GB2544497A

GB2544497A - Manifold moisture sensor

Info

Publication number: GB2544497A
Application number: GB1520284.9A
Authority: GB
Inventors: Bosnak Matevz
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-11-18
Filing date: 2015-11-18
Publication date: 2017-05-24
Also published as: GB201520284D0

Abstract

A soil moisture sensor comprises a processor 1 and a moisture sensing area 5. The sensing area contains a plurality of individual sensors 2, 3 and also an averaging sensor 7 to give a value over the length of the sensor. The sensors may be arranged in a vertical array so that when in use they may detect moisture levels at various discrete levels in the soil strata (Figure 2, item 10). The device may be mains 4 or battery powered. The sensors may be capacitive in nature and the array may be protected against abrasion and corrosion. The device may be equipped with a processing unit (19, Fig 2) that analyses the results from each sensor. The processing unit may calculate average values or may determine aggregate or weighted moisture levels, where the value may be biased to reflect moisture values proximate to the root structure of the plant. The sensor may send signals to a remote monitoring station which may be integrated with an irrigation system. The device is intended to reduce overwatering but also aims to ensure that the root structure is adequately watered.

Description

BACKGROUND OF THE INVENTION [0009] The weighted average allows the reading of r„„„„ _ . , ,. , ,, each sensing element to be ‘weighted’ differently, [0001] Optimal growth of the various agricultural . . . . ., ., . ., , , ,,, .,, giving more priority to soil moisture in the region of the crops and other cultured plants requires the control over f , , ,.,. , ,, plants roots. the plant environment, which is most frequently done .. ·,··,, ,· . , . ., ... . , . . [0010] Moreover, individual sensor readings can be in the form of the artificial irrigation. , .... . ...... ,., . , . , . extracted over digital communication interface and [0002] Plants absorb most of the water from the moist , . , , . ,,,., ., , , , , .... examined in order to detect unfavourable high- soil through the roots and transport it into the other . ,. ... _ , . . ™ . .,-, ,, moisture-gradient conditions. Such information can parts. Therefore, it is essential for the plant s roots to ,, .,, ,., ,, , .,, . , then be communicated to the operator, which can absorb enough water for the plant to survive and grow, ,.,, , .,, ,, decide to take proper counter-measures. but overwatermg the plant can cause problems too. r...., _ , , . , . , . . . , . . , , [0011] The manifold moisture sensor device is [0003] Through irrigation, the water is introduced at ,., , . . , , , . , . ,, designed to convey the measurement information in the sou surface and physical soil properties control the , ,, ,. . , . ,, . , , . , , . , . , „ analog and/or digital format, allowing the device to be absorption and vertical transport of the water. Porous , . . ... .,.,,, „ . used in various applications. Integrated processing unit soil seemingly absorbs water really fast, but does not ,, , , ,.,. , , . , can also be used to produce control signals for external accumulate it. The highly compacted soil surface on the ... . , ,., , , , . ,. , ., , . irrigation system, further reducing the system costs and other hand may indicate a saturated soil on the surface, ,, . ,.. „ , , , ., , . . allowing a very compact solution for small scale but the soil under the thin moist surface region stays ... applications.

r,, τ j .., . [0012] In terms of prior art, Pat. Nr. US 4801865 A

[0004] In order to optimize the amount of water . , . , ., ,., ., . . . introduces a moisture probe with multiple resistive required for the irrigation, soil moisture sensing is , . .,, ,, . , ° , probes in contact with the medium. Since conductivity employed - most frequently, electric impedance of the . ,, .. . . ,., .. ., . , , .,. ,. , ... „ . properties of the medium depend on multiple medium sou is used as the indicator of its humidity. Sensing . ,,, , , , . , , , . ,. ., , properties and the electrodes themselves are exposed to element is therefore put into direct contact with the ,.,, . , , ., ,, ,. ,, ,. , . chemical changes due to galvanic effects, the metered sou and the reading of the sensed impedance is . . . , ,.., , . , ., . , conductive moisture sensors can not be employed in the converted into the sou moisture value. _ , ., ,,, ,. . r... , . , ., field of agriculture tor the long-term applications.

[0005] Such sou moisture meters employ a single ,. . . , ,, ,. , , ., [0013] By limiting the measurements of the sensing element and the average reading of the sou ,. , , ,.. . , . . ° . , , ,.,,,, , , , medium s complex electric impedance to the imaginary moisture is therefore obtained. Although such approach ,,. ... - , ,, . , , ,, · · , ., part only (capacitance and inductance), one can works well in homogenous and well maintained sou, ,.. , . , ., ,, , ,. , ., , eliminate the requirement ot exposed probes and solve the readings become very inaccurate in large scale ,, . , ... . ,.,. ,. . , .,, ., . , ., the long-term sensor viability issue, as was claimed in

application, where soil physical properties change with ^ pat Nj. us 5g59536 A the depth. Most notably, the decrease in surface porosity will produce large gradients in the soil moisture between the surface and deeper regions, where the plant’s roots are and where the water is in fact required. During the irrigation of such soil, simple soil moisture sensors would indicate average soil moisture, which may lead to oversaturation of the surface with water and under-watered soil in the root space.

SUMMARY OF THE INVENTION

[0006] The scope of the invention is a manifold moisture sensor that is comprised of a plurality of individual moisture sensor elements. The device is designed for the installation into the target medium in such a way that the sensing area of the device is in direct contact with the medium, whose moisture is to be measured.

[0007] Each individual sensor element is capable of measuring the medium moisture content in the vicinity of the clement and forward this information to the processing unit.

[0008] The processing unit of the device takes care of sampling individual sensor elements and aggregating the values. Besides outputting individual sensor readings, the weighted average of these readings can be calculated and outputted. BRIEF DESCRIPTION OF THE DRAWINGS mogoce najti.. The processing part of the device 1 can be left above the medium surface 8 or be buried under [0014] The object of the invention will be explained ,. ., ..... , , . ,, . ... .. . [0023] The resulting measurements of the individual in the following on the basis of the accompanying , „ - ,,,,. . sensor elements 2, 3 correspond to local relative

Th Γ t f dr ' moisture content in the vicinities of each element 10 , ,, . s ' , , . with the resulting measurement of an optional sensing

Fig. 1: Illustration of the sensor device parts. , , _ ,. . , ® , ,. ,. , , . . , element 7 corresponding to an average moisture content

Fig. 2: Application of the sensor device for the ,. , . . ., _ ° ., ., of the medium the sensing area 5 is in contact with. The measurement of the soil moisture. .,. ,,. ., _ . .., , . sensor is therefore capable of measuring the average

Fig. 3: Communication options for the sensor device. . . .. , . , ., , ® , T„ .,., ., moisture content of discrete layers in the soil and

Fig. 4: Illustration of a logical structure of the sensor ,, ,°. overall average moisture content, device [0024] The essential part of the sensor is a central DETAILED DESCRIPTION OF THE INVENTION processing unit 19 that controls the input stage 17, connected with each sensing element 15 (depicted as 2, [0015] The innovation relates to a moisture sensor 3> 7 in Fig. j) by a means of signal lines 16. The central based on a manifold of individual moisture sensor processing unit also handles the scheduling of the elements, each capable of sensing the average moisture measurements, processing of the results and provides content of the environment, that is in close proximity to results to connected devices. that sensor element. [()()251 The measurements of each individual sensor [0016] The claimed sensor device comprises of two elements 15 are processed based on the configuration distinct parts - a moisture sensing area part 5 with that is stored in thc device’s non-volatile memory, individual sensing elements 2, 3, 7 and the capturing allowing the user of the device to reconfigure the device and processing part 1. The device can be powered via a functionality based on the soil type, plant’s root depth, power and communication cord 4 or using the internal communication interface options etc. battery power supply. [0026] ln order to address various installation [0017] Individual sensing elements 2,3,7 located on optjons, the sensor supports different communication the moisture sensing area 5 of the claimed device optjons, as depicted in Fig. 3, divided into three measure the electrical impedance of the surrounding categories· medium, that changes with the relative volumetric a wired (connection 11 used for power and water content in that medium. communication), [0018] The electrical impedance of the medium can b wired with wireless (connection 12 used for be represented with a real (resistance) and a complex power and/or communication with additional (capacitance and inductance) parts. Since the wireless interface 13 for communication) and measurement of the real part (resistance) requires c. wireless only (using alternate power supply, such conducting a current through the medium between a as batterieSi and using wireless communication), pair of electrodes, that is detrimental to both the [0027] Tllc output control 23 communication electrodes and medium properties, individual sensor interface 21 and power interface 24 are depicted as one elements of the claimed device implement the sub-system in Fig. 4 indicating that all can share the capacitive approach to measuring the medium s wired interface 22 allowing that interface to be used for impedance. power, communication and output control.

[0019] Individual sensing elements 2, 3 form planar [0028] The output control 23 allows the device to capacitors with the shared common electrode 6. The control an extemal load (watering pump, watering common electrode is therefore positioned along the vaive etc } based on currently measured value of soil whole length of the sensing area 5, with the sensing moisture, eliminating the need of additional external elements stacked one next to each other, as illustrated devices to control thc watering process, in Fig. 1.

[00201 The sensor device optionally implements an averaging sensing element 7 that senses the average moisture along the whole sensing area 5.

[0021] The sensing area 5 is protected from the direct contact with thc soil by a means of a protective layer that is resistant to abrasion and corrosion. This protective layer is made out of a non-conductive material.

[0022] The claimed sensor is designed to be installed in the target medium in such a way that the sensing area 5 is put into the direct contact with the target medium 9, as depicted in Napaka! Vira sklicevanja ni bilo

Claims

multi-functional interface that can be configured to operation with digital What is claimed is: communication or analog output that can

1. A device for measuring the moisture content adjust the function according to the user’s in multiple discrete areas of a bulk medium preference and configuration, (e.g. soil), the device comprising of: a combination of above; a sensing area comprising

3. A method of determining the soil moisture rigid elongated flat supporting body with gradient from measurements of the device spade shape on one end and attachment to from claim 1 with a sensor elements manifold, control electronics on the other end, This method can be used to classify the state of the surrounding medium, allowing the plurality (more than 3) of electrodes of identification of compacted soil by comparing capacitive sensing elements, the: soil moisture gradients over the sensor surface protective layer of non-conductive corrosion and abrasion resistant material; control electronics comprising 4 Measurement and calculation of a weighted input stage for converting the reactance avcraSe of moisture content over the sensinS . ,, , c ... . area of the device from claim 1. (mostly capacitance) of the sensing elements into the electrical signal that can be directly processed by a processing unit,

5. Device from claim 1 that functions also as a processing unit that controls the input programmable logic controller allowing the stage, processes its signals into a final user to controi watering process based on result, controls the output stage and sensor reading, schedules, custom logic handles the communication, operations, interfacing with other devices etc. output control, communication interface.

2. A device from claim 1 that supports various communication options, such as digital communication interface that is able to transfer digital data (measurement value and/or configuration) in one or both directions, analog output that allows the device from claim 1 to output an analog voltage corresponding to a measured value, digital output that can either signal the logical state of the measured value (lower/higher than the threshold), provide a pulse-width-modulated signal, which changes signal duty cycle corresponding to a measured value or a load control output that is used to control an external load, wireless (including NFC) that enables the device from claim 1 to transfer the configuration and/or measurement value wirelessly,