JP2667021B2 - Method and apparatus for measuring moisture in infrared moisture meter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and an apparatus for measuring moisture in an infrared moisture meter.

<Conventional technology> An infrared heating moisture meter (infrared moisture meter) combines a balance and a heat source to determine a moisture content (M) from a weight change rate due to drying. The moisture content changes every moment as it dries. Here, Wo is the initial weight of the sample, and Wt is the weight of the sample when the time t has elapsed.

The water content of the sample to be obtained is calculated by using the above equation (1) as a value when the time set in the timer has elapsed, and a change in the water content within a specified time (for example, 30 seconds) is below a certain value ( (For example, 0.05%), there is a method of determining that the constant value has been reached and obtaining the value at that time. The latter is called the automatic stop function.

Previously, this type of infrared moisture analyzer has a certain weight (for example,
5g or 50g) samples were taken for measurement, but recent moisture analyzers measure at any weight. In this case, the drying speed varies depending on the weight of the sample, and the lower the weight, the faster the time to reach the constant weight.When setting the drying time with a timer, set the drying time longer based on the larger weight. The drying time is usually set to about 20 minutes, depending on the type of sample and the moisture content.

Also, when measuring using the automatic stop function,
The drying time differs depending on the sample and the water content.

<Problem to be Solved by the Invention> An object of the present invention is to provide a moisture measuring method and apparatus in an infrared moisture meter capable of measuring the moisture content of a sample having an arbitrary weight in a short time.

<Means for Solving the Problems> According to the method and apparatus for measuring moisture in an infrared moisture meter according to the present invention, a required amount of a sample is introduced into the infrared moisture meter, the weight of the sample is measured, and the introduced sample is measured by an infrared ray. When heating and drying are started at the same time, a timer is started, and when the timer measures a first predetermined time after entering the reduced-rate drying stage, the weight of the sample is measured to calculate the moisture content, and the timer is operated. When the second predetermined time, which is longer than the first predetermined time, is measured, the weight of the sample is measured to calculate the water content, and the second predetermined time elapses based on the water content at the first and second predetermined times. It is configured to calculate the amount of change in the remaining moisture content after that and add the amount of change in the remaining moisture content to the moisture content after the elapse of the second predetermined time to obtain the initial moisture content of the sample. .

<Function and Effect of the Invention> A small amount of a sample is sampled from a large amount of the object to be measured, and the sample is placed on a sample dish of an infrared moisture meter. Next, the sample is irradiated with infrared rays to start heating and drying the sample and start a timer. The timer is the first and second
The water content of each sample is measured when the predetermined time is measured, the difference between the two measured values is obtained, and based on this difference, the amount of change in the remaining water content after the second predetermined time is calculated, and the amount of change is calculated. Is added to the moisture content after the lapse of the second predetermined time to obtain the initial moisture content of the sample.

Therefore, the weight of the sample to be sampled does not need to be weighed, it is only necessary to introduce an arbitrary amount into the infrared moisture meter, and heating and drying with infrared light until most of the moisture in the sample has evaporated. When most of the water in the sample has evaporated, heating and drying are stopped, and the remaining change in the remaining moisture content is calculated and added to the moisture content at the final measurement. Since the moisture content of the initial sample is calculated, the measurement time is greatly reduced, and more real-time feedback can be provided to the moisture management line.

<Examples> FIG. 2 is a diagram showing how the moisture content calculated by the equation (1) changes with drying, in the case where the weight of the sample having the same moisture is changed (W ₁ > W ₂ > W ₃ ). FIG. A immediately after the start of drying
In the area, the lower the weight, the easier the moisture to fly, and the specified time Δ
Moisture change within t is large (ΔM3>ΔM2> ΔM1), there is no fixed relation in the next B area, and the weight is small in the next C area, which is the declining drying stage where most of the water has evaporated. Is a proportional relation (ΔM3
>ΔM2> ΔM1).

On the other hand, FIG. 3 shows a case in which samples having different moisture contents are measured with the same weight. Moisture change ΔM during Δt
As can be understood from FIG. 2, when the weight is changed with the same water content, the relationship between the water content and the change in water content up to the final water content is inversely proportional in the A range and proportional in the C range. In addition, when the moisture is changed with the same weight, the proportion is proportional over the entire area as can be understood from FIG. Since the measurement by the infrared moisture meter is arbitrary in both moisture and weight, based on the moisture content change ΔM between Δt obtained when most of the moisture has evaporated,
In order to obtain the water content change Mr from the time until the water content change almost disappears, it is necessary to use the C region where ΔM and Mr are in a proportional relationship, and to complete the measurement in as short a time as possible. , C around the beginning of the region. For example, Δt is 4.5 minutes and 5.0
If the time is set to about 30 seconds, the water content can be measured in 5 minutes. The water content at 4.5 minutes and 5 minutes after the start of the measurement is M4.5, M5, and the change rate of the water content thereafter is expressed by a linear expression of M5−M4.5. (2) (c and d are constants determined by the sample) The final moisture content M is obtained by adding Mr to M5, and M = M5 + Mr = M5 + (M5-M4.5) c + d (3) Since c and d are strictly affected by the moisture value, c is a
It is better to set M5 + c and d to bM5 + d. Therefore, the equation (3) is as follows: M = M5 + Mr = M5 + (M5-M4.5) (aM5 + c) + (bM5 + d) = M5 + a (M5-M4.5) M4.5) + d (4) Therefore, the residual moisture (Mr) is (M5-M4.5) M5, M5,
It is a function of (M5-M4.5).

Here, X = (M5−M4.5) M5, Y = M5, Z = M5−M4.5
Then, M = M5 + aX + bY + cZ + d (5) In order to determine the values of a, b, c, and d, it is necessary to measure (N ≧ 4) times the actual water content, and the combination of the water content at 4.5 minutes, the water content at 5 minutes, and the final water content is obtained.

Here, the constants a, b, c and d take different values depending on the type of the sample. In the case of corn grits (corn powder), a = 0.006, b = −0.262, c = 6.86, d = −0.16 Is used.

FIG. 4 is a graph showing the degree of coincidence between the water content obtained by the automatic stop function and the calculated water content according to the above formula (4) when corn grits are used as a sample, and the straight lines are the same. Line. In this case, a standard deviation σ = 0.092% is obtained.

In the case of a sample having a high water content of about 40% or more, the effect of shortening the time is not so significant because the area A in FIG.

FIG. 1 is a block diagram showing one embodiment of the present invention.

The electronic balance 1 detects a load acting on the sample dish 2, and outputs the detected value as an electric signal from the weight detection unit 1 '. The output is taken into the arithmetic and control unit 4 via the AD converter 3.

The sample dish 2 is surrounded by a windshield 5,
Above this, an infrared lamp 6 for heating and drying the sample is provided. The lamp 6 is surrounded by a lamp cover 7, and the lamp cover 7 and the windshield 5 form a heating chamber. A temperature sensor 8 such as a thermistor is disposed near the lamp 6, and its output is input to a temperature detector 9 and output as an electric signal proportional to the temperature. The output of the temperature detector 9 is taken into the arithmetic control unit 4 via the A / D converter 10, fed back to the heat source control unit 11 that supplies a current to the lamp 6, and used for controlling the heating temperature by the lamp 6. You.

The arithmetic control unit 4 is composed of a microcomputer, and executes a measurement program and various calculations and controls each peripheral device. A CPU 41, a ROM 42 in which a relation between a heating temperature and a weighing error of the electronic balance 1 and a measurement program are written, It has a RAM 43 with an area for storing various calculation results, weight detection values, temperature detection values, etc., a nonvolatile E ² ROM 44 that can be written and erased, and an input port 45 for inputting signals from external devices. Are connected to each other by a bus line. The input port 45 has the above-mentioned AD converters 3 and 10
In addition to the output, the output of the timer 12 that measures the time from the start of heating to the completion of drying is input. The arithmetic control unit 4 includes:
Further, a display 13 for displaying the moisture content calculated by a command from the CPU 41 and a keyboard 14 for giving an instruction to the CPU 41 are connected.

When the user sets the coefficients a, b, c, and d of the original sample, the data is written into the E ² ROM by inputting from the key switch. If the microprocessor is provided with a coefficient determining program of the formula (4), the user can determine the coefficient using an actual sample and automatically write the coefficient into the E ² ROM.

The moisture measurement of the sample is performed according to the flow shown in FIG. In step 51, the measurement temperature of the sample chamber is set, the sample is inserted into the sample dish 2, and the initial weight of the sample is measured. When the timer 12 is started in step 52 and it is confirmed that 4.5 minutes have elapsed in step 53, the weight of the sample is measured and the moisture content M4.5 is calculated in step 54. Further, the elapse of 5 minutes is confirmed in step 55, the weight of the sample is measured again in step 56, and the water content M5 is calculated. Then step
At 57, the initial moisture content of the sample is calculated in accordance with the equation (4) and displayed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIGS. 2 and 3 are diagrams for explaining the principle of the present invention, and FIG. 4 is a diagram for carrying out the present invention to measure water content of a sample. Data diagram showing the degree of agreement between the results obtained and the measurement results obtained by the conventional method,
FIG. 5 is a flowchart showing an execution procedure of the present invention. (Explanation of symbols) 1: Electronic balance, 2: Sample dish, 4: Operation control unit, 6: Infrared lamp, 8: Temperature sensor, G: Sample.

Claims (4)

(57) [Claims] 1. A step of introducing a required amount of a sample into an infrared moisture meter and measuring the weight of the sample; heating the introduced sample with infrared rays to start drying and starting a timer; A step of measuring a weight of the sample to calculate a moisture content when measuring a first predetermined time after entering the rate-decreasing drying step; and a second step in which the timer is longer than the first predetermined time. Calculating a moisture content by measuring the weight of the sample when a predetermined amount of time is measured, and the residual moisture content after the second predetermined time has elapsed based on the moisture content in the first and second predetermined times. And a step of calculating the initial moisture content of the sample by adding the remaining moisture content variation to the moisture content after the elapse of the second predetermined time. Moisture measurement method 2. The method according to claim 1, wherein the second predetermined time is a time approximately 30 seconds after the first predetermined time has elapsed. 3. The method according to claim 1, wherein the calculating step calculates the amount of change in the remaining moisture content according to the following equation. ｛A (M5−M4.5) + b｝ M5 + c (M5−M4.5) + d where a, b, c and d are constants, M4.5 is the moisture content after the first predetermined time has elapsed, M5 is the moisture percentage when the second predetermined time has elapsed. 4. A sample dish for receiving an introduced sample, an infrared heating means for heating and drying the introduced sample, a drying operation before starting heating by the infrared heating means, and a reduction rate by starting a drying operation by the infrared heating means. Means for measuring the weight of the introduced sample when a first predetermined time has elapsed after entering the drying step and when a second predetermined time which is longer than the first predetermined time has elapsed; And a means for calculating the water content of the introduced sample after the second predetermined time has elapsed, and the remaining water content after the second predetermined time has elapsed based on the water content after the first and second predetermined times. And the amount of change in
A moisture measuring device in an infrared moisture meter, comprising: means for adding the amount of change in the remaining moisture content to the moisture content after the elapse of the second predetermined time to obtain the initial moisture content of the introduced sample.