference value and the measurement value.

More in particular, the measurement value is taken in an air chamber placed at said bottom by means of a first pressure sensor which is subject to both the pressure of the water and of the atmospheric air, therefore preventing that also the measurement value may be affected by variable environmental changes at the bottom, for instance due to temperature of water or debris and mud.

According to the idea of solution mentioned above, the technical problem at the base of the present disclosure is solved by a sensor device for measuring height of water in a rice field, a lake, a river or the like, including: a casing including an air chamber and a first pressure sensor adapted to measure pressure in the air chamber, a second pressure sensor, wherein the sensor device, in use, is fixed to a bottom of the rice field, lake or river, with the air chamber arranged to face water flowing at the bottom, and the second pressure sensor arranged outside water of the rice field, lake or river, in the air, wherein the sensor device is configured to determine the height of water based on a difference of pressure measured by the first pressure sensor in the air chamber and measured by the second pressure sensor in the air.

According to an embodiment, the first pressure sensor is an atmospheric pressure sensor. According to an embodiment, the second pressure sensor is an atmospheric pressure sensor.

Although the sensor device is disclosed with reference to a rice filed, a small river or lake, its usage is not limited thereto and may be considered in any other environment where level of water has to be measured for cultivation.

According to an embodiment, the sensor device includes a platform adapted to be fixed to the bottom of the field rise to prevent subsiding.

Preferably, the casing faces the platform and, in use, water flows between the air chamber and the platform.

In an embodiment, the device includes a pole whereto the platform, the casing and the second pressure sensor are attached. Preferably, a length of the pole is adjustable, for instance by means of a telescopic structure of the pole, to arrange the second pressure sensor outside water, depending on the height of the water from the bottom. More preferably, also the position of the casing on the pole may be adjusted, to determine the height of an area between the platform and the casing wherein the water may flow.

In an embodiment, the first pressure sensor is arranged on a circuit board and is encapsulated in a resin. According to an embodiment, the first pressure sensor is covered by a silicon wire protruding in the air chamber, by means of which the pressure is measured.

The circuit board is connected to a wire for power supply and data communication. For instance, the circuit board is fixed to an inner wall of the casing and includes a first surface arranged towards the bottom, in use, an opposite second surface, wherein the first pressure sensor is on the first surface.

Further advantages and features of the sensor device according to the present invention will be apparent in the description here below with reference to a drawing, given only for exemplificative purpose and not limiting the scope of protection of the present invention.

Brief description of the drawings

Figure 1 a schematic view of the sensor device according to the present invention.

Figure 2a is a side view of a particular of the sensor device of fig. 1. Figure 2b is a front view of the particular of fig. 2a.

Figure 2c is a lateral cross section of the particular of fig. 2a. Figure 3a is a picture of the sensor device in an embodiment.

Figure 3b is a particular of the picture of fig. 3a.

Detailed description

With reference to figure 1, it is schematically represented a sensor device 1 for measuring the level (height) of water according to the present invention, in particular for measuring the level of water in a rice field or the like, where controlling height of water is of primary importance for cultivation, for instance (but not exclusively) if an alternate wetting and drying (AWD) flooded rice field irrigation method is used to cultivate rise.

The sensor device 1 is particularly useful also for farmers needing information to minimize the use of water resources, by controlling for instance remotely, irrigation systems, in order to permanently flood the fields with a depth of water varying, for example, from 5 - 10 cm.

Actually, the sensor device 1 as herein disclosed is adapted for use in different cultivations and in other environments such as in small rivers or lakes, and everywhere water level has to be precisely monitored.

Figure 1 schematically represents one of such environments, for instance a rice field, having a bottom 31 submerged by a layer of water 30 with a height of around 10 cm for appropriate growth of rice. According to a method used to cultivate the rice (which is not scope of the present invention), the height of water 30 is controlled, for instance to remain within a predetermined threshold. Depending on the cultivation, the threshold may be different, but relevant is the fact that, in order to minimize the quantity of water used, it is in general preferred to activate the irrigation system as a function of the water level, for instance to keep the height of water always between 0 and 2000 mm.

According to the sensor device as disclosed, a first 3 and a second 5 pressure sensors are configured to be arranged, respectively, at the bottom 31 of the field, therefore in water 30, and outside water 30, i.e. in the air 20, above the surface 32 of water, at a predetermined distance therefrom. The first and second pressure sensors 3, 5 are both adapted to measure pressure of air, for instance up to 1.5 bar. In an embodiment, and preferably, the first and second pressure sensors 3, 5 are of same typology, as to the hardware components and software / firmware.

The first pressure sensor 3 is immerged in water by means of a casing 2 which is adapted to prevent direct contact between the first pressure sensor 3 and water. More particular, the casing 2 includes an external protective housing 13, within which the first pressure sensor 3 is enclosed.

Inside the casing 2, at a bottom of the housing 13, an air chamber 4 is delimited. In use, the air chamber 4 is arranged to face the water flowing between the bottom 31 of the (for instance rice) field and the casing 2, in a free space of height, for example, from 1 to 5 cm from the bottom 31 of the field. The height of the casing 2 from the bottom 31 is adjustable.

In an embodiment, a debris filter or a membrane 9 is placed at the bottom of the housing 13. In one embodiment, a flexible membrane 9 is arranged at the opening of the casing 2 and allows transfer of pressure exerted by water to to the air chamber 4. According to this embodiment, the air chamber 4 is closed by the membrane 9. However, different embodiments not provided with a flexible membrane 9 are also covered by the present invention. For instance, according to an embodiment, the opening of the casing 2 is free and air is trapped in the air chamber 4 by water between the bottom 31 and the air chamber

4.

The water so arranged pushes air towards the first pressure sensor 3.

Preferably, the first pressure sensor 3 is not placed directly in the air chamber 4 but in a second chamber, on top of the air chamber 4, i.e. more distant from the bottom 31 of the field, in use. In an embodiment, the second chamber is filled with an encapsulation resin 12, protecting the first pressure sensor 3. In another embodiment, the second chamber is empty and an encapsulation resin is arranged only onto the first pressure sensor 3. A probe 11, preferably in the form of a tube, has one end attached on the first pressure sensor 3 in the second chamber (in the encapsulation layer 12) and an opposite end in the air chamber 4. Pressure exerted by the column of water on the field and the pressure exerted by the atmosphere above the surface 32 of water, is transmitted by means of the probe 11 to the first pressure sensor 3. The probe may be, for instance, a tube of silicon. Preferably, the size of the silicon tube is same of a size of a cross section of a first surface of the first pressure sensor 3. Air flows from and to the air chamber 4 to the probe 11.

An opposite side of the first pressure sensor 3 is attached to a circuit board 8, which is preferably enclosed in the second chamber of the housing 13 and embedded by the encapsulation resin 12. The circuit board 8 is attached to a (plurality of) wire(s) 10 providing power supply and, preferably, data communication. One end of the wire 10, opposite to the end attached to the circuit board 8, may be connected to a reader device. Nothing prevents wireless communication of data, is which case the circuit board 8 may be provided with wireless transmission means and the wire may be a power supply cable only. The wireless transmission means may eventually be provided on another circuit board, arranged closer to the second pressure sensor 5 (for instance on a pole 7 of the device, as disclosed hereafter). As well, for some application, the circuit board 8 may be powered by a battery, in case a rechargeable battery, for instance rechargeable by solar power. A platform 6 is provided to support the casing 2 and to prevent that debris or mud interfere between the bottom of the (for instance rice) field and the air chamber 4. Preferably, the platform 6 has an area greater that a cross area of the casing 2 and the casing 2 (the air chamber 4) directly face the platform 6, for instance at a distance of 1 to 10 cm from the platform 6. Such a distance may be adjusted.

A pole 7 is attached to the platform 6 and supports the casing 2, preferably by means of adjustable coupling. The adjustable coupling includes for instance a slider, attached to the casing 2 and adapted to slide in a guide of the pole 7, and fastening means to block the slider (and the casing 2) at a desired position on the pole 7, corresponding to a desired height from the bottom 31.

Also, the position of the second pressure sensor 5 is adjustable on the pole 7, in particular to adjust the sensor device 1 depending on the maximum height of the water on the field. For instance, in case the maximum height is expected to be 2000 mm, the pole 7 may have a length of around 2500 mm and the second pressure sensor 5 may be fastened to the pole 7 at a distance of around 2200 mm from the bottom 31.

In one embodiment, also the second pressure sensor 5 is attached to the pole 7 by means of a slider/guide coupling, and by means of fastening means. In another embodiment, the second pressure sensor 5 is fixed at a predetermined position on a portion of the pole 7 which is however slidable with respect to another portion of the pole 7, for instance telescopic, in order to adjust the distance of the second pressure sensor 5 from the bottom 31.

Advantageously, the sensor device according to the present invention allows measuring precisely the height of the water level, with no calibration, and does not suffer from changes in the environmental condition, such as humidity, pressure or temperature changes. Indeed, a processor is configured to receive the pressure values measured at a time from, respectively, the first 3 and the second 5 pressure sensors. Preferably, the processor is embedded in a device on board of which also the second pressure sensor 5 is arranged. In another embodiment, the processor is associated to another device, for instance at the first pressure sensor side.

These pressure values are affected at that time by same environmental condition and therefore not adjustment is required. The processor is configured to determine the height of water on the base of the difference between the pressure values. In other embodiments, the sensor device 1 communicates only the pressure values sensed by the first and second pressure sensors, and the height of water is processed by a processor in a remote device, in communication with the sensor device 1.

The sensor device 1 is cheap and very easy to install. In this respect, the casing 4 may be is substantially embedded in a housing having the form factor of a power socked, and is attacked to a flexible cable, actually similar in size to an electric cable to which power socket are generally attached. The pole and the platform may be arranged on the field using material at hand. Also, the connection between the pole and the casing 2 may be realized using material at hand. Accordingly, a system for measuring a height of water using the sensor device of the present invention may be set very easily, with low cost and without any specialized personnel.

A method for manufacturing a sensor device for measuring height of water in a rice field, a lake, a river or the like, is briefly explained hereafter in one embodiment thereof.

A first pressure sensor 3 is coupled to a casing 2 to measure pressure. In particular, the step of coupling the first pressure sensor 3 to the casing 2 comprises attaching the first pressure sensor 3 to a circuit board 8, preferably a circuit board 8 including one or more through holes and a planar surface supporting the sensor 3.

In one embodiment, a gel is applied on the first pressure sensor 3 and at least on an area of the circuit board 8 surrounding the sensor 3.

Preferably, a probe 11 or tube, more preferably a silicon tube 11, for instance with a size substantially corresponding to a size of the first pressure sensor 3, is attached to the sensor 3, leaving the sensor 3 in contact with air in the tube. The silicon tube 11 forms a sort of air conduct towards the first pressure sensor 3, so as the first pressure sensor 3 is in air communication with air outside the tube 11. The tube 11 may be interlocked with an upper portion of the sensor 3.

The circuit board 8 and the first pressure sensor 3 are inserted into the casing 2, through an opening thereof.

Preferably, at least part of the casing 2 is filled with an encapsulation resin 12, introduced in the casing 2 through the opening. The resin 12 pass through the thorough holes in the circuit board 8, and therefore fills a portion of the casing 2 between a base of the casing 2 and the circuit board 8. The resin 12 may fill also a portion above the circuit board 8.

At least a portion of the casing 2 above the circuit board 8 is empty. The opening of the tube 11 is in the empty portion of the casing 2.

The casing 2 is attached to a pole 7 having a platform 6, with the opening of the casing 2 toward the platform 6 and the base of the casing 2 towards the upper portion of the pole 7.

Wire 10 connected to the circuit board pass through the casing 2, in particular through the base thereof, and are connected to an external device.

A second pressure sensor 5 is preferably attached to the pole 7, to read a pressure value outside the rice field, the lake, the river, i.e. in the air.

In use, the pole 7 is installed in rice field, lake or river so as (at least part of) the air arranged in the air chamber 4 and/or tube 11 remains trapped between the first pressure sensor 3 and the water in the rice field, lake or a river, in contact with the first pressure sensor 3.

The sensor device 1 is than used to determine the height of water based on a difference of pressure measured by the first pressure sensor 3 in the air chamber and measured by the second pressure sensor 5 in the air.

In particular, the height of water may be measured by arranging the sensor device 1 to the bottom 31 of the rice field, lake or river, with the casing 2 in water, and in particular arranging towards the bottom 31, inside the air chamber 4, an opening of the tube 11 having an opposed opening attached on the first pressure sensor 3, and therefore leaving the first pressure sensor 2 farther away from the bottom 31 with respect to the opening of the tube 11, to measure air pushed in the tube by the water.