Description:TECHNICAL FIELD
[0001] The present disclosure relates to the field of data sensing and collection, and digital agriculture. More precisely, the present system and method is related to measurement of soil water potential (Water Tension) from multiple sensors.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present disclosure. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed disclosure, or that any publication specifically or implicitly referenced is prior art.
[0003] Soil water tension (SWT) or Soil Water Potential (SWP) is the force necessary for plant roots to extract water from the soil, as it reflects the soil moisture status and can be used to determine how much water is available in the soil for the plant . The higher the tension, the drier the soil. A sensor can be used to measure the actual soil water tension by extracting water from the soil. There are resistive based sensors in the prior art with an operating principle that change in water content in the soil results in a change in resistance. And the simplest way to measure resistance value using a microcontroller is to create a voltage divider circuit and read the change in voltage and translate it to its equivalent resistance.
[0004] Soil moisture sensors, like the Irrometer Watermark 200SS, measures electrical resistance inside of a granular matrix to determine soil water tension. Traditionally, it has been achieved by creating a voltage divider circuit to measure changes in voltage, which are then translated into resistance values. However, using Direct Current (DC) as the power source in such circuits can lead to corrosion of the sensor electrodes due to electrolysis. The use of DC power sources in soil moisture sensor circuits leads to electrode corrosion, significantly reducing the sensor's lifespan. The limitation restricts the effectiveness of soil water potential monitoring systems, especially in long-term applications where durability is essential.
[0005] One way to reduce the corrosion and increase the sensor life is to power the sensor with Alternating Current (AC) instead of DC. A sensor with AC current can minimize potential for detrimental reactions at the electrode-soil interface, enhancing the long-term reliability and accuracy of soil water tension measurements.
[0006] The reference circuits provided by companies like Irrometer for resistive-based soil moisture sensors are often complex and may not effectively address the issue of electrode corrosion. Additionally, there is a lack of readily available circuits in the market that can continuously read from multiple sensors using a single microcontroller, further complicating the implementation of multi-sensor soil moisture monitoring systems. In summary, existing solutions for reading from multiple soil moisture sensors using DC-based circuits suffer from electrode corrosion issues, leading to limited sensor lifespan and complexity in circuit design.
[0007] Therefore, there is a need for a device with a special circuit with AC current and an operational method thereof that is resistant to corrosion, can operate multiple sensors at once and can be used to measure soil water tension for extended durations.

OBJECTS OF DISCLOSURE
[0008] Some of the objects of the present disclosure, that at least one embodiment herein satisfy are as listed herein below.
[0009] An object of the present disclosure is to develop a soil moisture monitoring system (100) that mitigates electrode corrosion issues, thereby extending the lifespan of resistive-based sensors like the Irrometer Watermark 200SS.
[0010] An object of the present disclosure is to create a simplified and efficient circuit design that eliminates the use of DC voltage entering the sensor, reducing the risk of electrode corrosion due to electrolysis and enhancing the reliability of soil moisture measurements and soil water potential calculations.
[0011] Another object of the present disclosure is to enable the system to read data from up to 4 sensors simultaneously, providing comprehensive soil moisture information across different locations or depths within the soil profile.
[0012] Another object of the present disclosure is to enable the system to read data from any resistive based sensors where change in the sensor resistance due to change in the environment parameter being sensed results in change in frequency output from the 555 timer IC and the relevant environment parameter can be mapped based on the obtained frequency.

SUMMARY
[0013] Within the scope of this application, it is expressly envisaged that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.
[0014] In an aspect of the present disclosure, it describes a soil moisture monitoring system consisting of a low power and high frequency 555 timer circuit operating in the astable mode which converts the sensor resistance to equivalent frequency signal. The 555 timer IC provides pseudo-AC excitation to safeguard the sensors from corrosion. A datalogger connected to the 555 timer and is capable of converting the received frequency signals to Centi Bar (CB) values using proprietary equations.
[0015] In another aspect of the present disclosure, the method of the present disclosure includes connecting up to four resistive sensors through a multiplexer to the 555 timer IC. The method further comprises connecting the multiplexer and the 555 timer IC to a datalogger configured for soil moisture monitoring, which receives the frequency signals and converts it to centibar (CB) values using proprietary equations within the datalogger’s firmware. The method also includes providing pseudo-AC excitation to the sensors through the 555 timer to safeguard against degradation and select the multiplexer channels to shift through the 4 sensors connected to the 4 channels thereby providing complete galvanic isolation to each sensor from one another. This ensures there is no interference between sensors while reading the individual sensor values. The multiplexer and 555 timer can also be switched off completely there by cutting off power to the sensor and thus extending its life in the field for a greater duration.
[0016] Various objects, features, aspects, and advantages of the inventive subject matter
will become apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF DRAWINGS
[0017] The specifications of the present disclosure are accompanied with drawings of the system and method to aid in better understanding of the said disclosure. The drawings are in no way limitations of the present disclosure, rather are meant to illustrate the ideal embodiments of said disclosure.
[0018] In the figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label with a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.
[0019] FIG. 1 illustrates a block diagram of the system for soil moisture monitoring, in accordance with an embodiment of the present disclosure.
[0020] FIG. 2 illustrates a circuit diagram for the 555-timer based instrumentation circuit and multiplexer used in the system, in accordance with an embodiment of the present disclosure.
[0021] FIG. 3 illustrates an illustration of an exemplary method for soil moisture monitoring, in accordance with an embodiment of the present disclosure.
[0022] FIG. 4 illustrates the overall IoT infrastructure of the system, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0023] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such details as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0024] In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to one skilled in the art that embodiments of the present disclosure may be practiced without some of the specific details.
[0025] If the specification states a component or feature “may”,”can”,”could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have that characteristic.
[0026] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0027] The present disclosure relates to the field of data sensing and collection, and digital agriculture. More precisely, the present system and method is related to measurement of soil water tension from multiple sensors.
[0028] FIG. 1 illustrates a block diagram of the system for soil moisture monitoring and obtaining the soil moisture potential in CB, in accordance with an embodiment of the present disclosure.
[0029] Referring to FIG. 1, a soil moisture monitoring system 100 is disclosed comprising a low power high frequency 555 timer (a CMOS 555 timer IC having Fmax of 1MHz to 3MHz) 112 that is configured to work in the astable mode where the 555 timer acts as an oscillator, which means it produces a continuous square wave output with a frequency whose value is determined by the values of resistors and capacitors in the circuit. By making one of the resistors variable (the resistive sensor), you can use it to control the frequency of the output signal. A multiplexer 102 is used to connect up to 4 resistive sensors 106 to the 555 timer IC. Because the multiplexer switches between the individual sensor paths, there is complete galvanic isolation from one sensor to another and thus eliminating interference from other sensors as well as the ground; a datalogger 104 for soil moisture monitoring, wherein the datalogger 104 is able to control the power to the 555 timer IC 112 and the 4 channel dual multiplexer 102 and also perform channel selection of the multiplexer 102, and wherein the datalogger 104 is able to read the frequency output of the 555 timer IC and converts the frequency value to the soil water potential values in centibar (CB) using a plurality of proprietary equations; a conversion module 108 to receive the frequency signals and convert them to one or more centibar values using the plurality of proprietary equations derived by the datalogger 104; and the 555 timer IC 112 provides an Alternating Current (AC) excitation to the connected four resistive sensors 106, wherein the AC excitation safeguards the four resistive sensors 106 against degradation.
[0030] Awareness of soil water content is not sufficient to take informed decisions on when to irrigate and how much to irrigate. The soil water content (or soil moisture content) can be 100%, but how much of it is actually available for the plant root to absorb will depend on the soil type, soil granule size, etc. It is pertinent to determine and accurately measure the efforts required by the roots of the plant to displace the water from the soil and absorb it. This effort or force used by the plant root is called “Soil Water Potential” and is represented in Centibars (CB) or Kilopascals (Kpa). (1 Kpa = 1 CB). The soil water potential depends greatly on the soil texture and structure. A range of values for different types of soil including sand, loam, and clay.
[0031] An awareness of the soil water potential allows any need for irrigation to be quantified in advance of a crop showing signs of distress. Knowing the soil water potential status enables highly efficient irrigation, providing the water as and when required, and eliminating the wasteful use of water when irrigation is not needed. The terms soil water potential and soil moisture content are used interchangeably in the present disclosure.
[0032] In an embodiment, the multiplexer 102 serves as a switching system that connects up to 4 sensors 106 to the 555 timer IC 112. It sequentially connects each sensor channel to the master channel and the sensor path gets connected to the 555-timer instrumentation circuit which produces equivalent frequency proportional to the resistance of the sensor. By using a multiplexer 102, the system 100 efficiently handles data from multiple sensors, allowing comprehensive soil moisture monitoring. The datalogger 104 is able to switch through the slave channels of the multiplexer 102 based on the logic state of the select line S0 and S1 of the multiplexer 102 controlled by the datalogger 104. The datalogger 104 is connected to the 555-instrumentation circuit 112 and receives the frequency signals from it. The datalogger 104 is equipped with circuitry and firmware/software to read the frequency of the output signal from the 555-instrumentation circuit and convert the frequency values. The datalogger 104 also utilizes proprietary equations to perform the frequency to equivalent soil water potential values in centibars using proprietary equations, ensuring accurate and reliable soil water potential measurements.
[0033] In an embodiment, each of the four resistive sensors (Irrometer watermark 200ss) (106-1, 106-2, 106-3, and 106-4, collectively referred to as sensors 106 or sensor 106, hereinafter) can have two output wires or terminals representing the resistance measurement. The wires can be connected to specific input channels of the multiplexer 102. The output wires from each sensor 106 can be connected to the input channels of the multiplexer 102. Each sensor 106 can be typically assigned to a dedicated input channel on the multiplexer 102. For example, Sensor 1 might be connected to Input Channel 1, Sensor 2 to Input Channel 2, and so on. The multiplexer 102 requires control signals to select the desired input channel and route the corresponding sensor signal to its output. The control signals may be typically provided by the datalogger 114 or controller and specify which sensor's signal is currently being read. Based on the control signals received, the multiplexer 102 selects the appropriate input channel and routes the signal from the corresponding sensor to its output, which allows the datalogger 114 or controller to sequentially read the signals from each sensor without having to physically disconnect and reconnect them. This also provides complete galvanic isolation between each of the sensors 106.
[0034] In an embodiment, the datalogger 104 can typically refer to a device that records data over time or in relation to location, either with a built-in instrument or sensor or via external instruments and sensors. The datalogger 104 may have internet connectivity capabilities, Bluetooth / BLE connectivity capabilities, LoRa connectivity capabilities, and may incorporate IoT functionality, to transmit data wirelessly over the internet to cloud-based servers or other devices for remote monitoring, analysis, and control. The IoT-enabled datalogger 104 may provide real-time data access and remote configurations. In summary, while a datalogger 104 can be equipped with IoT capabilities, not all dataloggers are inherently IoT devices. It ultimately depends on the design and features of the specific data logging device.
[0035] In an embodiment, the conversion module 108 is part of the firmware running in the datalogger 104 that receives the frequency value as an input and uses proprietary equations and processes them to derive centibar values, which represent soil water tension. The derived values match with the hand-held soil water tension meter of Irrometer. It utilizes the proprietary equations derived by the datalogger 104 to convert the frequency signals into meaningful soil moisture data.
[0036] In an embodiment, the instrumentation circuit 112 typically does not directly control the conversion module 108. Instead, it facilitates communication between the modules and other components of the system 100, such as the microcontroller or datalogger 104.
[0037] In an embodiment, the instrumentation circuit 112 may also incorporate isolation techniques such as optocouplers, transformers, or digital isolators to electrically separate the sensor inputs for galvanic isolation between all four sensors 106. The instrumentation circuit 112 may also allow signals to pass between the sensors and the datalogger 114 or controller without creating a direct electrical connection.
[0038] In an embodiment, the instrumentation circuit 112 generates control signals based on instructions from the system controller (e.g., microcontroller or datalogger). The control signals specify the desired input channel to be selected on the multiplexer 102. The control signals can be routed to the appropriate input pins of the multiplexer 102. Each input pin corresponds to a specific input channel of the multiplexer. Upon receiving the control signals, the multiplexer 102 activates the corresponding input channel, connecting it to the output channel. It allows the sensor signal from the selected input channel to pass through the multiplexer 102 and be processed by the downstream components of the instrumentation circuit.
[0039] In an embodiment, in the multiplexer, the “MUX Enable” pin is used to enable and disable the multiplexer. This is used to further limit the current and voltage going into the sensor when in sleep mode. This also helps in extending the sensor life by limiting the power to the sensor 106.
[0040] In an embodiment, the multiplexer 102 used is the 74HC7052D. This can be used to extend the number of sensors connected to the 555 timer IC. The multiplexer 102 has four dual input channels labelled Y0 (1Y0, 2Y0), Y1 (1Y1, 2Y1), Y2 (1Y2, 2Y2) and Y3 (1Y3, 2Y3). Additionally, there is an output dual channel Z (1Z and 2Z). This output dual channel Z is connected as input to the 555 timer IC. The IC employs a switching mechanism controlled by select pins (S0 and S1) to determine which dual input channel is connected to the output. By varying the logic states of the select pins, different input channels can be sequentially selected and connected to the output. Example: is logic state of S0 and S1 and 0 and 0, then the channel Y1 is selected and 1Y0 gets connected to 1Z and 2Y0 gets connected to 2Z. The 74HC7052D is controlled digitally, with the select pins driven by digital logic signals (e.g., HIGH or LOW). The digital control allows for easy integration with microcontrollers or other digital control circuits.
[0041] The multiplexer IC can be designed to operate with standard CMOS logic levels and is compatible with a wide range of digital systems. It can operate over a wide voltage range, typically from 2V to 6V, making it suitable for use in various applications. The 74HC7052D typically comes in a standard integrated circuit package, such as the SOIC (Small Outline Integrated Circuit) package, which allows for easy soldering onto printed circuit boards (PCBs). The 74HC7052D is commonly used in applications requiring signal multiplexing, such as data acquisition systems, communication systems, and instrumentation.
[0042] In an embodiment, the multiplexer 102 also features four dual input channels. This allows us to connect up to four sensors 106. Each input channel pair creates a path from the sensor to the 555 timer IC through the multiplexer output channel. The multiplexer 102 employs a switching mechanism to sequentially select and connect one of the input channels to the output channel, which is linked to the datalogger 104. The switching mechanism can be controlled electronically, either manually or automatically, to cycle through each sensor's 106 signal. When a specific sensor's 106 signal is selected, the multiplexer 102 routes it through to the output channel, ensuring that only one sensor's 106 signal is transmitted to the datalogger 104 at any given time. The sequential routing process allows the datalogger 104 to capture data from each sensor individually, enabling comprehensive monitoring of soil moisture levels.
[0043] The output channel of the multiplexer 102 is connected to the input of the 555 timer IC 112 which becomes a part of the instrumentation circuit and the output of the 555 timer IC 112 is connected to the input of the datalogger, ensuring seamless integration between the two sub systems. The 555 timer IC 112 generates frequency signal proportional to the sensor’s resistance value. The datalogger 104 receives the frequency signals from the instrumentation circuit 10X and processes them to convert the frequency values into equivalent centibar values (CB) based on proprietary equations. The operation of the multiplexer 102 is synchronized with the datalogger’s 104 data acquisition process to ensure accurate and synchronized measurements from all connected sensors 106. Control signals from the datalogger 104 or an external controller regulate the switching of input channels, controlling the sequencing of sensor data acquisition.
[0044] In an embodiment, the multiplexer 102 can display various configurations for interactions with the four resistive sensors. The multiplexer 102 can be configured to sequentially switch between the four resistive sensors connected to its input channels. The switching mechanism is controlled by a digital control unit in the datalogger, which sends signals to the multiplexer 102 to select each sensor 106 in a predetermined sequence. For example, the multiplexer 102 may start by selecting sensor 1, then switch to sensor 2, followed by sensor 3, and finally sensor 4. The sequential switching allows the datalogger 104 to capture data from each sensor individually, ensuring comprehensive monitoring of soil moisture levels across different locations or depths within the soil profile.
[0045] In another embodiment, the multiplexer 102 can be configured to prioritize certain sensors over others based on predefined criteria. For example, sensors located in critical areas of the soil profile may be given higher priority compared to sensors in less important areas. The multiplexer 102 can be programmed to prioritize data acquisition from these critical sensors whenever they are available. In case of conflicting requests for data from multiple sensors, the multiplexer 102 resolves the conflict based on the predefined priority scheme. The priority-based switching ensures that data from the most important sensors is captured promptly, facilitating timely decision-making in soil moisture management.
[0046] In an embodiment, the proprietary equations used to convert the frequency to centibar value encompass a comprehensive set of parameters and adjustments aimed at ensuring accurate and reliable soil moisture measurements. The values take into account various factors, enhancing the sensor's versatility and precision. There can be a parameter for soil type adjustment, wherein said parameter can accommodate different soil types exhibiting varying electrical conductivity, and the adjustment ensures that the sensor provides accurate readings across diverse soil compositions. Another parameter is for sensor geometry correction accounting for the physical geometry and arrangement of the sensor 106. The geometric design of the sensor 106 can influence how it interacts with the soil, and the coefficients help standardize measurements across different sensor configurations. Further, there are parameters for temperature compensation values for adjustments to account for variations in temperature. The temperature can impact the electrical conductivity of the soil, and temperature compensation coefficients ensure that the sensor’s 106 measurements remain accurate under varying temperature conditions. There can also be coefficients to address manufacturing tolerances and variations, which ensures consistency in measurements even when sensors 106 are produced with slight manufacturing differences. User-defined parameters can allow users to make personalized adjustments based on specific needs or conditions for users to tailor the sensor’s 106 performance to the unique characteristics of their application.
[0047] In an embodiment, the instrumentation circuit (200) uses a CMOS 555 IC line the LMC555 to convert the sensor’s 106 resistance value to equivalent frequency. The 555 IC Timer 112 requires resistors and capacitors to configure it to work in the astable multivibrator mode. The circuit operates in its direct feedback astable multivibrator mode, with a square wave on a totem pole output from pin 3 charging or discharging the 100nF MLCC timing capacitor through the network of fixed resistors in series/parallel with the sensor 106. The sensor 106 is connected to the 555 timer’s TRIGGER and OUTPUT pin through the multiplexer. The sensor 106 is essentially acting like a variable resistor connected across these two pins. There is also a pull up resistor R1 on the 555 IC DISCHARGE pin and a Capacitor C1 connected to ground on the 555 IC THRESHOLD pin. The frequency signals are generated on the DISCHARGE pin of the 555 IC 112 which is connected to the input GPIO of the microcontroller. The circuit additionally comprises two capacitors CS1 and CS2, which are used to ensure that no DC voltage component enters the sensor 106, a resistor RP parallel to the sensor and . The circuit can have a 3.3V supply and the output of the circuit can get connected to a microcontroller digital input pin.
[0048] In an embodiment, considering a theoretical working of the circuit, said circuit can be configured as an astable multivibrator, which means it produces a continuous square wave output with a frequency determined by the values of resistors and capacitors in the circuit. By making one of the resistors variable, it can be used to control the frequency of the output signal. In our case, the Irrometer 200SS sensor is the variable resistor. The formula that relates the resistors, capacitor and frequency is: f = 1.44/[(R1 + 2R2) x C1], where R1 = Fixed resistor in the circuit = 1KO, C1 = Fixed capacitor in the circuit = 100nF = 0.0000001F, and R2 = Sensor Watermark 200ss resistance in parallel with the 150KO, which is parallel to the system 100 of the present disclosure to ensure that if said system 100 is completely dry, the resistance value will not be infinite. (Based on parallel resistance equivalent value, 150KO in parallel with infinite resistance (open circuit) = 150KO). The 390O acts as a current limiting resistor to the sensor 106.
[0049] Based on the above theoretical working of the circuit, two extreme scenarios can be considered. 1. The system 100 is completely dry wherein the soil has no moisture content. Therefore, the resistance is infinite. Since there is the 150K resistance in parallel to the sensor, the equivalent resistor value will be 150K ohms. By adding it to the formula:
f = 1.44 / ((1K + (2*150K))* 0.0000001)
f = 1.44 / 0.0301 = 47.84 Hz
Hence, when the sensor is completely dry, the frequency output will be around 47.84 Hz.
[0050] In another embodiment, when the system 100 is replaced with a wire (short-circuit condition), the resistance is zero. . Since there is the 150K resistance in parallel to this, the equivalent resistor value will be 0 ohms. By adding it to the formula: f = 1.44 / ((1K + (2*0))* 0.0000001), f = 1.44 / 0.0001 = 14,000 Hz. Hence, when the sensor in system 100 is short-circuited, the frequency output will be around 14K Hz.
[0051] When the system 100 is completely wet (immersed in water), the resistance can never become zero. As per tests, it will be around 400 to 500 O and corresponds to a frequency of 7200 to 8000 Hz. The current through the sensing grid is AC. The system 100 can include non-polar ceramic capacitors that isolate the circuit from the sensor 106, to assure that the average current is AC and to forestall galvanic interactions in the soil environment. The output frequency is transmitted to the microcontroller 104 from the open collector DIS output pin. Normally a pullup resistor may be provided to give voltage transitions at the microcontroller 104.
[0052] In an embodiment, the datalogger 104 can be outfitted with one or more self-diagnostic capabilities aimed at promptly identifying any sensor malfunctions during data acquisition. The diagnostic features enable the system 100 to autonomously monitor sensor performance, detect irregularities or anomalies in the acquired data, and flag potential malfunctions or discrepancies. By continuously assessing sensor health and data integrity, the datalogger 104 can proactively identify issues such as sensor drift, signal noise, or electrode degradation, which may compromise the accuracy and reliability of soil moisture measurements. The self-diagnostic capabilities streamline maintenance and troubleshooting processes by providing real-time feedback on sensor status, facilitating timely interventions, and minimizing downtime. The proactive approach to sensor monitoring enhances system 100 reliability, prolongs sensor lifespan, and ensures consistent performance, thereby optimizing the overall effectiveness of the soil moisture monitoring system 100 in agricultural, environmental, and landscaping applications.
[0053] FIG. 2 illustrates a circuit diagram of the instrumentation circuit that consists of the 555 timer IC and the multiplexer 102 used in the system 100, in accordance with an embodiment of the present disclosure.
[0054] In an embodiment, the multiplexer 102 starts by selecting one of the resistive sensors connected to its input channels. Once selected, the multiplexer 102 routes the signal from the selected sensor to the output channel connected to the 555 timer IC 112 which then generates equivalent frequency signal that is ten fed into the microcontroller 104. The microcontroller 104 then reads the frequency signal using an input capture timer routing and then uses proprietary formula to convert the frequency to CB. After measuring the resistance value of the first sensor 106, the microcontroller toggles the select lines of the multiplexer 102 to switch to the next sensor in line and repeats the process. The sequential operation continues until data from all four sensors has been captured and processed by the microcontroller 104.
[0055] In an embodiment, the multiplexer enable pin is controlled by the microcontroller. The multiplexer 102 is enabled only at the time of sensor reading and then disabled. By disabling the multiplexer 102, there is galvanic isolation of power to the sensors. This ensures that there is no current leakage, thereby extending the life of the sensor.
[0056] In an embodiment, there is a 3.3V power regulator with an enable pin as well. The power to the 555 IC 112 and multiplexer 102 is controlled using the enable pin. The microcontroller enables the power only at the time of sensor reading. This ensures that there is no current leakage, thereby extending the life of the sensor.
[0057] In an embodiment, the system 100 may provide daisy-chaining capabilities for multiple multiplexers 102, allowing users to expand the number of sensors 106 that can be connected to a single datalogger 104 or measurement system 100. The feature enhances scalability and flexibility. The system 100 can also enable remote configuration of the multiplexer 102 settings through a communication interface, which allows users to adjust parameters such as scan rates or channel configurations without physically accessing the system 100. The system 100 may support various digital communication protocols (e.g., I2C, UART, SPI) to facilitate seamless integration with different microcontrollers, dataloggers, or measurement systems, which ensures compatibility in diverse sensor 106 network setups. The system 100 may also incorporate built-in calibration circuitry to automatically calibrate sensor 106 readings during operation. The feature helps maintain the accuracy and reliability of measurements over time, reducing the need for manual calibration.
[0058] In an embodiment, the datalogger 104 often includes a microcontroller, memory storage, communication interfaces, and a power supply. The microcontroller is the brain of the datalogger 104, responsible for controlling and coordinating various functions. It executes the embedded software or firmware that manages data acquisition, storage, and communication with the sensor 106 components. The datalogger 104 features onboard memory storage, such as flash memory or an SD card slot, to store collected data. The storage capacity is critical for retaining historical measurements, calibration values, and other relevant information. The datalogger 104 can incorporate communication interfaces for seamless interaction with external systems or networks. Common interfaces include USB, RS-232, RS-485, or wireless options like Bluetooth or Wi-Fi. The interfaces can enable data transfer, configuration adjustments, and real-time monitoring.
[0059] In an embodiment, the system 100 can include built-in data logging and storage capabilities for recording and archiving soil moisture data over extended periods. The datalogger 104 is equipped with non-volatile memory, such as flash memory or EEPROM (Electrically Erasable Programmable Read-Only Memory), to store measurement data locally. The system 100 automatically logs soil moisture readings at regular intervals and timestamps them for reference and analysis. Users can retrieve stored data from the datalogger 104 either locally via a USB connection or remotely through wireless communication. The data logging and storage feature ensures data integrity, facilitates historical trend analysis, and supports decision-making in agriculture, landscaping, and environmental management applications.
[0060] In an embodiment, the datalogger 104 can be equipped with a power supply system, which may include batteries, solar panels, or other energy sources depending on the application and deployment duration. Efficient power management is essential for prolonged field deployments. The datalogger 104 can be programmed to initiate and control the data collection process. The obtained electrical resistance values are then processed by the datalogger 104. The datalogger 104 can include algorithms for converting the measured electrical resistance values to soil water potential. The algorithms can utilize the calibration values supplied by the sensors to ensure accurate and calibrated soil moisture readings. To establish a temporal context for measurements, the datalogger 104 often includes a real-time clock (RTC) for time stamping. It allows users to correlate soil moisture data with specific time points, aiding in trend analysis and decision-making. The datalogger 104 may perform basic data analysis tasks onboard, such as calculating averages, trends, or identifying anomalies. Processed data is then logged into the memory storage for future retrieval or external analysis.
[0061] In an embodiment, the instrumentation circuit 112 does not measure the sensor’s 106 internal resistance directly. The sensor 106 resistance forms part of the instrumentation circuit (555 IC) which outputs an alternating signal whose frequency is a function of resistance. As the soil (and sensor) dries, the soil-water potential decreases (becomes more negative), and the sensor’s internal resistance increases. The increasing resistance causes the frequency of the output signal to decrease. The microcontroller program uses a timer input capture routine to measure the frequency of the alternating signal in terms of pulse width. As the signal alternates between periods of high and low voltage levels, the timer capture routine measures the length of time, or duration, in microseconds (us), of the high-voltage state. The pulse width measurement may then be used to calculate water potential. The sensor 106 outputs frequency in the range of around 50 Hz to 8000 Hz from wet to dry condition of the soil which gets converted to 0 to 200CB using proprietary equations.
[0062] Because the multiplexer 102 switches between the sensor 106 paths, there can be complete isolation from one sensor 106 to another and thus eliminating interference from other sensors 106 as well as the ground.
[0063] The proprietary equations used to convert frequency to CB is as follows:
CB = 0 for Hz > 6430
CB = 9 - (Hz - 4330) * 0.004286 for 4330 <= Hz <= 6430
CB = 15 - (Hz - 2820) * 0.003974 for 2820 <= Hz <= 4330
CB = 35 - (Hz - 1110) * 0.01170 for 1110 <= Hz <= 2820
CB = 55 - (Hz - 770) * 0.05884 for 770 <= Hz <= 1110
CB = 75 - (Hz - 600) * 0.1176 for 600 <= Hz <= 770
CB = 100 - (Hz - 485) * 0.2174 for 485 <= Hz <= 600
CB = 200 - (Hz - 293) * 0.5208 for 293 <= Hz <= 485
CB = 200 for Hz < 293
Table 1: Frequency to CB conversion
In the context of soil water potential, 1 centibar (CB) is equal to 1 kilopascal (kPa). This means that these two units are directly interchangeable when measuring soil water potential.
[0064] In an embodiment, an IoT connectivity sub system 114 can be connected to the datalogger to enable data transmission to other systems or to any cloud platform using 4G or 5G cellular modem. By enabling data exchange, real-time sensor values can be monitored remotely there by extending the capabilities of the system and enhancing user experience.
[0065] In an embodiment, a mobile application can be integrated with the system 100, allowing users to monitor soil water tension data, receive real-time alerts, and adjust settings remotely using smartphones. The mobile application can implement a secure user authentication module to ensure that only authorized users can access the system 100 data and control settings. The system 100 can also provide users with a visually intuitive dashboard displaying real-time soil water tension data including graphical representations, charts, and key metrics to offer a quick overview of current conditions. The mobile application can display historical trends and patterns of soil water tension, allowing users to track changes over time, which can help users make informed decisions about irrigation strategies. The user can also remotely adjust settings on the system 100 through the mobile app, including modifying irrigation schedules, changing alert thresholds, or adjusting other system 100 parameters.
[0066] In an embodiment, the system 100 includes a mapping feature for providing a geospatial visualization of soil moisture levels, presenting data in the context of the monitored area. Users can view a map on the user interface that represents different locations and their corresponding soil water tension values. Soil moisture levels can be typically represented using a color gradient on the map. Different colors indicate varying levels of soil water tension. For example, blue might represent higher moisture levels, while red or orange might indicate drier conditions. The mapping feature can be updated in real-time, reflecting the most recent soil moisture data collected by the system 100, which ensures that users have access to the latest information about soil conditions. Users can have the flexibility to define specific zones within the mapped area. The zones may correspond to different crop types, irrigation zones, or other relevant divisions. The users can also customize the mapping display based on these defined zones. Critical soil moisture thresholds can be highlighted on the map to draw attention to areas requiring immediate attention, which helps users identify regions that may need irrigation adjustments or further investigation. The mapping feature may allow users to compare current soil moisture levels with historical data. The comparison can help users identify trends, assess changes over time, and make more informed decisions about irrigation strategies.
[0067] In an embodiment, the soil moisture mapping feature can be designed to be accessible on mobile systems, allowing users to view maps, analyze data, and make decisions while in the field, which enhances the mobility and convenience of the monitoring system 100. The mapping interface may support layered information, allowing users to overlay soil moisture data with other relevant information, such as weather patterns, topography, or satellite imagery. The layered approach provides a comprehensive understanding of the factors influencing soil moisture. Users may also have the option to export mapping data for further analysis or share it with other stakeholders. The feature can support collaboration and communication among individuals involved in agricultural or environmental management. The mapping interface can be integrated with alert and notification systems. Users can receive alerts directly on the map when certain soil moisture conditions are met, enabling prompt response and intervention.
[0068] In an embodiment, the system 100 can have a modular design for effortless scalability by adding or removing sensors 106 based on the size and requirements of the monitored area. Users can expand the system 100 by incorporating additional modules to cover larger agricultural fields or environmental monitoring zones. The system 100 may include standardized connectors or interfaces that facilitate seamless communication and integration between sensor 106 units. The interconnectivity ensures that the sensors 106 work cohesively to provide a comprehensive view of soil moisture conditions. Despite the modularity, the system 100 may feature a centralized datalogger 104 that serves as the main control and communication hub. The datalogger 104 consolidates information from all sensor 106 units, enabling unified data collection, storage, and analysis. The centralization simplifies the management of the entire system 100. The system 100 may also incorporate a plug-and-play functionality, allowing users to easily add or remove sensor units 106 without complex installation procedures. It can feature streamlines system 100 expansion or adjustment, making it accessible to users with varying levels of technical expertise. Configuration settings for each sensor 106 can be user-friendly, allowing users to adjust parameters easily for the user to fine-tune the system 100 according to specific needs, such as changing the sampling frequency or setting customized thresholds.
[0069] In an embodiment, the datalogger 104 can store the converted soil water potential measurements for future reference and analysis. The storage may be in the form of a database or log file, enabling the creation of historical records. Users can analyze the stored data to understand patterns, trends, and variations in soil moisture levels. The analysis may reveal insights into the impact of environmental factors on soil water potential. The datalogger’s 104 output provides valuable information for decision-making in agriculture, irrigation, and environmental monitoring.
[0070] FIG. 3 illustrates an illustration of an exemplary method 300 for soil moisture monitoring, in accordance with an embodiment of the present disclosure.
[0071] Referring to FIG. 3, a method 300 for implementing the system 100 to measure soil moisture content is disclosed. At step 302, the system 100 utilizes a multiplexer 102 to route one or more frequency signals generated by four resistive sensors 106. The multiplexer 102 sequentially selects each sensor's signal and directs it to the datalogger 104 for processing. At step 304, the system 100 can also connect the multiplexer 102 to a datalogger 104 specifically configured for soil moisture monitoring. The datalogger 104 is designed to receive the frequency signals transmitted by the multiplexer 102, facilitating data acquisition from the resistive sensors. At step 306, the datalogger 104 employs proprietary equations configured within to convert resistance values measured by the four resistive sensors into equivalent frequency signals. The equations are tailored to accurately translate resistance values into frequency signals, ensuring precise soil moisture measurements.
[0072] Further, at step 308, the datalogger 104 receives the frequency signals from the resistive sensors and applying the plurality of proprietary equations derived by the datalogger 104 to convert them into one or more centibar values. The conversion process provides meaningful soil moisture data in centibars, representing soil water tension levels. Finally, at step 310, the method 300 includes supplying an Alternating Current (AC) excitation to the connected four resistive sensors through the 555 timer IC 112, which supplies the pseudo-AC excitation signal on its "OUT" pin that goes to the sensors 106. As soon as the 555 timer is powered on, the signal is generated and when the multiplexer is enabled, this goes to the sensor. This pseudo-AC excitation signal safeguards the resistive sensors 106 against degradation caused by electrode corrosion, ensuring their long-term reliability and accuracy in soil moisture measurement.
[0073] In an embodiment, the method 300 includes dynamically adjusting the sampling rate of the resistive sensors based on environmental conditions or system 100 requirements. The datalogger 104 monitors factors such as soil moisture variability, weather patterns, or crop-specific needs and adapts the frequency of data acquisition accordingly. For example, during periods of significant soil moisture changes or high crop water demand, the sampling rate may increase to capture more frequent measurements for accurate monitoring and irrigation management. Conversely, during stable soil moisture conditions, the sampling rate may decrease to conserve power and optimize data storage efficiency.
[0074] In another embodiment, a specific data transmission protocol can be implemented between the multiplexer 102, datalogger 104, and external monitoring devices. The method 300 defines standardized communication protocols, including data formatting, packet structure, and error-checking mechanisms, to ensure reliable transmission of soil moisture data. For instance, the method 300 may specify protocols such as Universal Asynchronous Receiver-Transmitter (UART), Serial Peripheral Interface (SPI), or Inter-Integrated Circuit (I2C) for seamless data exchange between system 100 components. The standardized protocols can enhance interoperability and compatibility with various monitoring systems, enabling seamless integration into existing agricultural or environmental monitoring networks.
[0075] In an embodiment, the method 300 incorporates error handling mechanisms and calibration procedures to ensure measurement accuracy and reliability. The datalogger 104 includes algorithms for detecting and correcting measurement errors, such as sensor drift, noise, or signal interference. Additionally, the method 300 includes calibration routines to calibrate the resistive sensors and compensate for environmental factors, sensor aging, or manufacturing variations. Calibration procedures may involve applying known reference values or conducting field calibration tests to validate sensor accuracy and consistency. Error handling and calibration mechanisms enhance the precision and trustworthiness of soil moisture measurements, providing users with confidence in the monitoring system’s 100 performance.
[0076] In another embodiment, the system 100 enables remote configuration and control of the soil moisture monitoring system 100 using external devices or network interfaces. The method 300 includes implementing remote access protocols, such as HTTP (Hypertext Transfer Protocol) or MQTT (Message Queuing Telemetry Transport), to establish communication between the datalogger 104 and external control interfaces, such as web browsers, mobile applications, or cloud-based platforms. Users can remotely configure system 100 parameters, set measurement intervals, adjust threshold values, and receive real-time alerts or notifications based on soil moisture data. Remote configuration and control capabilities enhance system 100 flexibility and accessibility, allowing users to monitor and manage soil moisture conditions from anywhere with internet connectivity.
[0077] In an embodiment, the method 300 includes data analysis and reporting functionalities to derive insights from soil moisture measurements and generate actionable recommendations. The datalogger 104 integrates analytical algorithms for processing and interpreting soil moisture data, such as trend analysis, anomaly detection, or predictive modeling. Users can access analytical reports, graphical visualizations, and summary statistics to assess soil moisture trends, identify patterns, and make informed decisions regarding irrigation scheduling, crop management, or soil conservation practices. Data analysis and reporting features empower users to optimize water resources, maximize crop yield, and mitigate environmental risks associated with soil moisture variability.
[0078] In an embodiment, in addition to providing AC excitation to the four resistive sensors, the system 100 further comprises the capability to adjust the excitation frequency. The adjustment can be aimed at optimizing sensor performance while simultaneously reducing power consumption in the resistive sensors. By fine-tuning the excitation frequency based on sensor characteristics and environmental conditions, the system 100 can enhance sensor sensitivity and accuracy, thereby improving overall performance. Furthermore, optimizing the excitation frequency helps minimize power consumption in the resistive sensors, contributing to energy efficiency and prolonging battery life in battery-operated systems. This dual functionality of frequency adjustment not only ensures precise soil moisture measurements but also enhances the sustainability and longevity of the monitoring system 100, making it well-suited for long-term deployment in agricultural, environmental, and landscaping applications.
[0079] In another embodiment, the method 300 further encompasses the storage of one or more calibration coefficients specific to each of the four resistive sensors within the datalogger 104. The coefficients are vital for ensuring the accurate conversion of resistance values to frequency signals. By storing calibration coefficients tailored to the individual characteristics and response curves of each sensor, the datalogger 104 can precisely translate resistance measurements into frequency signals, thereby enhancing the accuracy and reliability of soil moisture data. The customized calibration approach accounts for variations in sensor performance, environmental conditions, and manufacturing tolerances, ensuring consistency and fidelity in soil moisture measurements across different sensors. By incorporating sensor-specific calibration coefficients into the datalogger’s 104 memory, the method 300 enables seamless and reliable data acquisition, facilitating informed decision-making in agricultural, environmental, and landscaping applications.
[0080] FIG. 4 illustrates the overall IoT infrastructure of the system, in accordance with an embodiment of the present disclosure.
[0081] Referring to FIG. 4, the IoT connectivity sub system 114 is disclosed, wherein the data from the device 100 is transferred to a cloud server 402, wherein the data is accessible by a farmer 406 through a mobile application 404 connected to the cloud server 402. The farmer 406 can access data related to the sensors 106 through the mobile application 404 and understand more about the soil moisture absorption properties of the sensors 106, and whether they need any upgradation, replacement, or repair.
[0082] It is to be appreciated by a person skilled in the art that while various embodiments
of the present disclosure have been elaborated for a system and method for measuring a soil moisture content and a method thereof. However, teachings of the present disclosure are also applicable for other types of applications as well, and all such embodiments are well within the scope of the present disclosure. However, a system and method for measuring a soil moisture content and a method thereof, and all such embodiments are well within the scope of the present disclosure without any limitation.
[0083] Moreover, in interpreting the specification, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refer to at least one of something selected from the group consisting of A, B, C….and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.
[0084] While the foregoing describes various embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof. The scope of the disclosure is determined by the claims that follow. The disclosure is not limited to the described embodiments, versions or examples, which are comprised to enable a person having ordinary skill in the art to make and use the disclosure when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE PRESENT DISCLOSURE
[0085] The proposed disclosure provides a system that provides accurate and precise soil water potential measurements, that represent the efforts required by the crop root to absorb water, thereby enabling informed data driven decision making in agricultural irrigation, environmental monitoring, and landscaping.
[0086] The proposed disclosure provides a system that offers versatility in monitoring soil moisture levels across different agricultural fields or environmental settings.
[0087] The proposed disclosure provides a system that monitors soil moisture data and adjust system settings remotely, providing convenience and flexibility in managing irrigation schedules and optimizing water usage.
[0088] The proposed disclosure provides a system that optimizes excitation frequency and reduce power consumption in resistive sensors contributes to energy efficiency, extending battery life and reducing overall operational costs.
, Claims:1. A system (100) for soil moisture monitoring, the system (100) comprising:
a CMOS 555 timer (112) with Fmax of 1.8MHz to 3MHz working in an astable multivibrator mode that produces a frequency signal proportional to the sensor resistance;
a multiplexer (102) for connecting up to four resistive sensors to the 555 timer IC (106) forming the instrumentation circuit;
a datalogger (104) for soil moisture monitoring, wherein the datalogger (104) has a microcontroller that controls the multiplexer channel selection, reads the frequency signal from the instrumentation circuit and calculates soil water potential in CB values using a plurality of proprietary equations (102);
a timer capture and conversion module (108) intrinsic to the microcontroller to receive the frequency signals and convert them to one or more centibar values using the plurality of proprietary equations derived by the datalogger (104); and
a IoT connectivity module (114) to transmit the soil water potential sensor data to other systems over LoRa or to a cloud platform using 4G or 5G cellular modem.
2. The system (100) as claimed in claim 1, wherein the datalogger (104) is further configured to store one or more calibration coefficients specific to each of the four resistive sensors (106) for an accurate conversion of the one or more resistance values to the equivalent frequency signals.
3. The system (100) as claimed in claim 1, wherein the timer capture and conversion module (108) is configured to receive the frequency signals for conversion to centibar values employs one or more temperature compensation algorithms to account for any variations in a performance of the four resistive sensors (106) due to temperature changes.
4. The system (100) as claimed in claim 1, wherein the datalogger (104) is equipped with one or more data logging capabilities to store a historical soil moisture data for analysis.
5. The system (100) as claimed in claim 1, wherein the datalogger (104) is equipped with one or more self-diagnostic capabilities to detect any sensor (106) malfunctions in data acquisition, facilitating maintenance and troubleshooting.
6. The system (100) as claimed in claim 1, wherein the system (100) further comprises a communication interface integrated with the datalogger (104), to facilitate real-time monitoring of the centibar values obtained.
7. A method (300) for soil moisture monitoring, the method (300) comprising:
The 555 timer IC (112) that produces pseudo-AC power signal to the sensors (106) connected via the multiplexer along with DC blocking capacitors to ensure no DC power enters the sensor thereby extending the sensor life;
routing signals from four resistive sensors (106) using a multiplexer (102) to a 555-instrumentation circuit which produces equivalent frequency signal based on the sensor resistance;
connecting the 555-instrumentation circuit to a datalogger (104) configured for soil moisture monitoring, wherein the datalogger (104) receives the frequency signals from the instrumentation circuit; and
converting the frequency signal (106) to equivalent CB values using a plurality of proprietary equations configured within the datalogger (104).
8. The method (300) as claimed in claim 7, wherein providing the AC excitation to the four resistive sensors (106) further comprising adjusting an excitation frequency to optimize a sensor (106) performance and reduce power consumption in the four resistive sensors (106).
9. The method (300) as claimed in claim 8, wherein the method (300) further comprising storing one or more calibration coefficients specific to each of the four resistive sensors (106) within the datalogger (104) for accurate conversion of resistance values to frequency signals.