JP6784459B2 - Non-destructive, continuous, automatic measurement Peltier thermocouple cyclometer - Google Patents

Description

The production of high sugar content melons and high sugar content tomatoes is said to be cultivated under stress (also called water potential). In soil cultivation, irrigation is avoided and drainage is performed. In hydroponics, salt NaCl is mixed and rooted. Growing with regional stress. However, the current situation is that we have never seen non-destructive, continuous, and automatic measurement data for crop stress and soil stress, and no one could measure it.

The present invention provides a Perthia-type thermocouple cyclometer that non-destructively, continuously, and automatically measures stress on crops such as leaves, stems, roots, and fruits, and stress in soil, and is a medical treatment that measures the osmotic pressure of a solution. It can also be used as a related steam pressure osmotic meter.

High-quality cultivation that produces high sugar content melons, tomatoes, and strawberries requires cultivation management based on the biological information of the crop, but since no one could measure it so far, it relied on the intuition and experience of farmers. However, the TPP has intensified competition in agriculture in the global society, and the production of value-added agricultural products is required, and the development of rational next-generation agricultural technology based on data is desired.

In the present invention, the crop water potential (crop stress), which indicates the degree to which a crop sucks water, is indicated by an energy value, and the total water potential of soil (matric), which indicates the force of binding soil particles and soil water by an energy value. (Indicated by the sum of potential + permeation potential + gravitational potential) and the permeation potential indicating the osmotic pressure of the solution are measured, and the measured value is a negative value and is usually displayed in MPa units.

As detailed in his book (1995) by Boyer, there are two methods for direct measurement of crop stress (water potential): the pressure chamber method and the thermocouple cyclometer method. In Japan, the pressure chamber method of cutting and measuring leaves has been widely used because it is simple and easy to handle, but since the leaves are cut and measured with petioles, the number of settled leaves gradually decreases, which is fatal and continuous measurement is not possible. There was a drawback.

On the other hand, the thermocouple cyclometer method for obtaining the water potential by measuring the relative humidity in the chamber equilibrated with the water vapor pressure of the measurement sample is an accurate measurement method, but has many problems.

Commercially available American cyclometers are manually operated measuring instruments, and (1) the manual operation measuring procedure is complicated, and (2) the electromotive force where the movement of the meter needle on the measuring instrument is stagnant is visually observed. It is read, but the reading is unstable and unclear. (3) The read electromotive force is substituted into the calibration curve created in advance to calculate the water potential value, but it cannot be displayed directly quickly (. Many cyclometers (estimated about 15,000) were imported in the 1970s because 4) temperature fluctuations during measurement give measurement errors, and (5) it takes a long time to balance the vapor pressure with the sample. Nevertheless, it was rarely used in Japan.

Actual use of the thermocouple psychrometer is only seen in a few cases paper was stuffed with soil and cut leaves collected at constant greenhouse in the sample chamber and measuring the water potential, crops with onsite field There are no reports of non-destructive continuous measurements of water potential in the body or soil. Thus, thermocouple cyclometers have been abandoned for more than half a century because they have been judged unsuitable for on-site measurements with temperature fluctuations.

In addition, the 45-page measurement manual for commercial cyclometers uses the cyclometer method to measure the inflection point electromotive force, which indicates the dew point temperature corresponding to the dry-wet temperature difference, and the intermittent time-division current to bring the wet contact to the dew point temperature. Although it introduces the high-gromometer method that keeps it constant, most of the pages recommend the high-gromometer method from beginning to end with the explanation of the high-gromometer method, and the explanation of the cyclometer method is only 10 lines. The hygrometer method is an excellent measurement method with an advanced circuit that allows intermittent current to flow in a timely manner in order to keep the dew point temperature constant, but it is necessary to set an intermittent coefficient Πv that depends on the temperature, and in a constant temperature room. Limited to exams. On the other hand, the cyclometer method is convenient because it presents a temperature compensation formula for measured values and can be used in a field where the temperature changes , but it was not understood by general users.

Therefore, all domestic literature on water stress measurement of crops proposes indirect measurement methods as shown in the following reference, and finally the measured values by the pressure chamber method (Kibe water potential instead of leaf potential). The water potential is indirectly calculated from the calibration curve obtained from the correlation with (called).

JP-A-9-2819 JP 2001-272373 JP 2002-122646 JP-A-2005-308733 JP-A-2009-109363 JP 2006-67954 Patent Publication 2009-95344 Patent publication 2012-225736

The method for determining water stress of crops in Patent Document 1 discloses a method for determining water stress by the ratio of ¹³ C and ¹² C isotopes, but since a radioisotope is used, it is used in the field (field). It cannot be measured safely and easily.

The method for diagnosing water stress in a crop body of Patent Document 2 discloses a method in which a non-polarizing electrode is attached to the crop body and the soil to measure water stress by the potential difference between the two poles, but the type of crop, soil type, and soil. The electrical output varies greatly depending on the water content, leaving doubts about measurement accuracy.

The stress response measurement and device for crops in Patent Document 3 is a surface coil type resonator that irradiates a magnetic field generator and microwaves for measurement, and a non-destructive crop sample is placed in a space corresponding to the stress response of the crop. It is a method of observing the behavior of free radicals and active oxygen generated as a result of stress response, but the absolute water stress (water potential) is absolute just by looking at the change over time in the signal intensity of the relative unit with respect to the stress of the crop body. No evaluation has been done.

As a method for measuring the stress received by a crop in Patent Document 4, a method for evaluating water stress from the spectral reflectance characteristics reflected from green leaves and a standard white plate is disclosed, and the reflected light and transmitted light are separated to a wavelength of 500 to 800 nm. Spectral reflectance is calculated for continuous wavelengths, the wavelength range in which it rises sharply is obtained, and water stress is evaluated from the transition of the central wavelength in that wavelength range, but an expensive spectroscope is required and the accuracy is high. It is described in Japanese Patent Application Laid-Open No. 2009-109363 that the inventor himself subsequently submitted that it was not sufficient.

In the water stress measurement method and apparatus for crops of Patent Document 5, the water stress is calculated from the multivariate analysis method using the spectral characteristic value at an arbitrary time point as a variable, but the water potential of the leaves actually measured by the pressure chamber method is used as a reference. It must be entered as a value, and the accuracy is poor because the water stress cannot be evaluated by the measuring instrument alone.

In the method for measuring the adaptive response response of a crop body to stress in Patent Document 6, the crop body is irradiated with a microwave, the complex permittivity ε is obtained from the signal reflected from the crop body, and the complex permittivity ε is obtained from the frequency characteristics of the complex permittivity ε. Although the stress adaptation response applied to the crop body is detected, it is not possible to obtain an absolute measured value only by measuring the relative fluctuation.

The adaptive response measuring device for the crop body and the adaptive response measuring method for the crop body of Patent Document 7 were devised by the inventor of Patent Document 6 on an extension line thereof, and the first electrode and the first electrode and the first electrode and the first electrode and the first The two electrodes are arranged with a gap between them, a predetermined electric signal is applied to the electrodes, and the characteristics of the applied electric signal are measured to measure the stress response of the crop body, but the measured data is It is complicated and cannot be analyzed.

The water potential measuring method and the water potential measuring device of Patent Document 8 are for immersing a leaf section of a crop in a different fluorescent reagent solution for 1 hour and obtaining the water potential of a sample from the brightness of the fluorescent image. It is necessary to find the correlation between the water potential value of the pressure chamber method and the brightness, and it cannot be said that this is a rapid measurement method.

As described above, the domestic literature indirectly measures the water stress of crops, while the foreign literature relates to the thermocouple cyclometer method, which is a direct measurement method, as can be seen in the following reference. More than 20 years have already passed.
USA Patent 3,739,629 USA Patent 3,831,435 USA Patent 4,242,906 USA patent 4,952,071

Patent Document 8 of 1973 is a measurement in which a measurement sample is packed in a small sample chamber, inserted into a sample holder, sealed, and the water potential is obtained from the relative humidity in the sample chamber balanced with the water vapor pressure of the measurement sample. The method is described, and the commercialized products of this patent are the sample chamber C-51 manufactured by WESCO, which is commercially available, and the dew point microvolt meter HR-33 having a circuit for maintaining the dew point. However, WESCO's products recommend a high-glometer method that can maintain a constant dew point temperature on the thermocouple when the room temperature is constant, and do not recommend measurement in fields where the temperature fluctuates.

Patent Document 9 of 1974 proposes a small thermocouple sensor composed of a silver foil having a thickness of 50 microns that nondestructively measures the water potential of a leaf, and is characterized by being easily attached to a leaf. However, since only the wet contact in the chamber of the thermocouple sensor is measured and the temperature inside the chamber is not measured, the temperature cannot be corrected, which causes an error.

Patent Document 10 of 1981 proposes a hygrometer and a cyclometer for soil having a structure for protecting a thermocouple with a sealing material that allows water vapor to pass through, and is commercially available as a sensor for PT-51 soil manufactured by WESCO. However, soil salts accumulate in the ceramic cup used as a sealing material, which affects the measurement, and the large space inside the chamber requires an equilibrium time of 3 to 5 hours, resulting in rapid water potential due to irrigation, etc. It cannot handle the measurement of fluctuations.

Patent Document 11 of 1990 discloses a cyclometer capable of measuring a large number of points by switching with a switch, but it is natural that a large number of points are manually sequentially measured with a changeover switch.

As described above, the thermocouple cyclometer method has been widely used in other countries as a measurement method that can directly measure the water potential of crops and soil, and many papers have been reported, but on-site measurement is impossible in Japan. It was judged and never used.

In the present invention, a Peltier-type thermocouple cyclometer was newly manufactured without imitating a foreign product, and its measurement accuracy and reproducibility were examined in detail. As a result, we have realized a non-destructive, continuous, automatic, and on-site measurement Peltier thermocouple cyclometer that can be directly digitally displayed in real time in a field where temperature changes are drastic .

The principle of measuring water potential by the cyclometer method is the chemical potential value (MPa unit) calculated from the Kelvin formula below by obtaining the relative humidity from the temperature difference between the dry and wet bulbs in the chamber where the vapor pressure is balanced with the measurement sample. It is an absolute value.
Water stress Ψ = energy / volume = RT / V ・ lm (P / Po)
Here, R: gas constant, T: absolute temperature, V: molar volume of water, P / Po: relative humidity.

The Pertier-type cyclometer developed by Spanner (1951) first offsets the Seebeck electromotive force of the thermocouple balanced with the temperature in the chamber to 0 μV, and then conversely, when a current is passed, the thermocouple contact becomes a dew point due to the Pertier effect. It is cooled below and dew condensation water adheres, but when the energization is stopped, it is restored to the original 0 μV by vaporization of the dew condensation water. In the restoration process, the turning point electromotive force Vd at which the flat signal that slowly rises due to the vaporization of condensed water starts is exactly the dew point temperature, that is, the water potential can be measured because it corresponds to the temperature difference of the wet and dry bulbs. This is an epoch-making method that can automatically measure the temperature while saving time and effort as compared with the Richard type cyclometer that measures by dropping water droplets on the wet contact point.

However, although the Peltier thermocouple cyclometer is an established measurement method in principle, it cannot clearly and automatically read the measured values for the measurement data, and the cooling current and cooling time cannot be set appropriately. Since the temperature correction formula is not clear and the calibration curve test is unclear, it has hindered the improvement of measurement accuracy and automatic measurement of the Peltier thermocouple cyclometer.

In order to solve these problems, the present invention manufactures a measuring instrument body of a Peltier type thermocouple cyclometer from the beginning without relying on a commercially available product made in the United States, and connects it to a personal computer and a thermocouple sensor. , The measurement characteristics were examined in detail. As a result, when the development of the automatic reading software of the turning point electromotive force Vd indicating the dew point temperature described in claim 1 and the appropriate cooling current and cooling time for each sensor described in claim 2 are set and measured. the introduction of each of the sensor temperature correction formula, the introduction of 25 ° C. calibration curve of each sensor according to claim 3, allowing the automatic measurement of the intense field of measurement accuracy improved and temperature fluctuations. Also, the soil attachment according to claim 5 leaf attachment of claim 4, rather than the measured article is come collected from the field, measured as is in situ against the sensor to the measuring article It can be made, to achieve a time saving and non-destructive measurement of the vapor pressure equilibrium.

This enables non-destructive and continuous on-site measurement with severe temperature fluctuations, which enables direct digital display of the water potential of crop leaves by simply inserting a sensor between the leaves and the water potential of the soil in real time by simply inserting the sensor into the soil.・ Realized an automatic measurement cyclometer.

In consideration of the measurement accuracy and convenience of the measuring instrument, the present invention reasonably and automatically reads (1) the measurement operation is fully automated by a personal computer, and (2) the turning point electromotive force Vd indicating the dew point temperature is read. We have developed program software for personal computers, (3) created a temperature compensation formula for each sensor that obtains an electromotive force V ₂₅ converted to 25 ° C so that on-site measurement with temperature changes can be performed, and (4) wet contacts are sufficient so far. Reproducibility was ensured by setting appropriate values for each sensor and measuring the cooling current and cooling time, which had been appropriately treated as dew condensation. (5) Groove depth of the concave groove chamber of the thermocouple sensor The chamber capacity is reduced to 2 mm or less, the thermocouple sensor is brought into direct contact with the measurement target to shorten the vapor pressure equilibrium time, and the leaves are not cut and the soil is not collected. It enables measurement in the state. (6) Since the personal computer directly calculates and displays the water potential value from the 25 ° C calibration line for each sensor obtained in advance, it is possible to grasp the water potential of crops and soil in real time. It became so.

The automatic measurement cyclometers reported so far in research papers do not read the true inflection point electromotive force Vd, but the thermocouple electromotive force 2.4 seconds or 5 seconds after a certain period of time after the power is stopped. Since the value V was easily read, not only was it unreasonable, but the measurement accuracy was extremely poor. In this patent, since the true inflection point electromotive force Vd is read by the automatic reading analysis software for personal computers developed as shown in claim 1, an accurate water potential value can be calculated, and the water potential value is reproducible and highly accurate. Automatic measurement is now possible.

So far, many papers relative to the temperature correction formula is the temperature measurement range is reported limiting linear regression equation, a wide range of temperature correction formula for temperature range quadratic regression equation was determined accordingly to claim 2 Correlated with. It is considered that the reason why the result is different from the conventional result is that the reading of the inflection point electromotive force Vd in claim 1 is accurate.

For the calibration lines so far, a linear regression equation correlated using five kinds of NaCl solutions having a concentration of 0.05 mol, 0.1 mol, 0.3 mol, 0.5 mol, and 1 mol has been proposed. However, the calibration lines performed in the present invention are distilled water, 0.01 mol, 0.02 mol, 0.03 mol, 0.05 mol, 0.07 mol, 0.1 mol, 0.2 mol, 0. .3 mol, 0.5 mol, 0.7 mol, 1 mol, 1.5 mol, 2 mol, relapsed using 14 broad concentrations of NaCl solution, measured 25 ° C. variation It was correlated relationship between TenOkoshi power Vd ₂₅ and the known 25 ° C. osmolality [psi _25, 25 ° C. calibration curve specific to each sensor as described in claim 3 is obtained, et al. This is also a new finding that has never existed before.

The reason why the vapor pressure equilibrium took a long time in the conventional commercially available measuring instruments was that the soil and cut leaves to be measured were packed in a large container for measurement, but in this patent, claims 4 and 5 Since the thermocouple sensor with a small concave groove chamber is directly pressed against the measurement target using the attachment for measurement, the vapor pressure equilibrium time is shortened because the internal volume of the chamber is small, and non-destructive measurement is possible. Real-time measurement with fast responsiveness has become possible .

Further, the automatic analysis software for a personal computer that reads the true inflection point electromotive force Vd according to claim 1 will be described in detail. The measurement principle of the Peltier thermocouple cyclometer is to offset the thermocouple electromotive force of the wet contact in the chamber of the thermocouple sensor balanced with the water vapor pressure of the measurement sample to 0 μV, and then adjust the thermocouple of this wet contact. A reverse current is passed through the pair to cool the wet contact below the dew point by the Peltier effect to cause dew condensation, the dew point temperature is detected from the fluctuation of the thermocouple electromotive force V of the wet contact after the energization is stopped, and the water potential is detected from the relative humidity. Is calculated and calculated.

In other words, the Pertier effect caused by passing a reverse current through the thermocouple in the chamber cools the thermocouple contact below the dew point and condenses the water droplets in the air inside the chamber, and when the energization is stopped, the water droplets evaporate and cool. Restore to the previous temperature. When the electromotive force of this restoration process is recorded, the time gradient is clearly different between the vaporization process of the condensed water and the restoration process to the previous temperature, and the voltage rise due to the power stop overshoots and then rises sharply. The fluctuation of the wet contact electromotive force in the process of vaporizing the condensed water shows a slow flat signal, and then it is restored to 0 μV before cooling by the heat inflow from the reference contact at the base of the wet contact. Since the starting point of the flat signal is the dew point temperature, the inflection point electromotive force Vd is carefully read, and the relative humidity is obtained from this dew point temperature to calculate the water potential.

However, accurate reading of this inflection point has conventionally required complicated work of reading by measuring with a measuring rod on analog recording paper. In other words, a ruler was applied to the straight line part of the flat signal, and the point where the curve was separated from the straight line was carefully read, but there was a reading error by the measurer, and the water potential could not be displayed directly. Further, in the conventional analog measuring instrument, even if the same sensor is used to repeatedly measure the solution of the same concentration, the appearance after the energization is stopped is completely different, and the inflection point electromotive force Vd is also completely different. The cooling time for the thermocouple sensor seems to have deteriorated in reproducibility due to the ambiguous time setting . In order to improve reproducibility, it is necessary to fix and measure the appropriate cooling current and cooling time.

As a result of verifying more than 5,000 raw data measured by fixing the cooling current and cooling time to appropriate values using a newly manufactured Peltier thermocouple cyclometer.
The fluctuation of the thermoelectric electromotive force V of the wet contact after the cooling energization is stopped is changed every minute time Δt seconds V ₁ , V ₂ , V ₃ , V ₄ , ... Vn, Vn _{+ 1} , Vn ₊₂ , ... when ... and digitally recorded, the time difference [delta] V / delta] t of the thermoelectric TaiOkoshi power V of each delta] t seconds is defined as ΔVn = Vn-Vn _+1, Δt seconds every second order time differential Δ ² V / Δt ² When is defined as ΔΔVn = ΔVn−ΔVn _{+ 1} , the turning point electromotive force at the time of proper cooling is the V value at which Δ ² V / Δt ² ≧ 0 first, and the turning point electromotive force at the time of overcooling. The power is the rebound V value at which ΔV / Δt ≧ 0 first, and as a whole, automatic analysis program software that adopts the V value at the earlier time or the V value at the same time as the turning point electromotive force Vd is used. Now that you have created, it was Tsu name so that it can be read automatically.

In the thermocouple cyclometer method, the measurement accuracy has been questioned due to the error caused by the fluctuation of the ambient temperature during measurement, and it has been considered impossible to perform on-site measurement. However, the turning point electromotive force Vd is within 1 second after the energization is stopped. Even if the existing cooling time of 15 seconds, which is normally set, is added up, the measurement is completed in 16 seconds. Therefore, the influence of temperature fluctuation during one measurement can be almost ignored.

The ultimate goal of the present invention is to provide a measuring instrument that allows anyone to easily measure the water potential of a crop or soil in the field with high accuracy and speed. Therefore, by using the leaf attachment and soil leaf attachment according to claims 4 and 5, simply sandwiching the thermocouple sensor between the leaves or inserting the thermocouple sensor into the soil is sufficient to water the leaves and soil. It was realized a non-destructive measurement of potential. By collecting basic data in fields where high sugar content tomatoes and high sugar content melons are cultivated, we will establish rational cultivation techniques based on the data and develop economically beneficial agriculture by producing value-added fruits and vegetables . To.

In order to achieve that goal, a series of complicated measurement operations are automatically performed by a personal computer (microcomputer), and the newly developed automatic reading analysis program software described in claim 1 automatically records the wet contact digitally. The water potential (water stress) Ψ ₂₅ is quickly calculated from the turning point electromotive force Vd read instantly and accurately from the power data, the temperature T of the dry contact, and the 25 ° C calibration curve obtained in advance, and is directly digitalized. A non-destructive, continuous, and automatic measurement cyclometer that can be displayed was absolutely necessary. The introduction of the temperature compensation type and the 25 ° C. calibration curve type according to claims 2 and 3 has made it possible to obtain highly accurate water potential measurement.

FIG. 1 is a schematic view of a 1-channel Peltier thermocouple cyclometer having one measurement point. It is composed of a cyclometer measuring instrument main body 3, a thermocouple sensor 5, and a personal computer 1, each of which is composed of a cyclometer measuring instrument main body 3. It is connected by the sensor connection cable 4 and the communication USB cable 2. The multi-channel thermocouple cyclometer that can measure a large number of points at the same time is further loaded with a scanner circuit, and the thermocouple cyclometer for 8 channels has already been completed. However, in the present invention, a simple one-channel thermocouple is used. explain.

The cyclometer measuring instrument main body 3 uses a semiconductor chip such as a μ controller, a D / A converter, and a tens of bits ΣΔA / D converter, and uses a head amplifier amplifier circuit, a minute voltage measurement circuit, a constant current generation circuit, and a thermocouple. It constitutes a temperature measurement circuit, etc.

The thermocouple sensor 5 of FIG. 2 has two thermocouple contacts, a T-type dry contact thermocouple 9 for temperature measurement and an E-type wet contact thermocouple 8 for dew point measurement, built in the concave chamber.

The personal computer 1 of FIG. 1 automatically measures and operates the thermocouple sensor 5 via the cyclometer measuring instrument main body 3, and of the E-type wet contact thermocouple 8 for measuring the temperature and dew point of the T-type dry contact thermocouple 9. The electromotive force fluctuation is automatically recorded digitally, and the turning point electromotive force Vd indicating the dew point temperature is automatically read by the analysis program software for the electromotive force fluctuation of the E-type wet contact thermocouple 8 for dew point measurement.

The non-destructive, continuous, and automatic measurement Peltier type thermocouple cyclometer is a constant digital measurement record of the temperature by the T-type dry contact thermocouple 9 in the concave chamber, and 0 point adjustment of the electromotive force in the E type wet contact thermocouple 8. Cooling below the dew point temperature due to the Pertier effect by energizing the E-type wet contact thermocouple 8, stopping the energization of the E-type wet contact thermocouple 8 after dew condensation, restoration process in which the condensed water begins to vaporize and restores to the temperature before cooling Digital recording of the electromotive force change of the E-type wet contact thermocouple 8 and automatic reading of the electromotive force Vd at the turning point according to claim 1 on the digital recording data of the E-type wet contact thermocouple 8; Calculated from the 25 ° C electromotive force V ₂₅ converted by the temperature correction formula according to claim 2 from the power Vd and the measured temperature T of the T-type dry contact thermocouple 9 and the 25 ° C calibration line according to claim 3. that 25 ° C. water potential values [psi ₂₅ of the digital display has, this series of complicated measuring procedure, digital recording, treated briefly with the analysis and calculation and display personal computer 1 (microcomputer) controls operations. Furthermore, by performing one measurement time as quickly as several tens of seconds or less, it was possible to reduce the measurement error due to fluctuations in the ambient temperature during one measurement . The configuration of the present application is, for the final purpose, from the automatic reading of the turning point electromotive force Vd indicating the dew point temperature according to claim 1, the temperature correction formula according to claim 2, and the 25 ° C. calibration curve according to claim 3. It is characterized in that the water potential value Ψ ₂₅ of a certain measurement sample 10 is directly calculated and displayed.

FIG. 2 shows a thermocouple sensor 5 for measuring water potential. Based on a circular Teflon rod 7 having an outer diameter of 8.8 mm and a length of 15 mm, a groove having an inner diameter of 5.2 mm and a depth of 1 mm is cut at the tip. Create a small cylindrical concave groove chamber. In addition, three round holes are drilled in the cylindrical concave groove, but in order to arrange the contact of the E-type wet contact thermocouple 8 for dew point measurement in the center of the concave groove, it is in the 3 o'clock direction and the 9 o'clock direction of the watch. , Two Φ1.5 mm round holes with a center-to-center distance of 3.5 mm, and one Φ1.5 mm round hole for installing a T-type dry contact thermocouple 9 for temperature measurement at 6 o'clock. Open with a drill. On the outer circumference of the circular Teflon rod 7, a stainless steel cylindrical protective tube 6 having a length of 23 mm, an inner diameter of 9 mm, and an outer diameter of 10 mm is fixed with an epoxy adhesive 19 with the tips aligned. (Teflon is a registered trademark of EI Deyupon Do Nemours & Company.)

The E-type wet contact thermocouple 8 for measuring the dew point has a 20 mm long, Φ1 mm thermocouple base copper wire 18 inserted in two round holes in the 3 o'clock direction and the 9 o'clock direction, and the outer circumference is covered with an epoxy adhesive 19. It is fixed, but the upper ends of the two thermocouple base copper wires 18 are fixed so as not to protrude into the recessed groove chamber. Then, after welding the Φ25 μm chromel wire 20 and the Φ25 μm constantan wire 21 to the upper end surface of each thermocouple base copper wire 18, the ultrafine wires of the Φ25 μm chromel wire 20 and the Φ25 μm constantan wire 21 are further welded to measure the dew point. E-type wet contact thermocouple 8 for use is formed. The contact height of the E-type thermocouple is set to about 0.5 mm in order to center the concave groove depth of 1 mm. A 0.3 SQ (cross-sectional area of about 0.3 mm ² ) 2-core copper wire shielded wire 22 having a length of 10 m is connected to the lower end of the base copper wire 18 of the two E-type wet contact thermocouples.

The T-type dry contact thermocouple 9 for temperature measurement, in which the tips of the Φ0.5 mm copper wire and the Φ0.5 mm constantan wire are soldered, is inserted into the Φ1.5 mm hole opened at 6 o'clock, and the outer circumference is epoxy. It is fixed with the adhesive 19, but the bare contact of the T-type thermocouple at the tip is slightly exposed on the surface of the concave groove chamber and fixed. The length of the T-type thermocouple of the copper wire and the constantan wire is also 10 m.

The sensor connection cable 4 consists of a 0.3SQ 2-core copper wire shielded wire 22 connected to an E-type wet contact thermocouple and a Φ0.5 mm copper-constantan wire constituting a T-type dry contact thermocouple, each having a length of 10 m. Cut and align and fasten in places with shrink tubes. A total of five connectors, two 2-core copper wires, one shielded wire, and one copper-constantan wire, are connected to the connector 23 connected to the cyclometer measuring instrument main body 3.

As described in claim 1, the most important task in the measurement of the Peltier thermocouple cyclometer is the accurate automatic reading of the dew point temperature obtained as the measured value.

In the measurement of the Peltier thermocouple cyclometer, the thermocouple electromotive force V due to the Seebeck effect of the wet contact that is balanced with the temperature in the concave chamber is first offset to 0 μV, and then when a reverse current is applied, it is cooled by the Peltier effect. Condensation forms on the wet contacts, but when the energization is stopped after the dew condensation, the fluctuation of the negative thermocouple electromotive force V of the wet contacts first rises sharply due to the stop of energization, and then the temperature rises slowly due to the vaporization of the condensed water. A flat signal is shown, followed by a restoration curve where the initial offset voltage rises to 0 μV due to the inflow of heat from the reference contact.

In this restoration curve, the inflection point electromotive force Vd at which the flat signal that slowly rises due to the vaporization of condensed water starts is exactly the dew point temperature, that is, corresponds to the temperature difference of the wet and dry bulbs.

The inflection point of the curve is the point where the gradient of change does not change, and mathematically it is the point of the second-order differential Δ ² V / Δt ² = 0, but this is because the thermoelectric pair contact point is in the center of the spherical space and the contact point. In the ideal state where the above condensed water absorbs heat from all directions of the surrounding air and vaporizes, the wet contact is actually placed in the center of the concave groove chamber of a cylindrical space with a diameter of 5.2 mm and a depth of 1 mm. It is very different from the conditions.

In this instrument, it is important to reasonably find inflection point electromotive force Vd from variation data thermoelectric TaiOkoshi power V to be measured, a negative thermoelectric TaiOkoshi power cooling deenergized after the E-type wet contact 8 When the fluctuation of V is digitally recorded every 0.1 seconds of a minute time, the column of electromotive force V in FIGS. 13 and 14 is described as V _0.1 , V _0.2 , V _0.3 , V _0.4 .... .. The column of the time difference ΔV every 0.1 seconds is calculated as ΔV _0.1 = V _0.1 −V _0.2 , ΔV _0.2 = V _0.2 −V _0.3 , ΔV _0.3 = V _0.3 −V _0.4 , and so on. The column of ΔΔV of the second-order time difference every second is calculated as ΔΔV _0.1 = ΔV _0.1 −ΔV _0.2 , ΔΔV _0.2 = ΔV _0.2 −ΔV _0.3 , ΔΔV _0.3 = ΔV _0.3 − ΔV _0.4 , and so on. As a result of examining a large number of actually measured data of more than 5,000, the inflection point electromotive force at the time of proper cooling is the V value at which ΔΔV ≧ 0 at first (Fig. 13), and the inflection point electromotive force at the time of overcooling. Is the rebound V value at which ΔV ≧ 0 at first (Fig. 14), and as a whole, the V value at the earlier time of both or the V value at the same time of both is the inflection point electromotive force Vd. I created a program software for a personal computer that automatically reads as . As a result , the inflection point electromotive force Vd indicating the dew point temperature could be accurately read for all the measured data.

In FIG. 13, after cooling the wet contact with a cooling current of 7 mA and a cooling time of 15 seconds with respect to a 1 mol solution of NaCl, the electromotive force V of the E-type wet contact thermocouple 8 after the energization is stopped is applied every 0.1 seconds. Although it is displayed, since ΔV in FIG. 13 is the amount of change in V, the value obtained by subtracting V in the second row from V in the first row is entered as ΔV in the first row, and ΔΔV in FIG. 13 is ΔV. Since it is the change gradient of, the value obtained by subtracting the ΔV of the second line from the ΔV of the first line is entered as the ΔΔV of the first line, and the subsequent values are similarly calculated sequentially. In normal processing, the value obtained by subtracting the second line from the first line is entered as the forward difference in the second line, but in the present invention, the reason why the value is intentionally entered in the first line and used as the backward difference is that the measured value to be obtained is a flat signal. Since it is the starting point of, in order to read the starting point of the change or the starting point of the change gradient, it is entered as the receding difference in the first line. After that, all the receding differences between ΔV and ΔΔV every 0.1 second are calculated and entered from the measured electromotive force V. As a result, in FIG. 13, 1.3 seconds after ΔV changes to positive 0.000 and 0.4 seconds after ΔΔV changes to positive 0.033 are regarded as inflection points, but as a whole, both are earlier in time. it is read electromotive force -19.120μV after 0.4 seconds as the variable KyokutenOkoshi power Vd during proper cooling, chamber temperature T at that time is 13.8 ° C..

FIG. 5 illustrates the fluctuation of the electromotive force of the E-type wet contact thermocouple 8 at the time of proper cooling with a cooling time of 15 seconds and a cooling current of 7 mA in FIG. 13, and shows a flat signal for a while after the inflection point marked with a white circle.

FIG. 14 shows the electromotive force V of the wet contact thermocouple after cooling the wet contact with a cooling current of 10 mA and a cooling time of 15 seconds for a 1 mol solution of NaCl every 0.1 seconds. However, when the electromotive forces V, ΔV, and ΔΔV are processed in the same manner as in FIG. 13, 0.1 seconds after ΔV changes to positive 0.073 and 0.1 seconds after ΔΔV changes to positive 0.449. is considered an inflection point, is read electromotive force -16.909μV of both at the same time 0.1 second after the whole variable KyokutenOkoshi power Vd during supercooling, the chamber temperature T at that time 13 It is 8.8 ° C.

In addition, 7mA 15 seconds, which can measure a NaCl-2 mol solution (-9,787 MPa osmotic pressure at 25 ° C), which is the maximum measurement range, was set as an appropriate cooling condition from FIG. 7, but since all the calibration curves are measured under the same cooling condition. Naturally, it will be supercooled for a solution with a low concentration. In the present invention, in consideration of this point, a program software for a personal computer that automatically reads measured values that can be applied to both proper cooling and supercooling has been created.

FIG. 6 illustrates the fluctuation of the electromotive force of the wet contact during supercooling with a cooling time of 15 seconds and a cooling current of 10 mA in FIG. 14, but the rebound value that overshoots and rises further after the power supply is stopped causes an inflection point. The electric power is Vd, and a flat signal is shown for a while after the inflection point marked with a white circle.

FIG. 7 illustrates the 25 ° C. turning point osmotic pressure Vd ₂₅ at each cooling current when the cooling time is fixed at 15 seconds for a 2 mol solution, a 1.5 mol solution, and a 1 mol solution of NaCl. However, the maximum concentration of NaCl-2 mol solution (-9.787 MPa osmotic pressure at 25 ° C.) cannot be measured unless a cooling current of 5.5 mA or more is applied. In order to obtain stable measurements for the three types of solution concentrations, a cooling current of 6 to 9 mA is required at a cooling time of 15 seconds, and in order to reduce supercooling in low-concentration solutions, a cooling time of 15 seconds is an appropriate cooling condition. , A cooling current of 7 mA was adopted.

However, although the thermocouple sensor is manufactured with the same specifications, the appearance of each sensor is different, and those that can measure up to 1 mol solution, those that can measure up to 1.5 mol solution, and those that can measure up to 2 mol solution. , And the characteristics of the measurement limit are different for each. It is presumed that this occurs because the contact size of the E-type wet contact thermocouple 8 with a diameter of 25 μm is slightly different, but it is necessary to investigate a sensor structure that has a wide measurement range and enables stable measurement.

FIG. 8 illustrates the relationship between each cooling time and the 25 ° C. turning point electromotive force Vd ₂₅ when the cooling current is fixed at 7 mA in a NaCl-1 mol solution (-4.644 MPa osmotic pressure at 25 ° C.). However, obviously, the longer the cooling time, the smaller the 25 ° C. turning point electromotive force Vd ₂₅ , and the conventional idea that the cooling conditions should be appropriate if the wet contacts are sufficiently cooled below the dew point temperature is denied. To. That is, in order to ensure reproducibility, it is necessary to always measure under the same cooling conditions, and as described in claim 3, the set values of the cooling current and the cooling time must be fixed and measured. As the cooling time, 15 seconds was adopted as an appropriate time from FIG.

Figure 9 is a 25 ° C. calibration curve in the case of cooling conditions 7mA15 seconds, penetration of distilled water 25 ° C. osmotic pressure [psi ₂₅ 14 type solutions of different concentrations of up to NaCl-2 moles (per mole concentration of NaCl at 25 ° C. pressure as viewed the relationship 25 ° C. HenkyokutenOkoshi power Vd ₂₅ to known) have been published, the generating method of a calibration curve according to claim 3 25 ° C. calibration curve Ψ _{25 = f} (V ₂₅ ² ) is obtained, et al. Since this 25 ° C. calibration curve is different for each sensor, it is necessary to obtain it in advance for each sensor .

For the conventional calibration curve, a linear regression equation correlated using five kinds of NaCl solutions having a concentration of 0.05 mol, 0.1 mol, 0.3 mol, 0.5 mol, and 1 mol has been proposed. It is true that even in FIG. 9, the 25 ° C. turning point electromotive force Vd ₂₅ decreases linearly with respect to the osmotic pressure up to the NaCl-1 molar concentration, but at the NaCl-1.5 molar concentration and the 2 molar concentration. The degree of decrease of the 25 ° C. turning point osmotic pressure Vd ₂₅ becomes slow, and the whole is returned by a quadratic curve formula including the NaCl −1.5 molar concentration and the 2 molar concentration. This is a quadratic regression curve formula because the measurement application range is expanded. Incidentally, the measurement value of 2.2 molar NaCl solution in the sensor of FIG. 9 (25 ° C. osmotic -10.887MPa) becomes a measurement outside disabled measurement becomes white circle, the measurement range of up to the 2 molar NaCl solution The calibration curve is expressed by the following equation. Ψ is, of course, the water potential Ψ ₂₅ at 25 ° C.
^{_{Ψ = -0.004428 · V 25 2 +0.1254}} · V 25 +0.275
Here, Ψ: water potential (MPa), V ₂₅ : 25 ° C conversion inflection point electromotive force (μV)

In FIG. 10, the chamber containing the thermocouple at the tip of the sensor was brought into close contact with a 1-molar NaCl solution, and continuous automatic measurement was performed throughout the day at a site where the temperature fluctuated. Correlated by the quadratic regression equation of the measured temperature T of the dry contact in the chamber, when T = 25 ° C is substituted, the 25 ° C inflection point electromotive force is V ₂₅ = -19.910 μV. Since the calibration curve is tested by the osmotic pressure of each concentration of NaCl at 25 ° C., similarly, based on the 25 ° C. turning point electromotive force Vd ₂₅ , the ratio Vd of the turning point electromotive force Vd to V ₂₅ is used. As shown in FIG. 11, / V ₂₅ depends on the temperature T and is correlated with the quadratic regression equation Vd / V ₂₅ = f (T ² ), and this regression equation is called a temperature correction equation. However, although sensors are manufactured with the same specifications, the temperature compensation type Vd / V ₂₅ = f (T ² ) is slightly different for each sensor, so it is necessary to obtain it for each sensor. Then, the temperature correction formula of the 1 molar concentration NaCl solution was adopted as a representative formula. The temperature compensation formula for the sensor in FIG. 11 is as follows.
Vd / V ₂₅ = 0.000453 · T ² + 0.0121 · T + 0.4136

From this, as described in claim 2, V ₂₅ = Vd / f (T ² ) obtained by converting the turning point electromotive force Vd of the wet contact and the temperature T of the dry contact by exchanging both terms of the temperature correction formula. by substituting calculate the 25 ° C. HenkyokutenOkoshi power _{Vd 25} to, is substituted further 25 ° C. calibration curve previously obtained for each sensor ^{_{Ψ 25 = f (V 25 2}} ), a measurement sample is the final purpose Ru determine the water potential value (osmotic value) Ψ _25. This has made it possible to perform on-site measurement with drastic temperature fluctuations.
Incidentally, the following equation is used for the temperature correction of the sensor in FIG.
V ₂₅ = Vd / (0.000453 · T ² + 0.0121 · T + 0.4136)

FIG. 12 shows a non-destructive, continuous, automatic, and on-site measurement in which the thermocouple sensor 5 inserted in the leaf attachment described in FIGS. 3 and 4 is attached to an eggplant leaf, and is measured continuously for 50 days. The water potential fluctuations of eggplant leaves for the first week of the above are illustrated. The fluctuation is greatly affected by the weather conditions, but the measurement at 10-minute intervals closely tracks the fluctuation of the water potential of the leaves.

FIG. 3 shows a leaf attachment for attaching the thermocouple sensor 5 to the back of the leaf of the crop leaf 11 in close contact with the aluminum storage tube 14 having an inner diameter of 10.1 mm, an outer diameter of 12 mm, and a length of 35 mm on the lower surface of the clothespin 12. Is fixed with the epoxy adhesive 19. The water potential of the crop leaf 11 is measured by inserting a thermocouple sensor 5 having an outer diameter of 10 mm and a length of 23 mm into the aluminum storage tube 14 and fixing it with vinyl tape or the like. Considering the physical damage of the crop leaf 11, the crop leaf 11 should be sandwiched by the force of the spring 13 of the clothespin 12, and is fixed by the lock rod 15 made of a toothpick for measurement.

FIG. 4 shows an attachment for soil for bringing the thermocouple sensor 5 into close contact with the soil 16. A stainless 200 mesh wire mesh is epoxy-bonded to the lower end of an aluminum storage tube 14 having an inner diameter of 10.1 mm, an outer diameter of 12 mm, and a length of 300 mm. It is fixed with agent 19, and a thermocouple sensor 5 having an outer diameter of 10 mm and a length of 23 mm is inserted from the upper end and fixed with vinyl tape to make it waterproof. The opening of the concave chamber of the thermocouple sensor 5 is brought into close contact with the measurement soil 16 via a stainless steel 200 mesh wire mesh to measure the soil moisture potential.

Peltier type cyclometer measurement system Cross section and top view of thermocouple sensor Cross-sectional view of the leaf measurement attachment Sectional view of attachment for soil measurement Fluctuation of electromotive force of wet contact thermocouple after cooling current is stopped (at the time of proper cooling) Fluctuation of electromotive force of wet contact thermocouple after cooling current stop (during supercooling) Measured value characteristics by cooling current Measured value characteristics by cooling time Calibration curve (when cooling condition is 7mA for 15 seconds) Relationship between measured temperature T and inflection point electromotive force Vd Temperature compensation type Daily variation of water potential of eggplant leaves Electromotive force fluctuation in NaCl-1 mol solution (in the case of proper cooling) Electromotive force fluctuation in NaCl-1 mol solution (in the case of supercooling)

1 PC 2 Communication USB cable 3 Cyclometer measuring instrument body 4 Sensor connection cable 5 Thermocouple sensor 6 Stainless steel cylindrical protective tube 7 Circular Teflon rod 8 E-type wet contact thermocouple for dew point measurement 9 T-type dry for temperature measurement Contact thermocouple 10 Measurement data 11 Crop leaf 12 Washing scissors 13 Spring 14 Aluminum storage tube 15 Lock rod 16 Soil 17 Stainless steel wire mesh 18 Thermocouple base Copper wire 19 Epoxy adhesive 20 Φ25 μm Chromel wire 21 Φ25 μm Constantan wire 22 0.3SQ 2 cores Copper wire shielded wire 23 connector

Claims (5)

The opening of the concave chamber is pressed against the measurement sample to bring it into close contact with the measurement sample, and two thermocouples, a dry contact for measuring the temperature T in the concave chamber and a wet contact for measuring the dew point temperature, are built in the concave chamber. When connecting the sensor to the main body of the cyclometer measuring instrument with a sensor connection cable and connecting the main body of the cyclometer measuring instrument to a personal computer with a USB communication cable,
In a Peltier thermocouple cyclometer that controls a series of measurement procedures with this personal computer, automatically records digital measurement values, and calculates and displays the water potential of the measurement sample.
As the measurement procedure, the thermocouple electromotive force V due to the Seebeck effect of the wet contact, which is in equilibrium with the air temperature T in the concave chamber, is first offset to 0 μV, and then when a reverse current is passed, it is cooled by the Pertier effect and the humidity is increased. When the energization is stopped after water droplets have formed on the contacts,
The fluctuation of the negative thermocouple electromotive force V of this wet contact shows a flat signal that first rises sharply due to the stoppage of energization, then slowly rises in temperature due to the vaporization of condensed water, and then the inflow of heat from the reference contact. The restoration curve that rises to the initial offset voltage of 0 μV is shown. Of this restoration curve, the turning point electromotive force Vd at which the flat signal that slowly rises due to the vaporization of the condensed water is the dew point temperature. In the program software for a personal computer that can read the turning point electromotive force Vd on the curve and automatically reads the turning point electromotive force Vd indicating the dew point temperature in this measuring instrument.
The fluctuation of the negative thermoelectric countermotive force V of the wet contact after the cooling energization is stopped is changed every minute time Δt seconds to V ₁ , V ₂ , V ₃ , V ₄ , ... Vn, Vn _{+ 1} , Vn _{+ 2,} when ... and digitally recorded, the time difference [delta] V / delta] t of the thermoelectric TaiOkoshi power V of each delta] t seconds is defined as ΔVn = Vn-Vn _+1, the second floor time difference for each delta] t seconds delta ² when defining the V / delta] t ² and _{ΔΔVn = ΔVn-ΔVn +1, 1} ) the varying KyokutenOkoshi power Vd at the time of proper cooling is the first to be ^{Δ 2 V / Δt 2 ≧ 0} V value, 2) Since the turning point electromotive force Vd at the time of overcooling is a rebound V value at which ΔV / Δt ≧ 0 first,
As a whole, the program software for the automatic reading personal computer, which sets the V value at the earlier time of both or the V value at the same time of both as the inflection point electromotive force Vd,
From the automatically read inflection point electromotive force Vd of the wet contact, the temperature T of the dry contact that is constantly measured, and the 25 ° C. calibration curve obtained in advance, the final object of the measurement sample is non-destructive and calculates display 25 ° C. water potential value (osmotic value) [psi ₂₅ directly, continuously, Peruchiia type thermocouple psychrometer for automatically measuring. In the temperature compensation method to enable on-site measurement with drastic temperature fluctuations
Because unique calibration for each sensor is the 25 ° C. calibration curve, later in terms of the varying KyokutenOkoshi power Vd at temperature T to 25 ° C. HenkyokutenOkoshi power V _25, 25 ° C. calibration curve [psi ₂₅ = the water potential values are substituted into f _{(V 25} ²⁾ While obtaining the (osmotic value) [psi _25,
The daily change of the inflection point electromotive force Vd is correlated by the quadratic regression equation of the temperature T, and if T = 25 ° C. is substituted into the quadratic regression equation, the 25 ° C. inflection point electromotive force V ₂₅ can be obtained. Further, the daily change of the ratio Vd / V ₂₅ of the inflection point electromotive force Vd and the 25 ° C. inflection point electromotive force V ₂₅ depends on the temperature T, and the unique temperature correction formula for each sensor is Vd / V ₂₅ =. Since it is correlated with f (T ² ),
The 25 ° C. change is substituted by substituting the change point electromotive force Vd at the temperature T into V ₂₅ = Vd / f (T ² ) in which both terms of the unique temperature correction formula obtained for each sensor are replaced. It converted into TenOkoshi power _{V 25,} further by substituting the 25 ° C. calibration curve ^{_{Ψ 25 = f (V 25 2}} ), calculated directly display the last is the object the water potential values of the measurement sample (osmotic value) [psi ₂₅ The Peltier type thermocouple cyclometer according to claim 1, wherein the non-destructive, continuous, and automatic measurement is performed. In a configuration that discloses a method for creating the 25 ° C. calibration curve unique to each sensor,
Since the inflection point electromotive force Vd according to claim 1 is greatly affected by the cooling current and the cooling time, the appropriate cooling current and cooling time unique to each sensor must be set and measured before the start of measurement. ,
The creation of a 25 ° C. calibration curve unique to each sensor is to be tested in a constant temperature room at 25 ° C. or according to the temperature correction of claim 2 for measurements of concentrated solutions with a known osmotic pressure of Ψ25 at ₂₅ ° C. After converting the turning point electromotive force Vd at the temperature T to the 25 ° C. turning point electromotive force V ₂₅ , the 25 ° C. turning point electromotive force V ₂₅ and the known osmotic pressure Ψ ₂₅ are plotted and the sensor is used. nondestructive according to claim 1 or 2, characterized in that is carried out by obtaining second order regression curve of unique _{V 25,} that is [psi ₂₅ = _f a _(V ²⁵ 2) each, continuous, Peruchiia for automatically measuring Type thermocouple cyclometer. The water potential value is the water potential value of a leaf, and the leaf is sandwiched by a clothespin-type leaf attachment, and the thermocouple sensor is inserted from below into an aluminum storage tube attached to the lower surface of the clothespin. And fix it, and measure by bringing the opening of the concave chamber into close contact with the back of the leaf with many stomata.
The claim is characterized in that the water potential value Ψ ₂₅ in terms of 25 ° C. of the leaf is directly calculated and displayed from the inflection point electromotive force Vd of the wet contact, the temperature T of the dry contact, and the 25 ° C. calibration curve. The Peltier type thermocouple cyclometer for non-destructive, continuous, and automatic measurement according to any one of 1 to 3. The water potential value is the water potential value of soil, and an attachment for soil in which a fine stainless wire mesh having a mesh of 40 mesh or more is stretched at the lower end of an aluminum storage pipe having a predetermined length is embedded vertically downward in the soil. The thermocouple sensor is inserted into the aluminum storage pipe from above, the upper end of the aluminum storage pipe is wrapped with vinyl tape to fix the sensor connection cable to make it waterproof, and the opening of the concave chamber is opened to the wire mesh. It is measured by pressing it under the soil through
The claim is characterized in that the water potential value Ψ ₂₅ in terms of 25 ° C. of the soil is directly calculated and displayed from the inflection point electromotive force Vd of the wet contact, the temperature T of the dry contact, and the 25 ° C. calibration curve. The Peltier type thermocouple cyclometer for non-destructive, continuous, and automatic measurement according to any one of 1 to 3.