JPH03137551A - Detecting method of moisture - Google Patents

Abstract

PURPOSE:To conduct accurate and quick measurement by a method wherein a plurality of standard samples are measured, working curves thereof are stored, the working curve approximated by an output of 0% moisture of a culture ground support to be detected is selected and this working curve is modified by an output of 100% moisture. CONSTITUTION:Standard samples of a plurality of culture ground supports are measured beforehand by a specific heat type moisture detector and working curves showing the relationship between an output and a maximum specific yield percent are determined and stored. These curves are expressed by a cubic polynominal. First, a sample of culture ground support to be measured is dried at a temperature of 110 deg.C for 24 hours or under direct rays of the sun and then put in a prescribed case, and measurement thereof at 0% moisture is conducted. Based on the data thus obtained, the working curve of the standard sample approximated by an output of 0% moisture is selected. Next, a state of 100% moisture, i.e. a maximum specific yield 100%, is prepared and measurement is executed again. The value of a constant in the cubic polynominal of the selected standard sample is modified, and modification is conducted so that an actual measured value of a moisture meter at the maximum specific yield 100% may become 100%.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a moisture detection method for detecting the moisture content of a culture medium support such as soil, sand, or rock wool using a specific heat type moisture detector. Regarding improvements.

(Prior art) For example, in a culture device using a medium support made of soil, sand, rock wool, etc. alone or in combination, the water content of the medium support has a great influence on the growth of cultured plants. control is extremely important.

In order to control the amount of moisture, it is necessary to accurately detect it.
A specific heat type moisture detector described in Japanese Patent No. 644 is known.

In this specific heat type moisture detector, the moisture sensor part has a metal part and a plastic part in a long and narrow container with one end closed, and a heater and a temperature measuring part placed at a certain distance from the heater. The sensor is fixed to a metal part, and another temperature sensor of the same configuration for comparison is provided at a position where it can block the influence of heat from the heater. Here, the temperature sensor is composed of a platinum thin film resistor, a thermal lightning pair, or the like. Further, the other end of the container is provided with a lead-out portion for lead wires of a heater and a temperature sensor.

To measure the amount of water using the above-mentioned specific heat type moisture detector, when the moisture sensor part is inserted into the culture medium support and the heater is activated, the heat of the heater is transmitted to the temperature sensor as a temperature measuring part. At this time, part of the heat is absorbed by the medium support and escapes. This endothermic amount (escape amount) increases as the moisture content of the culture medium support increases. If the amount of heat absorbed by the culture medium support is large, the heat transferred to the temperature measurement part will be greatly reduced, and conversely, if the amount of heat absorbed by the culture medium support is small, the heat transferred to the thermometer 1TP1 will not decrease much. Therefore, if the amount of heat generated by the heater is kept constant, for example, if a calibration curve showing the relationship between the amount of water in the culture medium support and the amount of temperature rise is determined in advance, the temperature rise at the temperature sensor can be determined. By measuring the amount (amount of temperature change), the amount of water in the medium support can be determined.

(Problems to be Solved by the Invention) As mentioned above, the conventional method of detecting moisture content using a specific heat type moisture detector uses a previously prepared calibration curve and a regression equation such as a cubic equation to The moisture content was calculated by calculating the output value and displaying the moisture content, or by simply amplifying the output value (voltage value) of the sensor as is or by amplifying it based on a calibration curve prepared in advance.

Therefore, in either case, the water content cannot be determined unless a calibration curve is prepared in advance, and it is necessary to spend about a month or so on preparing this calibration curve.

Furthermore, since the calibration curves of specific heat type moisture detectors differ depending on the type and particle size of the culture medium support, it was necessary to create calibration curves for each individual.

The present invention was made in order to eliminate the above-mentioned disadvantages, and an object of the present invention is to provide a moisture content detection method that can easily detect moisture content without creating a calibration curve for each culture medium support to be detected. shall be.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention detects the moisture content of a single or mixed medium support such as soil, sand, or rock wool as an output of a specific heat type moisture detector. In this moisture detection method, standard samples of a plurality of culture medium supports are measured in advance to obtain a plurality of calibration curves showing the relationship between output and maximum capacity %, and the moisture content of the culture medium support to be detected is 0. %, select an approximate calibration curve based on the output when the water volume is 100%
It is characterized in that the calibration curve is corrected based on the output of the medium support to be detected in %.

To explain using the flowchart in FIG. 1, first, a sample of the culture medium support to be measured is dried at 110° C. for 24 hours or by direct sunlight, placed in a predetermined case, and the moisture content of 0% is measured. An approximate calibration curve (details will be described later) is selected based on this data. Next, the water content is 10
Create a state of 0%, that is, 100% of the maximum water capacity, measure again, and correct the error. This means that a calibration curve that is very close to the sample has been created, and in actual measurements, it is possible to display the water content as a percentage of the maximum water capacity, that is, as a percentage of the maximum water capacity.

(Function) The accuracy is extremely high because a calibration curve with a moisture content of 0% is almost the same, and even with a maximum water capacity of 100%, the error has been corrected. Furthermore, by preparing calibration curves in advance for standard samples of various culture medium supports, the maximum water capacity % can be quickly obtained.

(Example) The details of the present invention will be explained below by way of an example with reference to the drawings.

Figure 2 shows the specific heat type moisture detector 1 used in this example.The measuring case 2 consists of a cylindrical body with a bottom plate 2a at one end, and the bottom plate 2a has holes of 2 to 3 dragon diameters. 2b are provided in large numbers. In addition, a filter paper is placed inside, and the structure is such that the culture medium support 5a such as soil or sand contained therein does not fall.

The specific heat type moisture sensor 3 (hereinafter referred to as moisture sensor) can be similar to the one described in the conventional example, but the one in this example has a pencil-shaped shape, and its head A thermocouple is installed inside a two-hole ceramic pipe, and a heater is installed on the outside of the pipe, and is insert-molded with water-resistant resin. . Moisture meter 4
is a device that has a CPU and controls each part based on the data from the moisture sensor 3 and other manually inputted data, and also performs arithmetic processing to display, for example, the maximum water volume percentage of the sample. To explain the operation using the block diagram of FIG. 3, first, a constant n1 start signal is input from the external input circuit 11 into the CPU 12, and the start delay timer 13
operates for about 5 seconds, during which time the base voltage of the moisture sensor 3 before the heater voltage is applied is input from the amplifier circuit 14 to the A/D conversion circuit 15, and the initial hold circuit 16 is input in the CPU 12.
is memorized. The start delay timer 13 expires, the heat-up timer 17 operates, and the heater power supply circuit 1
A current of about 250 to 400 mA is passed from the sensor 8 to the moisture sensor 3. The heat-up timer 17 expires after about 60 seconds, but just before that, the voltage of the moisture sensor 3 is stored again by the sampling timer 19 from the A/D conversion circuit 15 to the sampling hold circuit 20 in the CPU 12. Next, the arithmetic circuit 21 subtracts the initial hold value and the sampling value to obtain the sensor output voltage (X). In addition, 10 types of calibration curves (6 types of soil, 3 types of sand,
One type of rock wool) is built-in, and the control circuit 22
The measured output (x) value is substituted into the cubic equation in the calibration curve selected by the keyboard 23 connected to the keyboard 23, and the moisture content is calculated.

The water content in this case is the maximum capacity water content %. This calculated value is displayed on the LCD unit 24. Also, L
The value displayed on the CD unit 24 can be determined by inputting either the maximum water capacity % or the sensor output voltage (x) on the keyboard 23.
can be selected by operating.

The above-mentioned calibration curve is based on the i
It was derived based on the lJ determination results, and can be used to measure various culture medium supports with different particle sizes and materials.

In addition, the calibration curve can support up to cubic equations, y-axA3+
Each coefficient aSb, c of bxA2+cx+d.

d can be changed using the keyboard 23, but in reality d
By changing the value of , it is possible to adjust to a known moisture content.

Next, a case will be described in which commercially available river sand is measured using the specific heat type moisture detector 1 described above.

Take the river sand 5a in measurement case 2 and heat it to 110℃.
Dry thoroughly for 24 hours. After 24 hours have elapsed, the temperature of the river sand has fallen to room temperature, and then the moisture sensor 3 is inserted, and after selecting the sensor output voltage (x) display on the moisture meter 4 with the keyboard 23, measurement is performed.

Table 1 shows the measurement results. The output was measured three times and the average output was 0.968v. In other words, the output when the water content (maximum water capacity %) is 0% is o, 968v.

Table 1 Then, a calibration curve is selected based on this value, and this is done using the selection standard table in Table 2. This includes the type of medium support (soil, sand, rock wool) and the calibration curve number.
(0 to 9) and the water content 0, which is the standard for selecting each calibration curve.
% range of the output voltage of the moisture sensor 3 is described.

Table 2: The specifications of each calibration curve are briefly explained according to their No.

0 Granular soil with a particle size of 3 mm or more 1 Granular soil with a particle size of 1 to 3 mm 2 Fine granular soil with a particle size of 0.5 to 1 mm 3 Particle size 0.
Fine-grained soil of 5 mm or less 4 Mixed soil of clay and fine-grained soil 5 Clay 6 Sea or river sand with a grain size of 1 mm or more 7 Sea or river sand with a grain size of 1 mm or less 8 Sea or river sand with irregular grain sizes 9 Artificial medium ( rock wool).

Now, the calibration curve No. 7 is selected as the approximate calibration curve from the selection specification table in Table 2, and the calibration curve No. 7 is entered manually using the keyboard 23.

A calibration curve for the sample (for example, river sand) can be derived from the output voltage (x) during drying.

In addition, when the slope of each calibration curve 30 is shown in the semilogarithmic graph of FIG. 4, up to about 70% can be expressed as a straight line.
The slopes are also very similar, and the output during drying is slightly different.

Next, measure the output at 100% of the maximum water capacity of this river sand and correct the approximate calibration curve No. 7 to obtain a corrected calibration curve,
As a result, the moisture jil (maximum water capacity %) is calculated and detected by the moisture meter in a timely manner, but the above-mentioned correction method and the displayed value % of the moisture meter 4 will be explained in detail.

First, after sufficiently drying the river sand 5a, the measuring case 2
The sample was placed in a container, water was supplied from the bottom for about 24 hours, it was taken out, and the water molecule fi (maximum water capacity 100%) was measured after being left for 24 hours, and the maximum capacity % was calculated by weight while gradually drying. This is to compare with the maximum water capacity percentage displayed by the moisture meter 4.

In addition, in order to improve the accuracy of the moisture meter 4, the maximum water capacity 1
The actual measured value of Moisture Meter 4 is 97°2%, and the cubic equation of calibration curve No. 7 (Y
--104,999xA3+442.299xA2-6
d-312,70 of 57.998x+312.706)
By adding 2.8 to 6 to set d=-315,506, the moisture meter 4 calculated the maximum water content % using a corrected calibration curve, and then air-dried the sample.

FIG. 5 is a graph in which the vertical axis represents the maximum water capacity (%) of the moisture meter 4, and the horizontal axis represents the maximum water capacity (%) determined from the weight. A solid line 31 with a black circle indicates the corrected calibration curve, and a broken line 32 with a white circle indicates the calibration curve No.7.

As is clear from this graph, the error between the value actually determined by the drying method and the value displayed by the moisture meter 4 using the corrected calibration curve is within ±3%, and there is no problem in actual use. It is. In addition, the display error of the moisture meter 4 when using the uncorrected calibration curve No. 7 is within the range of ±6%,
The accuracy is sufficient for simple use.

The entire moisture detection method described above will be explained with reference to the flowchart shown in FIG. 6 and the block diagram shown in FIG. 3.

When the power is turned on, the voltage value manually input to the A/D conversion circuit 15 of the moisture meter is read (step 1), and the voltage value and 130
mV (step 2), and if the voltage value is smaller, a display means is selected (step 3). When the voltage display is selected, the display is switched to the voltage display (step 4), and when the water content display (maximum water capacity % display) is selected, the display is switched to the water content (step 5). is input (step 6). Next, a command to start measurement is issued (step 7). Therefore, the voltage application to the heater is delayed for 5 seconds (step 8), during which time the base voltage of the temperature detection sensor is A/D converted and stored (
Step 9). After the delay time passes, the heater turns on (Step 10), and current flows for 60 seconds (Step 11).
Immediately before the current is cut off, the voltage of the temperature detection sensor is A/D converted and stored (step 12). Heater is off
Then (step 13), the stored voltage is subtracted to calculate the output voltage (x) (step 14). The display method for the calculated value is selected (step 15), and
If the voltage is displayed, it will be displayed as is (step 16),
In the case of displaying the water content, calculation is performed based on the calibration curve, and the water content is displayed as the water content (maximum human capacity water Ω%) (step 17). In response to this display, the moisture content is adjusted (step 18).
.

The above steps are repeated at appropriate times.

In this embodiment, a moisture sensor equipped with a thermocouple is used, but the present invention is not limited to this, and any sensor that detects by the movement of heat may be used. Further, the calibration curve is not limited to that of this example, and may be larger or smaller.

[Effects of the Invention] As detailed above, the present invention selects a calibration curve approximate to the maximum human capacity water mO%, and corrects the calibration curve by outputting at the 100% position, thereby improving detection accuracy. This method has excellent effects, such as being able to perform rapid measurements even on new culture medium supports, since the measurement is extremely high and corrections only need to be made at 100% position.

[Brief explanation of the drawing]

FIG. 1 is a flowchart explaining the detection procedure of the present invention;
Figures 2 (a) and (b) are the same <perspective view and main bottom view of the specific heat type moisture detector used in the example, Figure 3 is a block diagram of the moisture meter of the specific heat type moisture detector, Fourth
The figures are the same (explanatory diagram of the calibration curve used in the example), FIG. 5 is the same (explanatory diagram of the moisture meter display value in the example), and FIG. 6 is the same (the flow chart of the example). 1・・・・・・・・・・・・Specific heat type moisture detector 5
a......Medium support 30...
...... Calibration curve

Claims (1)

[Claims] A moisture detection method that detects the moisture content of a single or mixed medium support such as soil, sand, or rock wool using the output of a specific heat type moisture detector, in which standard samples of multiple medium supports are measured in advance and output. Calculate multiple calibration curves showing the relationship between % and maximum water capacity, select an approximate calibration curve based on the output when the moisture content of the detection medium support is 0%, and then calculate the output at the maximum water capacity of 100%. A moisture detection method characterized by correcting a calibration curve based on the output of a culture medium support.