Transpiration measurement sensor, transpiration measurement device, and transpiration measurement method

Abstract

According to one aspect, the present invention provides a transpiration measurement device with which it is possible to easily measure transpiration speed and transpiration amount from a state in which substantially no transpiration occurs to a state in which a large amount of moisture is released or a large amount of droplets are generated in a supersaturated environment in which relative humidity exceeds 100%. A transpiration measurement device according to an embodiment of the present invention comprises a sensor having a structure in which first thin wire electrodes composed of a material containing a first metal and / or carbon and second thin wire electrodes composed of a material containing a second metal different from the first metal are alternately arranged in at least a partial region on a substrate in which at least the surface thereof has insulating properties. The transpiration measurement device is configured to measure a current flowing between the first and second thin wire electrodes.

Description

Transpiration measurement sensor, transpiration measurement device, and transpiration measurement method

[0001] The present invention relates to an transpiration measuring sensor, an transpiration measuring device, and an transpiration measuring method.

[0002] Plant growth is highly dependent on the rate and amount of water vapor (also referred to as moisture) released from leaves, i.e., the transpiration rate and amount. Therefore, accurately measuring the transpiration rate and amount from plants is extremely important for the advancement of agriculture, including thorough crop growth management and quality control. For example, accurately measuring the transpiration rate from plants in a greenhouse and using the measured values ​​to monitor transpiration rate would enable the control of irrigation amounts and humidity conditions in greenhouse cultivation. Furthermore, in order to increase the sugar content of fruits and vegetables, there is a cultivation method in which water is provided at a low level during the growth stage without causing the crop to wither, thereby causing water stress. In this case, accurate measurement of transpiration rate would also enable the achievement of both high sugar content and a secure harvest.

[0003] As disclosed in Patent Document 1, methods for determining transpiration rate using humidity sensors have been investigated, and devices for evaluating transpiration rate from a single leaf or a single plant surrounded by a cover are commercially available. However, no methods or devices for evaluating macro-level transpiration rate for an entire greenhouse have been found. A method using the saturation deficit (the difference between the saturated absolute humidity and the measured value) within a greenhouse as a criterion for transpiration rate has also been proposed, but this method has the problem of being unable to estimate transpiration rate in high-humidity environments with relative humidity of 100% or higher, i.e., conditions exceeding the condensation threshold. Furthermore, this method is only capable of grasping transpiration trends and is not easily applicable to precise growth management. Therefore, there has been a strong demand for a method and device that can easily measure transpiration rate and transpiration rate over a wide range, from conditions where almost no transpiration occurs to conditions where a large amount of droplets are generated in a supersaturated environment with a relative humidity of over 100%.

[0004] JP 2014-215215 A International Publication No. 2016 / 013544

[0005] The problem that the present invention aims to solve is to provide a sensor and device that can easily measure the transpiration rate and amount from a state where almost no transpiration occurs to a state where the relative humidity reaches 100% and further exceeds 100% to become supersaturated, causing a large amount of droplets to form or a large amount of water to be released, as well as a measurement method using these.

[0006] The present invention has the following configurations: (Configuration 1) An evaporative measurement sensor having a structure in which first thin-wire electrodes made of a material containing at least one of a first metal and carbon and second thin-wire electrodes made of a material containing a second metal different from the first metal are alternately arranged in at least a partial area on an insulating substrate, at least the surface of which is insulating. (Configuration 2) An evaporative measurement device for measuring evaporative activity from an object to be measured, comprising: a sensor having a structure in which first thin-wire electrodes made of a material containing at least one of a first metal and carbon and second thin-wire electrodes made of a material containing a second metal different from the first metal are alternately arranged in at least a partial area on an insulating substrate, at least the surface of which is insulating, and a signal processing device that measures the current flowing between the first thin-wire electrodes and the second thin-wire electrodes. (Configuration 3) The evaporative measurement device according to Configuration 2, wherein the evaporative activity is an evaporative rate. (Configuration 4) The transpiration measuring device of Configuration 2 or 3, wherein the distance between the first thin wire electrode and the second thin wire electrode is constant in the region. (Configuration 5) The transpiration measuring device of Configuration 4, wherein the distance is 100 nm or more and 10 μm or less. (Configuration 6) The transpiration measuring device of any of Configurations 2 to 5, wherein the first metal is selected from the group consisting of gold, platinum, silver, titanium, and alloys thereof. (Configuration 7) The transpiration measuring device of any of Configurations 2 to 6, wherein the material containing the second metal is selected from the group consisting of silver, copper, iron, zinc, nickel, cobalt, aluminum, tin, chromium, molybdenum, manganese, magnesium, and alloys thereof. (Configuration 8) The transpiration measuring device of any one of Configurations 2 to 7, wherein at least one of the first thin wire electrode and the second thin wire electrode is provided in a plurality of lines, and the first thin wire electrode and the second thin wire electrode extend from opposite directions toward each other, thereby running parallel to each other. (Configuration 9) The transpiration measuring device of any one of Configurations 2 to 8, wherein the object to be measured is a plant. (Configuration 10) A transpiration measuring method for measuring at least one of the amount of transpiration and the transpiration rate from an object to be measured, using the transpiration measuring device of any one of Configurations 2 to 8.(Configuration 11) A step of preparing a humidity sensor and a galvanic current detection type droplet sensor; a step of placing the humidity sensor in an experimental environment with a relative humidity of 100% or less, acquiring output data from the humidity sensor under multiple conditions of different humidity and temperature, and measuring changes in relative humidity in the experimental environment; a step of calculating absolute humidity from the relative humidity and the temperature; a step of acquiring teacher data consisting of data on the rate of change in the amount of water vapor in the experimental environment based on the data on changes in absolute humidity; a step of placing the droplet sensor in a measurement environment and acquiring output data from the droplet sensor in the measurement environment; a step of comparing the teacher data with the output data of the droplet sensor to determine correlation; a step of calculating a conversion coefficient α that converts the output value P of the droplet sensor to the rate of change S of the amount of water vapor in the measurement environment from the slope of the output data of the droplet sensor that is found to be correlated with the teacher data and the output data of the droplet sensor; and a step of placing the droplet sensor in the measurement environment of the object to be measured and obtaining the output P of the droplet sensor. ｍｅａｓｕｒｅ and a step of obtaining S ｍｅａｓｕｒｅ = α × P ｍｅａｓｕｒｅ From the evaporation rate S of the object to be measured ｍｅａｓｕｒｅ (Configuration 12) The transpiration measurement method according to configuration 11, wherein the method for determining the correlation is one selected from the group consisting of regression analysis, t-test, and z-test. (Configuration 13) According to the transpiration measurement method according to configuration 11 or 12, the transpiration rate S is determined using the droplet sensor in the measurement environment of the object to be measured. ｍｅａｓｕｒｅ a step of continuously measuring the transpiration rate S for a predetermined time t or more; ｍｅａｓｕｒｅover the predetermined time t to calculate an amount of evaporation V at the predetermined time t. (Configuration 14) The method for measuring evaporation from the object to be measured according to any one of Configurations 11 to 13, wherein the droplet sensor has a structure in which first thin-wire electrodes made of a material containing at least one of a first metal and carbon and second thin-wire electrodes made of a material containing a second metal different from the first metal are alternately arranged in at least a partial area on an insulating substrate, at least the surface of which is insulating. (Configuration 15) The method for measuring evaporation according to any one of Configurations 11 to 14, wherein a space consisting of a colony area in which a plurality of evaporating bodies that emit water vapor are present in colonies and a blank area in which no evaporating bodies are present forms an enclosed space isolated from outside air, and at least one droplet sensor is installed in the colony area and at least one droplet sensor is installed in the blank area, and measurement is performed using the method for measuring evaporation according to any one of Configurations 11 to 14.

[0007] The present invention provides a sensor and device that can easily measure the transpiration rate and amount from a state where almost no transpiration occurs to a state where the relative humidity reaches 100% and further exceeds 100% to become supersaturated, causing a large amount of droplets to form or a large amount of water to be released, as well as a transpiration measurement method using these.

[0008] Furthermore, the transpiration measurement method of the present invention has the advantage that it is possible to measure the amount of transpiration from a local situation such as within a plant community (for example, a crop in a greenhouse) to a macro situation such as the entire greenhouse. The unit of the amount of transpiration measured by the present invention is [g / m ３ ], and as this unit indicates, the local transpiration rate [g] within a specific canopy, etc., is proportional to the volume [m ３ On the other hand, the macroscopic evaporation rate [g] for the entire greenhouse can be calculated by multiplying the evaporation rate [g / m] obtained from one sensor. ３ ] to the volume of the entire house [m ３ ], or by dividing the greenhouse into several virtual sections and multiplying the transpiration rate [g / m ３ ] and the volume of each compartment [m ３] and sum up the values ​​obtained for all sections.

[0009] 5A-5D are diagrams showing an outline of the configuration of the transpiration measurement device of the present invention, where (a) is a plan view and (b) is an A-A' cross-sectional view of the droplet sensor unit.

[0024] FIG. 5B is a diagram explaining the operating principle of the droplet sensor unit of the transpiration measurement device of the present invention.

[0025] FIG. 5C is a flowchart showing the transpiration measurement method of the present invention.

[0026] (a)-(d) are diagrams explaining the transpiration measurement method of the present invention.

[0027] FIG. 5C is a measurement example according to the embodiment, showing the change in bubbler temperature [°C] over time.

[0028] FIG. 5D is a measurement example according to the embodiment, showing the environmental temperature [°C] and the relative humidity [%RH] on the sensor surface.

[0029] FIG. 5E is a measurement example according to the embodiment, showing the measurement results of current values ​​[pA] obtained by two types of droplet sensors with different thin-wire electrode spacings, processed as digital signals, and the resistance values ​​[Ω] of the thin-wire electrodes.

[0029] FIG. 5F is a measurement example according to the embodiment, showing analog signal data (raw data) before the measurement results of current values ​​shown in FIG. 5C are obtained.

[0029] (a) and (b) are measurement examples according to the embodiment, showing photographs showing transpiration measurement in a greenhouse.

[0010] <Device Configuration> As shown in FIG. 1( a ), the transpiration measuring device 101 of the present invention is a device equipped with a droplet sensor unit 10 and a sensor signal processing and analysis unit 14 .

[0011] A first feature of the transpiration measuring device 101 of the present invention is the use of a galvanic current detection type droplet sensor 10 (described below) as a sensor for measuring transpiration. The droplet sensor 10 senses and detects droplets formed between a first thin-wire electrode and a second thin-wire electrode by sensing the current flowing between the first thin-wire electrode and the second thin-wire electrode. The present inventor discovered a correlation between the size and number of droplets detected by the droplet sensor 10 and the amount of transpiration, leading to the invention. The droplet sensor 10 tends to increase in frequency of sensor response as the amount of transpiration increases. In addition, the droplet sensor 10 can detect increases in size and number of droplets even in a supersaturated state where the relative humidity exceeds 100%, making it suitable for use as a sensor (a sensor for measuring transpiration) constituting the droplet sensor unit 10 of the transpiration measuring device 101 of the present invention. Therefore, as shown in the examples, the transpiration measuring device 101 equipped with the droplet sensor 10 is capable of measuring the transpiration rate and amount even in a supersaturated state where the relative humidity exceeds 100%, and meets the performance requirements for plant growth and quality control and for the advancement of agriculture.

[0012] The second feature of the transpiration measuring device 101 of the present invention is that, in linking the output value (output current value) of the droplet sensor 10 to the amount of transpiration (transpiration rate), a conversion coefficient is calculated by comparing the output value (output current value) of the droplet sensor 10 with the amount of water vapor in the experimental environment, which is calculated from the absolute humidity calculated from the relative humidity and environmental temperature, in an experimental environment with a relative humidity of 100% or less. In other words, considering the operating principle of a galvanic current detection type droplet sensor (see Figure 2 below), one might assume that even if the droplets (water droplets) formed between the thin wire electrodes are water vapor due to plant transpiration (i.e., even if the droplets form between the thin wire electrodes due to water vapor resulting from plant transpiration), it is possible to estimate the amount of transpiration or the transpiration rate in a similar manner to monitoring the wet / dry state of the environment. However, the inventors have found that this assumption is only applicable in simulated and limited environments, and that in environments where plants actually grow (real environments), it is difficult to unambiguously evaluate the amount of transpiration or the transpiration rate from the droplet sensor response (droplet detection / measurement signal). As described above, the inventors have devised a method for calculating the amount of transpiration or the transpiration rate of a target plant from the micro (local) sensor response in a real environment by evaluating the correlation between the amount of water vapor in the environment obtained in a specified experimental environment and the macro (average) sensor response and calculating a conversion coefficient, thereby completing the present invention. In the case of supersaturated conditions where the relative humidity exceeds 100%, as described above, the droplet sensor 10 is able to detect an increase in the size and number of droplets even under such supersaturated conditions, and extrapolation is performed by estimating a value nominally exceeding 100% (including condensation). This ensures accuracy and precision in measuring evaporation over a wide range.

[0013] As shown in FIG. 1( a), the transpiration measurement device 101 may be an integrated measurement device having the droplet sensor unit 10 and the sensor signal processing and analysis unit 14, with the droplet sensor unit 10 and the sensor signal processing and analysis unit 14 electrically connected by a signal line 16, or a separate measurement device separated into a sensor device having the droplet sensor unit 10 and a signal processing unit having the signal processing and analysis unit 14. In the case of the separate type, wireless communication is intended as a means for transmitting the output signal from the droplet sensor unit 10 to the signal processing and analysis unit 14, but media such as an SSD (Solid State Drive) or a memory card may be used instead of wireless communication. Here, the integrated type has the advantage of making the device easier to handle, while the separate type has the advantage that when multiple sensors are used, the signal processing unit and analysis unit can be shared, which is efficient and makes it possible to reduce the price of the entire device.

[0014] The droplet sensor unit (droplet sensor) 10 is a galvanic current detection type droplet sensor. The galvanic current detection type droplet sensor is mounted on a substrate 11 as shown in FIG. ｓｕｂ A first thin wire electrode 12 made of metal A and a second thin wire electrode 13 made of metal B are arranged side by side on the surface 11 of the substrate 11, and when a conductive liquid droplet such as a water droplet touches the first thin wire electrode 12 and the second thin wire electrode 13, the sensor detects the galvanic current flowing between the two thin wire electrodes, thereby detecting the presence or generation of the liquid droplet. Such a galvanic current detection type liquid droplet sensor is disclosed, for example, in Patent Document 2. Here, the substrate 11 ｓｕｂ At least the surface 11 of the substrate 11 is made of an insulating material. ｓｕｂ Examples of suitable substrates include silicon oxide film substrates on silicon, substrates made of synthetic quartz or glass, plastic substrates made of polycarbonate or the like, and metal insulating substrates in which an oxide film or organic insulating film is formed on a metal plate such as aluminum. Metals A and B constituting first fine wire electrode 12 and second fine wire electrode 13 are different metals, and may be either simple metals or alloys. Either metal A or metal B may be carbon, a metal carbide, or a carbide alloy.

[0015] Here, it is preferable that the distance d (see FIG. 1(b)) between the first thin-wire electrode 12 and the second thin-wire electrode 13 is constant. A constant distance d improves the stability and sensitivity of droplet detection, thereby improving the stability and sensitivity of evaporation measurement by the evaporation measurement device 101. Furthermore, the distance d is preferably 100 nm or more and 10 μm or less, and more preferably 500 nm or more and 10 μm or less. When the distance d is within this range, it is easy to ensure the stability of droplet detection, making it possible to more stably measure evaporation by the evaporation measurement device 101.

[0016] The first thin wire electrode 12 and the second thin wire electrode 13 are made of a material selected from the group consisting of metal, alloy, metal carbide, alloy carbide, and carbon, and are selected so as to have different electrochemical potentials. For example, the first metal-containing material constituting the first thin wire electrode 12 may be a material selected from the group consisting of gold (Au), platinum (Pt), silver (Ag), titanium (Ti), and alloys thereof. Alternatively, carbon (C), metal carbide, or alloy carbide may be used as the first metal. The second thin wire electrode 13 is made of a material selected from the group consisting of silver (Ag), copper (Cu), iron (Fe), zinc (Zn), nickel (Ni), cobalt (Co), aluminum (Al), tin (Sn), chromium (Cr), molybdenum (Mo), manganese (Mn), magnesium (Mg), and alloys thereof.

[0017] 1(a), at least one of the first thin wire electrodes 12 and the second thin wire electrodes 13 is preferably provided in a plurality of wires, and the first thin wire electrodes 12 and the second thin wire electrodes 13 extend from opposite directions toward each other, so that they run parallel to each other. This increases the packing density (element density) of the sensor device, and improves the sensitivity, reliability, and stability of droplet detection.

[0018] As shown in FIG. 1A , the electrodes (current collectors) of the droplet sensor unit 10 are composed of a first electrode 32 electrically connected to the first thin-wire electrode 12 and a second electrode 33 electrically connected to the second thin-wire electrode 13. As mentioned above, the metal (material) constituting the first thin-wire electrode 12 is different from the metal (material) constituting the second thin-wire electrode 13. From the perspective of wiring fabrication, it is preferable that the first thin-wire electrode 12 and the first electrode 32, and the second thin-wire electrode 13 and the second electrode 33, are each composed of the same material. On the other hand, from the standpoint of convenience of the wiring drawn out from the droplet sensor unit 10, it is preferable that the first electrode 32 and the second electrode 33 are composed of the same material. From the latter standpoint, it is preferable to use aluminum, for example, as the first electrode 32 and the second electrode 33, because it has low electrical resistance and can be relatively inexpensive.

[0019] In the case of the integrated measuring device described above, the droplet sensor unit 10 is electrically connected to the sensor signal processing and analysis unit 14 via a signal line 16 (see FIG. 1(a)). As shown in FIG. 1(a), the sensor signal processing and analysis unit 14 has at least two functional units, a current value measurement unit 41 and a current value determination and analysis unit 42, and the current value measurement unit 41 and the current value determination and analysis unit 42 are electrically connected by a signal line 43.

[0020] The current value measuring unit 41 measures the value of the galvanic current flowing between the first thin-wire electrode 12 and the second thin-wire electrode 13. The measurement method may be either a direct current measurement using an ammeter or a measurement method in which the galvanic current is amplified using an amplifier. The former method of directly measuring the current is simple and can be manufactured at low cost, while the latter method of using an amplifier is suitable for improving measurement accuracy. Representative amplifier methods include a charge amplifier method and an analog amplifier method. The analog amplifier method inverts the phase of a signal from one channel and then calculates the difference with the signal from the other channel. This method is particularly preferred because it can increase the S / N ratio by 10 times or more while keeping costs low.

[0021] The current value determination and analysis unit 42 has the following functions: a function to input the droplet detection and measurement signal, which is an output signal from the droplet sensor unit 10, the relative humidity measurement signal from the humidity sensor, and the environmental temperature measurement signal at the installation location of the droplet sensor 10; a function to calculate the absolute humidity from the relative humidity measurement signal and the environmental temperature measurement signal; and a function to calculate the time change Δ of the absolute humidity. Ｈ The function to calculate the absolute humidity change over time Δ Ｈ corresponds to the rate of change of the amount of water vapor in the environment; and the time change Δ of the output signal of the droplet sensor 10. Ｗ A function to calculate the time change Δ of the output signal of the droplet sensor 10 Ｗ The time change Δ of the absolute humidity Ｈ From the above, the time change Δ of the output signal of the droplet sensor 10 Ｗ The rate of change of the amount of water vapor in the environment Δ Ｈ a function for calculating a conversion coefficient α for converting the environmental conditions and the conversion coefficient α into a list, and storing and saving the list; a function for storing and saving the output signal P of the droplet sensor 10 from the following equation (1): ｍｅａｓｕｒｅ Using the conversion coefficient α, the transpiration rate S ｍｅａｓｕｒｅ The function to be sought. ｍｅａｓｕｒｅ = α × P ｍｅａｓｕｒｅ ...(1)

[0022] For this reason, as shown schematically in FIG. 1( a), the current value determination and analysis unit 42 includes an input unit for a signal line 43 from the current value measurement unit 41, an input unit for a signal line 44 from a humidity sensor (not shown), an input unit for a signal line 45 from an optional temperature sensor (not shown), and an output unit for an output line 46. In FIG. 1( a), the arrows pointing toward the current value determination and analysis unit 42 represent the input units, and the arrows pointing away from the current value determination and analysis unit 42 represent the output units. Note that instead of inputting temperature data from the temperature sensor to the current value determination and analysis unit 42 as an electrical signal via the signal line 45, a system in which a numerical value of the temperature is input may be used. Furthermore, the means for transmitting each signal may be wireless instead of via a signal line, and the form of each signal may be either analog or digital.

[0023] Specifically, the current value determination and analysis unit 42 is composed of a computing function device such as a CPU (Central Processing Unit), an MPU (Micro Processing Unit), or a microcomputer, a memory such as a DRAM, an SRAM, or a flash memory, and a storage such as an SSD, a flash memory, or an HDD. For example, a PC can be used as the current value determination and analysis unit 42.

[0024] The transpiration rate is directly measured by the transpiration measuring device 101 of the present invention. The amount of transpiration can be calculated by performing time integration on the transpiration rate measurement value ΔV(t) at each measurement time t.

[0025] <Measurement Method> The transpiration measurement method of the present invention will be described with reference to FIGS. 3 and 4. FIG.

[0026] First, a humidity sensor and a galvanic current detection type droplet sensor 10 are prepared (step S11). Here, the humidity sensor is a sensor that measures at least relative humidity and is not particularly limited. Generally, commercially available relative humidity sensors can be used without any problems. For example, for greenhouses, ThinkingFarm (manufactured by Agroinfo LLC), Agrilog (manufactured by IT Kobo Z Co., Ltd.), and Profarm (Denso Corporation) are available. For general-purpose products, the Ondotori series (manufactured by T&D Corporation) and HygroFlex series (manufactured by Rotronic Co., Ltd.) are available. For element-level products, the SHT3x series (manufactured by Sensirion Co., Ltd.) can be mentioned. It is preferable that the humidity sensor also has the function of measuring temperature. Alternatively, a temperature sensor may be prepared separately from the humidity sensor.

[0027] Next, the humidity sensor is placed in an experimental environment with a relative humidity of 100% or less, and output data from the humidity sensor is acquired under multiple conditions of different humidity and temperature to measure the change in relative humidity in the experimental environment (step S12, FIG. 4(a)). The experimental environment is not particularly limited as long as it is an environment with a relative humidity of 100% or less and allows output data from the humidity sensor to be acquired under multiple conditions of different humidity and temperature. Examples include a room (in a laboratory) or a space (in an experimental box) with a certain volume. Alternatively, if the measurement environment described below is a greenhouse (e.g., an agricultural greenhouse), the experimental environment may be the greenhouse or a space simulating the environment within the greenhouse. Here, FIG. 4(a) schematically illustrates how the environmental temperature (air temperature) [°C] and relative humidity [% RH] change with time t. The measurement time interval can be set to any value.

[0028] Thereafter, absolute humidity is calculated from the relative humidity and the temperature (step S13). Here, the absolute humidity may be calculated by a general conversion method, such as determining the saturated water vapor pressure, multiplying it by the relative humidity to determine the actual water vapor partial pressure, and then applying this value to a physical formula. In this specification, absolute humidity is defined as volumetric (volume) absolute humidity [g / m] unless otherwise specified. ３ ], typically calculated using the following formula: absolute humidity [g / m ３ ] = 217 × water vapor partial pressure [hPa] / (273.15 + temperature [°C]) The saturated water vapor pressure and water vapor partial pressure can be calculated using, for example, the following formula: Saturated water vapor pressure [hPa] = 6.11 × 10^ (7.5 × temperature [°C] / (237.3 + temperature [°C])) Water vapor partial pressure [hPa] = saturated water vapor pressure [hPa] × relative humidity [%] / 100

[0029] Thereafter, based on the change data of the absolute humidity, teacher data consisting of change rate data of the amount of water vapor in the experimental environment is obtained (step S14, FIG. 4(b)). Here, FIG. 4(b) shows the absolute humidity [g / m ３ ] changes with time t, and the amount of change in absolute humidity per unit time [g / m ３ / min] is the rate of change of the amount of water vapor in the experimental environment.

[0030] Next, the droplet sensor 10 is placed in a measurement environment, and output data from the droplet sensor 10 in the measurement environment is acquired (step S15, FIG. 4(c)). The measurement environment is intended to be an environment in which an object (measurement object) whose transpiration is to be measured exists or is intended to exist, and is typically an environment in which a target plant is grown or is intended to be grown. In one exemplary embodiment, the measurement environment is a greenhouse, more specifically, an agricultural greenhouse. Here, FIG. 4(c) schematically illustrates how the output value (sensor value [A]) of the droplet sensor 10 changes with time t, and shows that the change in the sensor value per unit time [A / min] can be obtained.

[0031] The training data is then compared with the output data of the droplet sensor 10 to determine the correlation (step S16). The correlation can be determined by one method selected from the group consisting of regression analysis, t-test, and z-test. Regression analysis can be extended to multivariate analysis, and the t-test is suitable for use when the population variance is unknown, while the z-test is suitable for use when the population variance is known.

[0032] Thereafter, a conversion coefficient α for converting the output value P of the droplet sensor 10 into the rate of change S of the amount of water vapor in the measurement environment is calculated from the slope of the output data of the droplet sensor 10 for which a correlation between the teacher data and the output data of the droplet sensor 10 has been confirmed (step S17, FIG. 4(d)). Here, FIG. 4(d) shows a graph in which the horizontal axis represents the amount of change in the sensor value per unit time shown in FIG. 4(c) (time change in the sensor value [A / min]) and the horizontal axis represents the amount of change in absolute humidity per unit time shown in FIG. 4(b) (rate of change in the amount of water vapor in the environment [g / m ３ The graph is shown with the vertical axis being the gradient [g / m ３ / A] is the above-mentioned conversion coefficient α. Note that the above-mentioned graph may be an approximated line (regression line).

[0033] Next, the droplet sensor 10 is placed in the measurement target environment of the object to be measured, and the output Pｍｅａｓｕｒｅ is calculated (step S18). Here, the measurement environment is intended to be the environment in which the object to be measured (i.e., the object whose transpiration is to be measured) is present, typically the environment in which the target plant is grown. In addition, in the present invention, the measurement environment may refer to a space smaller than the measurement environment. For example, in the above-exemplified embodiment, the measurement environment is inside a greenhouse (inside an agricultural greenhouse), whereas the measurement environment may be a portion of the object to be measured (e.g., a plant or crop leaf) or a certain space including that portion. In other words, in the present invention, the measurement environment is preferably a space including a portion of the object to be measured where transpiration is likely to occur. By placing the droplet sensor 10 in such a measurement environment, the transpiration amount or transpiration rate of the object to be measured (plant or crop) can be calculated from the sensor response obtained in a micro (local) space, such as around several leaves or a single leaf.

[0034] Finally, the above-mentioned formula (1) (S ｍｅａｓｕｒｅ = α × P ｍｅａｓｕｒｅ ) to calculate the evaporation rate S ｍｅａｓｕｒｅ For example, the output P of the droplet sensor 10 is calculated (step S19). ｍｅａｓｕｒｅ If z [A], the conversion coefficient α [g / m ３ / A] to obtain the evaporation rate S of the object to be measured. ｍｅａｓｕｒｅ is αz [g / m ３ ]

[0035] Furthermore, the evaporation measurement method of the present invention, as described above, is a method of measuring the evaporation rate S using the droplet sensor 10 in the measurement environment of the object to be measured. ｍｅａｓｕｒｅ The measurement of the transpiration rate S is continued for a predetermined time t or more. ｍｅａｓｕｒｅ is integrated over a predetermined time t to obtain the evaporation rate V [g / m ３ ] can be calculated.

[0036] In summary, the transpiration measurement method of the present invention uses a humidity sensor to acquire training data in an experimental environment of 100% or less relative humidity, analyzes whether there is a correlation between the training data and data acquired in the measurement environment using droplet sensor 10, determines a conversion coefficient α using the output data of droplet sensor 10 for which a correlation has been confirmed, and calculates the transpiration rate of the object being measured from the output of droplet sensor 10 in the measurement environment of the object being measured. Because the transpiration measurement method of the present invention includes a step of confirming the high correlation between the training data and the data acquired using droplet sensor 10, it has the advantage of being highly accurate, precise, and stable in measurement, and further capable of measuring the transpiration rate and amount even in supersaturated environments where the relative humidity exceeds 100%, making it a very effective method for plant growth and quality control and for improving the sophistication and efficiency of agriculture.

[0037] Furthermore, as shown in the examples, the transpiration measurement method of the present invention is a local measurement method capable of measuring transpiration based on the detection of minute droplets by the droplet sensor 10, and is characterized by high spatial resolution. This feature makes the transpiration measurement method of the present invention suitable for monitoring transpiration in situations, such as those often found in greenhouse cultivation, where a colony area where multiple transpiration bodies that emit water vapor grow is present and a blank area where no transpiration bodies are present, and the space formed by the colony area and the blank area forms an enclosed space isolated from the outside air. In other words, in such an environment, by installing at least one droplet sensor 10 in the colony area and at least one in the blank area, it is possible to understand the spatial distribution of transpiration within the greenhouse, such as by measuring changes in the transpiration rate and amount at any position in the colony area, as well as comparing the colony area and the blank area, thereby improving the management of greenhouse cultivation.

[0038] For example, assuming cultivation in a specific greenhouse, the conversion coefficient α obtained by performing the above steps S11 to S17 in that greenhouse as the measurement environment can be used in subsequent measurements in the same greenhouse. In other words, if the measurement environment of the object to be measured (a greenhouse in this example) is the same, it is assumed that steps S11 to S17 have already been performed in the previous measurement, and the output P of the droplet sensor 10 placed in that measurement environment can be used. ｍｅａｓｕｒｅ(step S18), and the evaporation rate S of the object to be measured is calculated using the above formula (1). ｍｅａｓｕｒｅ By calculating (step S19), the measurement of the transpiration rate of the object to be measured can be simplified. Of course, steps S11 to S17 may be performed each time a measurement is made to calculate the conversion coefficient α, and in this case, it is expected that more precise cultivation management will be possible. Furthermore, assuming cultivation in multiple greenhouses set up in a specific farmland (which may be interpreted more broadly as a district or area), for example, it may be possible to set a reference value for the conversion coefficient according to the volume of the farmland (district or area) and / or greenhouse by statistically analyzing the conversion coefficient α obtained by performing steps S11 to S17 on each greenhouse as the measurement environment. In such a case, it is assumed that steps S11 to S17 have already been performed in the first measurement in a certain greenhouse, and the output P of the droplet sensor 10 placed in that greenhouse (measurement target environment) can be calculated. ｍｅａｓｕｒｅ (Step S18), and the transpiration rate S of the object to be measured is calculated using the above-mentioned reference value as the value of α in the above formula (1). ｍｅａｓｕｒｅ (step S19), it may be possible to further simplify the measurement of the amount of evaporation of the object to be measured.

[0039] Example 1 In Example 1, a prototype of an evaporation measurement device 101 was produced using the droplet sensor 10 and a PC as the sensor and current value determination and analysis unit 42, and a demonstration experiment was conducted to demonstrate the concept of the evaporation rate measurement described above.

[0040] The prototype droplet sensor 10 is a substrate 11 whose surface is made of silica. ｓｕｂThis is a galvanic current detection sensor in which a first thin-wire electrode 12 and a second thin-wire electrode 13 are formed on the droplet sensor 10. The first thin-wire electrode 12 is made of gold (Au), has a line width of 2 μm, a thickness of 150 nm, and has 165 wires. The second thin-wire electrode 13 is made of aluminum (Al), has a line width of 2 μm, a thickness of 150 nm, and has 165 wires. The spacing d between the first thin-wire electrode 12 and the second thin-wire electrode 13 is constant, and multiple electrodes with a spacing of 500 nm (0.5 μm) and 10 μm were fabricated. A current measuring device (current value measuring unit 41) is connected to the droplet sensor 10 via cable or wirelessly, and the output of the current measuring device is sent to a PC via signal line 43 or wirelessly. Here, the current measuring device is homemade (custom-made), and a ThinkPad L570 (manufactured by Lenovo) is used as the PC.

[0041] The measurement procedure is as follows. First, a temperature and humidity sensor and the galvanic current detection type droplet sensor 10 were prepared (step S11 in Figure 3). Here, the temperature and humidity sensor used was an EE23 manufactured by E+E Elektronik. A cooling vapor saturation type bubbler me-40DPRT (manufactured by Micro Equipment Co., Ltd.) was placed in an experimental box (a closed space with a capacity of 50 mL), a thermocouple thermometer was installed in the saturation tank, and the temperature and humidity sensor and droplet sensor 10 were placed in the experimental box. The output signals from each sensor were configured to be sent to a PC via a wired connection if they were analog signals, or wirelessly if they were digital signals. The output signal from the droplet sensor 10 was configured to be sent from a current measuring device via the aforementioned analog amplifier type amplifier. Additionally, the surface temperature of the droplet sensor 10 (substrate 11 ｓｕｂThe temperature of the surface 11 of the saturation tank was monitored. Next, the bubbler was operated while monitoring the temperature of the saturation tank with a thermocouple thermometer, and the time change in relative humidity in the experimental box (experimental environment of 100% relative humidity or less) was measured with a temperature and humidity sensor (step S12). Then, absolute humidity was calculated from the relative humidity and temperature (step S13). Subsequently, based on the obtained absolute humidity change data, training data consisting of data on the rate of change in the amount of water vapor in the experimental environment was obtained (step S14). Here, the temperature in step S13 is the measurement result of the temperature (time change) in the experimental box using the temperature and humidity sensor. Next, using the same experimental environment as the measurement environment, output data from the droplet sensor 10 was obtained (step S15). The training data and the output data from the droplet sensor 10 were then compared to determine the correlation using a t-test (step S16). As a result, t > +2.0, which indicates a correlation of 95% or more, was obtained, confirming a high correlation.

[0042] Examples of measurement data are shown in Figures 5A to 5D. Here, Figure 5A shows the change in bubbler temperature (°C) over time, Figure 5B shows the environmental temperature (temperature inside the experimental box) (°C) and the relative humidity (%RH) on the sensor surface, Figure 5C shows the measurement results of current values ​​(pA) measured by two types of droplet sensors 10 with different thin-wire electrode spacings, processed as digital signals, and the resistance values ​​(Ω) of the thin-wire electrodes, and Figure 5D shows the analog signal data (raw data) before the current value measurement results shown in Figure 5C were obtained. These data were obtained by changing the bubbler conditions every 1200 seconds.

[0043] More specifically, the bubbler temperature is the temperature of the saturation tank that constitutes the bubbler. When the temperature of the saturation tank is determined, the water vapor partial pressure P ｂ [hPa] is determined and assumed to be equal to the saturated water vapor pressure [hPa]. ｂ When the air containing the saturated water vapor reaches a certain temperature T [℃], the saturated water vapor pressure P Ｔ Since the relative humidity [% RH] is theoretically determined by P ｂ [hPa] / P ＴIn this example, the water vapor partial pressure P ｂ The relative humidity [%RH] on the sensor surface was calculated based on the relative humidity and environmental temperature measured by the temperature and humidity sensor, and the water vapor partial pressure P Ｅ [hPa], and the surface temperature T Ｓ [℃] to the saturated water vapor pressure P Ｓ [hPa] was calculated, and P Ｅ [hPa] / P Ｓ It was calculated as [hPa] x 100.

[0044] As a result, as time passed, the relative humidity on the sensor surface and the output values ​​from the droplet sensor 10 increased due to the increase in water vapor supplied from the bubbler, but the relative humidity on the sensor surface nominally saturated at a value above 100% (FIG. 5B). Meanwhile, the output value from the droplet sensor 10 continued to increase even after the relative humidity on the sensor surface saturated above 100% (after approximately 13,000 s) (FIG. 5C). This demonstrates that the transpiration measurement device and transpiration measurement method using the droplet sensor 10 of the present invention are capable of measuring transpiration even in supersaturated conditions where the relative humidity exceeds 100%.

[0045] Since this example is a demonstration experiment, the measurement environment is the same as the experimental environment, but even if the measurement environment is, for example, a greenhouse, the conversion coefficient α can be calculated according to the above procedure. Then, the liquid drop sensor 10 is placed in the measurement target environment of the object to be measured (for example, inside a greenhouse where the target plant is growing), and the output P ｍｅａｓｕｒｅ (step S18), and the above formula (1) (S ｍｅａｓｕｒｅ = α × P ｍｅａｓｕｒｅ ) to calculate the evaporation rate S ｍｅａｓｕｒｅ(Step S19) Furthermore, by multiplying the volume of the local space around the droplet sensor 10, it is possible to determine the local transpiration rate, such as within a specific community where the droplet sensor 10 is installed, and the macroscopic transpiration rate, such as that of the entire greenhouse, can be determined by multiplying the transpiration rate obtained from one droplet sensor 10 by the volume of the entire greenhouse, or by virtually dividing the greenhouse into several compartments, multiplying the transpiration rate obtained from droplet sensors 10 installed in each compartment by the volume of each compartment, and then adding up the values ​​obtained for all the compartments.

[0046] Example 2 In Example 2, a total of 12 transpiration measurement devices (thin-wire electrode spacing d = 0.5 μm) prepared in Example 1 were installed in an agricultural greenhouse and measurements were performed. Measurements in the experimental environment were considered to be performed in steps S11 to S14 in Example 1. Measurements in the measurement environment were performed in the same manner as in Example 1, obtaining output data from the droplet sensor 10 in the greenhouse (step S15), comparing the above-mentioned training data with the output data from the droplet sensor 10, and determining the correlation by a t-test (step S16). A high correlation was confirmed. In addition, since a ThinkingFarm (manufactured by Agroinfo LLC) was also installed in the greenhouse as a temperature and humidity sensor, a high correlation was confirmed even when the greenhouse was treated as the experimental environment, training data was obtained by performing steps S11 to S14, and the training data was compared with the output data from the droplet sensor 10 to determine the correlation by a t-test. From the slope of the data from the droplet sensor 10 for which a correlation was thus confirmed, i.e., the relationship between the rate of change in absolute humidity, which represents the rate of change in the amount of water vapor in the experimental environment, and the amount of change in output of the droplet sensor 10 over time, a conversion coefficient α was calculated to convert the output value P of the droplet sensor 10 into the rate of change S of the amount of water vapor in the measurement environment (step S17). The conversion coefficient α was 0.55-0.68 for each sensor (average value for all sensors: 0.67).

[0047] The greenhouse measures approximately 50m x 40m x 3.5m and is used to cultivate cucumbers. The plants are cultivated in colonies consisting of 15 rows, with paths approximately 1m wide between the colonies.

[0048] In this example, as shown in Figure 6, multiple droplet sensors 10 were installed inside the canopy (Figure 6(a)) and outside the canopy (Figure 6(b)) to measure transpiration, and the differences in measurement values ​​were compared between the sensors installed inside the canopy (10 sensors in total), between the sensors installed outside the canopy (2 sensors in total), and between the sensors installed inside and outside the canopy. As a result, it was confirmed that a high correlation was obtained, with t > +2.0, where the correlation was 95% or higher, occurring in approximately 90% of the measurement period (number of days).

[0049] In this embodiment, the difference in the sensor response of the droplet sensor 10 inside and outside the canopy is considered to represent transpiration from the cultivated plants. ｍｅａｓｕｒｅ Based on this, the difference in sensor response between inside and outside the canopy was obtained, and this was applied to the above formula (1) to calculate the transpiration rate and amount of transpiration of the cultivated plant. As a result, it was confirmed that the transpiration measurement device and transpiration measurement method using the droplet sensor 10 of the present invention can measure transpiration from cultivated plants in an actual cultivation environment such as a greenhouse. Regarding the configuration of the transpiration measurement device used in this example, it was confirmed that the desired transpiration measurement was possible even when the current measurement device was changed from a homemade one to a commercially available one.

[0050] As described above, according to the present invention, it is possible to easily measure the transpiration rate and amount from plants over a wide dynamic range, from a state where almost no transpiration occurs to a state where a large amount of droplets are generated or a large amount of water is released in a supersaturated environment with a relative humidity of over 100%. Since the transpiration rate and amount are directly linked to plant growth and sugar accumulation, applying the method of the present invention to agriculture is expected to increase crop yields and improve the deliciousness of harvested products.

[0051] 10: droplet sensor unit, droplet sensor 11: substrate surface 11 ｓｕｂ: Substrate 12: First thin wire electrode (platinum) 13: Second thin wire electrode (aluminum) 14: Sensor signal processing and analysis unit 16: Signal line 32: First electrode (aluminum) 33: Second electrode (aluminum) 41: Current value measurement unit 42: Current value determination and analysis unit 43: Signal line (droplet sensor output signal) 44: Signal line (humidity sensor signal) 45: Signal line (temperature signal) 46: Output line 101: Evaporation measurement device

Claims

1. An evaporation measurement sensor having a structure in which a first thin-wire electrode made of a material containing at least one of a first metal and carbon and a second thin-wire electrode made of a material containing a second metal different from the first metal are alternately arranged in at least a portion of a region on a substrate having at least an insulating surface.

2. An transpiration measuring device for measuring transpiration from an object to be measured, comprising a sensor having a structure in which a first thin-wire electrode made of a material containing at least one of a first metal and carbon and a second thin-wire electrode made of a material containing a second metal different from the first metal are alternately arranged in at least a portion of a substrate, at least the surface of which is insulating, and a signal processing device for measuring the current flowing between the first thin-wire electrode and the second thin-wire electrode.

3. The transpiration measuring device according to claim 2, wherein the transpiration is a transpiration rate.

4. The transpiration measuring device according to claim 2 or 3, wherein the distance between said first thin wire electrode and said second thin wire electrode is constant in said region.

5. The transpiration measuring device according to claim 4, wherein the interval is not less than 100 nm and not more than 10 μm.

6. The transpiration measuring device according to any one of claims 2 to 5, wherein the first metal is selected from the group consisting of gold, platinum, silver, titanium and alloys thereof.

7. The transpiration measuring device according to any one of claims 2 to 6, wherein the material containing the second metal is selected from the group consisting of silver, copper, iron, zinc, nickel, cobalt, aluminum, tin, chromium, molybdenum, manganese, magnesium and alloys thereof.

8. An evaporative emission measuring device as described in any one of claims 2 to 7, wherein at least one of the first thin-wire electrode and the second thin-wire electrode is provided in a plurality of wires, and the first thin-wire electrode and the second thin-wire electrode extend from opposing directions toward each other, thereby running parallel to each other.

9. The transpiration measuring device according to any one of claims 2 to 8, wherein the object to be measured is a plant.

10. A method for measuring transpiration using the transpiration measuring device according to any one of claims 2 to 8, for measuring at least one of the amount and rate of transpiration from an object to be measured.

11. A step of preparing a humidity sensor and a galvanic current detection type droplet sensor; a step of placing the humidity sensor in an experimental environment with a relative humidity of 100% or less and acquiring output data from the humidity sensor under a plurality of conditions with different humidity and temperature to measure the change in relative humidity in the experimental environment; a step of calculating absolute humidity from the relative humidity and the temperature; a step of acquiring teacher data consisting of data on the rate of change in the amount of water vapor in the experimental environment based on the data on the change in absolute humidity; a step of placing the droplet sensor in a measurement environment and acquiring output data from the droplet sensor in the measurement environment; a step of comparing the teacher data and the output data of the droplet sensor to determine a correlation; a step of calculating a conversion coefficient α for converting an output value P of the droplet sensor into a rate of change S of the amount of water vapor in the measurement environment from a slope of the output data of the droplet sensor for which a correlation between the teacher data and the output data of the droplet sensor has been found; and a step of placing the droplet sensor in the measurement environment of the object to be measured and calculating the output P of the droplet sensor. ｍｅａｓｕｒｅ and a step of determining S ｍｅａｓｕｒｅ = α × P ｍｅａｓｕｒｅ from the evaporation rate S of the object to be measured ｍｅａｓｕｒｅ The transpiration measuring method for measuring the transpiration rate from the object to be measured comprises the step of determining 12. The transpiration measuring method according to claim 11, wherein the method for determining the correlation is one selected from the group consisting of regression analysis, t-test, and z-test.

13. According to the evaporation measurement method of claim 11 or 12, the evaporation rate S using the droplet sensor in the measurement target environment of the object to be measured is measured. ｍｅａｓｕｒｅ A step of continuously measuring the transpiration rate S for a period of time equal to or longer than a predetermined period of time t; ｍｅａｓｕｒｅ and calculating an amount of evaporation V at the predetermined time t by time-integrating the above-mentioned amount of evaporation V over the predetermined time t.

14. An evaporation measurement method according to any one of claims 11 to 13, wherein the droplet sensor has a structure in which a first thin wire electrode made of a material containing at least one of a first metal and carbon and a second thin wire electrode made of a material containing a second metal different from the first metal are alternately arranged in at least a portion of a region on a substrate having at least an insulating surface.

15. A method for measuring transpiration, comprising: a space consisting of a colony region in which a plurality of transpiration bodies emitting water vapor are clustered; and a blank region in which no transpiration bodies are present; forming an enclosed space isolated from the outside air; and installing at least one droplet sensor in the colony region and at least one in the blank region, and performing measurement using the transpiration measurement method according to any one of claims 11 to 14.

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