JPS63120245A - Apparatus for displaying heat conductivity of soil - Google Patents

Abstract

PURPOSE:To display heat conductivity in an extremely efficient manner, by operating and displaying heat conductivity from the measured value through a probe, which has a heater and a temp. sensor mounted in the insulator thereof, on the basis of the known reference measured value from a non-volatile memory. CONSTITUTION:The difference temp. DELTAT of the initial temp. T0 of soil 28 when a current is made to flow to the built-in heater of the probe 27 embedded in the soil 28 and the temp. Tb of the soil when the supply of a current to said heater is stopped is detected by the probe 27 and supplied through an A/D converter 26. Hereupon, interruption is applied to an interval timer 21 and CPU 20 performs the sequence control based on the program of ROM 22. Then, the measured temp. difference DELTATref obtained when the probe 27 stored in non-volatile RAM 23 backed up by a battery is embedded in soil of which the heat conductivity is known is referred to and the heat conductivity lambdab of the soil 28 based on formula I is operated and calculated to be displayed on a display device 30. By this method, the measured result from the same probe is stored in the non-volatile memory only once to display heat conductivity in an extremely efficient manner.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to a soil thermal conductivity display device that measures the thermal conductivity of soil using signals from a probe buried in the soil and displays it on a display device.

(b) Summary of the Invention This invention buries a probe equipped with a heater and a temperature sensor in the soil, detects temperature changes when current is passed through the heater and when the current is stopped, and detects temperature changes based on the detected values. In a device designed to measure the thermal conductivity of soil, the temperature change when a probe is buried in soil with a known thermal conductivity is stored in advance as a reference value, and the reference value and the heat of the known soil are memorized in advance. The thermal conductivity of the soil to be measured is calculated and displayed based on the conductivity and the temperature change when the probe is buried in the soil to be measured.

(C) Foreground of the Invention In farms, there is a growing demand for accurately knowing the amount of moisture in the soil and managing the moisture in the field, leading to effective use of water and increased crop yields. Electrical resistance methods and tensiometer methods are used as general methods for measuring moisture in the field, but these methods have their own advantages and disadvantages, such as the large influence of ions and narrow measurement ranges, making them unsatisfactory.

Therefore, a probe with a heater and a temperature sensor placed inside an insulator is buried in the soil, and the temperature sensor detects the temperature change when heater current is passed through the probe and when the current is stopped. A device has been devised to measure the thermal conductivity of soil based on . This device takes advantage of the fact that the higher the moisture in soil, the higher its thermal conductivity, and measures the temperature increase when current is applied to the heater and the decrease in temperature after the current is stopped. Find the conductivity. By determining this thermal conductivity, the moisture in the soil can be determined.

(d) Purpose of the Invention The purpose of the present invention is to measure soil thermal conductivity using the above-mentioned probe, based on the temperature change when the probe is buried in soil with known thermal conductivity. It is an object of the present invention to provide a soil thermal conductivity display device that can display the thermal conductivity of soil to be measured extremely efficiently by providing a nonvolatile memory for storing the value.

(e) Structure of the Invention This invention is equipped with a probe in which a heater and a temperature sensor are arranged in an insulator, and the probe is buried in soil and the temperature is measured when a current is applied to the heater and when the current is stopped. In a device that detects a change with the temperature sensor and measures the thermal conductivity of soil based on the detected value, the temperature change when a probe is buried in soil whose thermal conductivity is known is used as a reference value. Calculate the thermal conductivity of the soil to be measured based on the nonvolatile memory to store, the temperature change when the probe is buried in the soil to be measured, the reference value stored in the memory, and the known thermal conductivity. The present invention is characterized by comprising a calculation means for calculating the calculated thermal conductivity, and a display means for displaying the thermal conductivity determined by the calculation.

FIG. 1 shows the probe with a portion cut away. The inside of the vibrator 1 is filled with an insulator 2, and a heater 3 and a temperature sensor 4 are arranged in this insulator. When this probe is buried in the soil and a current is passed through the heater 3, if the temperature rise change detected by the temperature sensor 4 is large, it can be determined that the thermal conductivity of the soil is low. On the other hand, if the temperature increase change is small, it can be determined that the soil has a high thermal conductivity. Figure 2 shows the relationship between thermal conductivity and moisture content in soil. As shown in the figure, soil has the property that when it contains a lot of water, its thermal conductivity increases, and when it becomes dry, its thermal conductivity decreases. Therefore,
The moisture content of the soil can be determined by measuring the thermal conductivity.FF1 effect The measurement of the thermal conductivity of the soil to be measured is based on the temperature change when a current is passed through the heater and the temperature when the current is stopped. Do this by referring to the changes. The reason for this is to reduce the influence of soil temperature changes during measurement. In addition, in order to measure the thermal conductivity of the actual soil to be measured, the temperature change in the soil whose thermal conductivity is known is measured in advance as a reference value, and this reference value is combined with the detected value in the soil to be measured. Perform comparison operations. As a result of the comparison calculation, if the temperature change of the measured soil is the same as the temperature change of the reference soil, the thermal conductivity of the measured soil is the same value as the reference thermal conductivity. Additionally, if the temperature change in the measured soil differs from the temperature change in the reference soil, the thermal conductivity of the measured soil will differ by the cumulative ratio of the reference thermal conductivity. It turns out. In the present invention, the temperature change when the probe is buried in soil whose thermal conductivity is known is stored in advance in a nonvolatile memory as a reference value, and the temperature change when the probe is buried in the soil to be measured is stored in the memory. The thermal conductivity of the soil to be measured is calculated based on the stored reference value and the known thermal conductivity, and the thermal conductivity determined by the calculation is displayed.

The third position represents the temperature change when the probe is buried in soil with known thermal conductivity. In addition, in the same figure (81 represents the temperature change when the probe is buried in the soil to be measured.

Figure 3 (C) shows a graph obtained by combining the graphs of Figure 3 (At, CB+) and erasing time. In the same figure, λ1: known thermal conductivity λb: unknown (measured soil ) Thermal conductivity T0: Initial temperature 'I''m + To' is the temperature after heating of the known and unknown soil.In other words, the thermal conductivity λ of the soil to be measured is determined by calculating the equation (1). I can do it.

To find the thermal conductivity λ in equation (1), calculate ΔTr and f/ΔT of the straight line portions of the curves shown in Figure 3 (C1) when the temperature rises and when the temperature falls. Next, proceed as follows. After obtaining the respective values when the temperature rises and when the temperature falls, these two values are further averaged.This averaged value is determined as the thermal conductivity λ1 of the soil to be measured. Therefore, the temperature change when the probe is buried in the soil to be measured (shown in Figure 3 (Bl)) and the temperature change in Figure 3 (shown in Al) stored in the non-volatile memory are stored as is. Compare and calculate the average value of ΔT4./ΔT from the graph shown in Figure 3 (C), and multiply the average value by the known thermal conductivity λ1 to determine the thermal conductivity λ of the soil to be measured. It turns out.

(g1 Effect of the Invention According to this invention, since the temperature change of soil whose thermal conductivity is known is stored in the non-volatile memory, even if the power of the device is turned off and then turned on again, it will not turn off completely (without any problem). Measurement can be continued.Therefore, by storing the temperature change of soil with known thermal conductivity as the reference value only once in non-volatile memory2, the reference value will be used again as long as the reference soil does not change. There is an advantage that there is no need to calculate the 4 degree change between the reference soil and the soil to be measured at the same time, so there is an advantage that only one probe is required; It is possible to ignore the characteristics and changes in characteristics of the probe itself.

(h) Embodiment FIG. 4 shows a partially cutaway external view of a probe used in a soil thermal conductivity display device according to an embodiment of the present invention.

The probe body 10 is made of ceramic glass and is housed in a sealed stainless steel pipe 14. The probe body 10 is provided with four symmetrical holes 10a. The probe is composed of this probe body IO and a terminal block 11 provided at the end thereof, and this probe body IO is embedded in the soil.

Heaters 12a are installed in two of the four holes 10a of the probe body 10 that are facing each other.

12b is inserted, and temperature sensors 13a and 13b made of platinum wire are inserted into the other two opposing holes. Also, two heaters 12a and 12b are installed at the front end of the probe.
and two temperature sensors 13a, 13b are connected.

The terminal block 11 is provided with a terminal bin lla, and this terminal bin lla is connected to a control section (not shown). Note that heater 1
The four holes 10a into which the temperature sensors 2a, 12b and the temperature sensors 13a, 13b are inserted are each filled with alumina. By doing this, the heaters 12a, 12
b and the temperature sensors 13a, 13b can be reliably fixed. Furthermore, the space between the stainless steel pipe 14 and the probe body 10 is filled with alumina. The probe with the above configuration has sufficient strength because the heater and temperature sensor are inserted into the hole in the probe body 10 made of ceramic glass, and the position of the hole is specified, so the heater and temperature sensor are inserted into the hole. There is no possibility that the relative position will shift. This has the advantage of stable characteristics. Further, since the probe body 10 is inserted into a stainless steel pipe, waterproofness is maintained, and furthermore, there is an advantage that insertion into the stainless steel pipe is easy.

FIG. 5 is a block diagram of the control section.

The CPU 20 includes an interval timer 21 for performing timer interrupts, etc., and a ROM that stores programs.
22. A RAM 23 and a RAM 1024 are connected to which measurement data and the like are temporarily stored and a work area for calculations is assigned, and which are backed up by a battery. In this example, a battery-backed RA
M23 constitutes a nonvolatile memory.

From the above 11024, the heater is turned on to the heater relay 25.
A signal is output, and the data of the temperature change detected by the temperature sensor is taken in from the A/D converter 26. soil 2
A heater current is supplied from the heater relay 25 to the heater inside the probe 27 buried in the probe 8, and the temperature change detected by the temperature sensor is sent to the differential amplifier 3.
1. l1024 further includes input oyster-29,
A display 30 is connected. Irukaki-29 is written (
1) Display device 3 for inputting λ1 etc. of the equation
0 indicates (1) λ of 2 or the moisture content σ, which will be described later.

FIGS. 6(4) to 6(C) are flowchart 1 showing the operation of the soil thermal conductivity display device of this embodiment.

The sixth part is a flowchart showing an operation for storing a temperature change when a probe is buried in soil with a known thermal conductivity as a reference value in the RAM 23.

First, in step nu (hereinafter step ni will simply be referred to as ni), the heater is turned on. At this time, heater relay 2
At 1in2, when current starts to be supplied to the heater of the probe 27 from 5, the sample counter i is updated, and n
3, the temperature is measured by the temperature sensor inside the probe. Subsequently, in n4, the measured temperature at that time is stored in a predetermined area of the RAM 23. Next, wait 3 seconds at n5. The above operation is repeated 50 times and sample data every 3 seconds is stored in the memory.

Similarly, in n7 to n12, when the heater is turned off, 50 points of detection data by the temperature sensor every 3 seconds are sampled and stored in the memory.

By completing the above operations, sample standard data T, , 1 to 50 points at the time of temperature rise are stored in the RAM 23.
Trer50 and sample standard data T- when temperature drops
= r 51 to T-t 100 are respectively stored.

FIG. 6+B) shows the operation of storing the temperature change in the RAM 23 when the probe is buried in the soil to be measured.

This operation is completely similar to the operation shown in the sixth device.

That is, n20 to n25 correspond to n1 to n6, and n26
~n31 corresponds to n7~n12. By this operation, the sample measurement data T1 to T50 when the temperature rises and the sample measurement data T51 to T100 when the temperature falls are stored in the RAM 23, respectively.

Fig. 6 (C1 shows the operation of calculating the thermal conductivity of the soil to be measured based on the data stored in the RAM 23 and displaying the thermal conductivity obtained by the calculation. In addition to conductivity, moisture content can also be calculated and displayed.

First, in step n40, ΔTr function f /ΔT is calculated from sample reference data and sample measurement data at the time of temperature rise.
seek. Subsequently, in n41, ΔT-t/ΔT is determined from the sample reference data and the sample measurement data when the temperature decreases. Next, proceed to n42 and rh40. The two values obtained in n41 are averaged, and the average value is multiplied by the known thermal conductivity λ1 of the soil from which the reference value was obtained. Note that λ is input in advance to a predetermined area of the RAM 23 from the input key 29.

is memorized. This determines the thermal conductivity λ of the soil to be measured. Next, in n43, the moisture content σ5 of the soil to be measured is determined. This moisture content σ5 is determined by the following formula.

σb, σ, *λb/λ, (2) Note that σ is the reference soil moisture content, and this value is also input in advance from the input key 29 and stored in a predetermined area of the RAM 23. ing. Next, in step n44, the setting position of a display switch (not shown) is determined.

When the display switch is set to the thermal conductivity display position, the calculated thermal conductivity λ is displayed on the display 30 (n45). Also, if it is set to the moisture content position, the calculated moisture content σ1 is displayed (n46).
.

As described above, in the soil thermal conductivity display device of this embodiment, the RAM is pre-assembled using the temperature change when the probe is buried in soil whose thermal conductivity is known as the reference value.
23, then the same probe is used to detect the temperature change of the soil to be measured, and the thermal conductivity of the soil to be measured is calculated and displayed. There is no need to separate the probe used for the soil and the probe used for the soil to be measured, and furthermore, once the reference value is stored in the memory, there is no need to store it again, making it extremely easy to operate. Become.

[Brief explanation of the drawing]

Fig. 1 shows a schematic configuration diagram of a probe used in the soil thermal conductivity display device according to the present invention, Fig. 2 shows the relationship between soil moisture content and thermal conductivity, and Fig. 3 (A1- (C)
FIG. 2 is a diagram illustrating a method for determining soil thermal conductivity. In addition, Fig. 4 shows a probe used in a soil thermal conductivity display device which is an embodiment of the present invention, Fig. 5 is a block diagram of the control section, and Fig. 6 (C and 'r indicate its operation). It is a flowchart. 1-Probe main body, 3-Heater, 4-Temperature sensor.

Claims (1)

[Claims] (1) Equipped with a probe in which a heater and a temperature sensor are placed in an insulator, and the temperature sensor detects temperature changes when the probe is buried in soil and current is applied to the heater, and when the current is stopped. and a device configured to measure the thermal conductivity of soil based on the detected value, comprising: a non-volatile memory that stores the temperature change when the probe is buried in soil with known thermal conductivity as a reference value; a calculation means for calculating the thermal conductivity of the soil to be measured based on the temperature change when the probe is buried in the soil to be measured, the reference value stored in the memory and the known thermal conductivity; 1. A soil thermal conductivity display device comprising: display means for displaying the determined thermal conductivity.