JPH0810185B2 - Method and apparatus for predicting moisture content in infrared moisture meter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for measuring a predicted moisture content in an infrared moisture meter.

[0002]

2. Description of the Related Art An infrared moisture meter generally obtains the moisture content from the weight change rate of the sample by heating and drying the sample, and the moisture content M is

[0003]

[Equation 1] Given in. Here, Wo is the initial weight of the sample before heating, and Wt is the weight of the sample when the time t seconds has elapsed.

As a method for determining the water content based on the weight change of the sample when the sample is heated and dried, the water content is obtained from the weight change of the sample when the sample is heated and dried for a predetermined period of time, and the water content change rate. In some cases, the water content is determined by heating and drying until the value becomes less than or equal to a predetermined value, and the water content is determined based on how much the weight at that time changes from the weight before heating and drying.

In the former case, if the drying time is too short, water remains, so that a low water content is calculated, and therefore it is necessary to dry for a longer time than usual. In addition, since the drying rate varies depending on the sample amount of the sample, the water content obtained when sampling and measuring an arbitrary amount varies.

In the latter case, since the heating and drying is continued until the weight change rate becomes equal to or less than the predetermined value, a substantially constant moisture content can be obtained even if the sample amount varies. Since the heat drying must be continued until the drying is completed, there is a problem that the measurement time is long. For example, it takes about 15 to 20 minutes for a paddy having a moisture content of 13 to 32%.

[0007]

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a method and apparatus for measuring a predicted moisture content in an infrared moisture meter that shortens the measurement time of the moisture content of a sample.

[0008]

The method and apparatus for predicting moisture content in an infrared moisture meter according to the present invention comprises: introducing a required amount of a sample into the infrared moisture meter and starting heating and drying the sample at predetermined time intervals. , Weigh the sample, calculate the moisture content at each measurement point and the rate of change of the moisture content from the measured values, and calculate the moisture content in the final state from the calculated multiple moisture content and the rate of change In this way, the predicted moisture content when the difference between the predicted moisture content predicted at every predetermined time and the predicted moisture content obtained before that becomes a certain value or less is determined as the moisture content of the sample. .

[0009]

Principle of the Invention Generally, the drying curve of a sample is

[0010]

[Equation 2] It can be expressed as. here,

Mo is the initial moisture content before the start of drying and is usually zero. M _E is the final moisture content when the moisture is substantially dry. Mt is the water content when t seconds have passed before and after the start of drying. a and b are constants.

The mathematical expression 2 is represented in a graph as shown in FIG. When this formula is transformed,

[0013]

[Number 3] _{Mt = a (Mo-M E} ) exp (at + b)

When this is differentiated with respect to time,

[0015]

[Equation 4]

Therefore,

[0017]

(Equation 5)

In Equation 5, Mt is the moisture content calculated by substituting the weight Wt measured at every predetermined time Δt after starting the heating and drying of the sample into Equation 1, and dMt / dt is Calculate by dividing the difference (Mt-Mt ') between the water content Mt' obtained at the previous measurement point and the water content Mt obtained at this measurement point by a predetermined time Δt. The remaining unknowns are ME and (1 /
a). Therefore, Equation 5 is a linear function (y = ax +
It can be represented in the form of b). Therefore, in the measurement performed at every predetermined time, the moisture content Mt obtained at two consecutive measurement points and the change rate (Mt-Mt ') / Δt calculated at each of those time points are substituted into the above equation 5. Then, a binary simultaneous linear equation can be obtained. The final moisture content M _E is calculated by solving this simultaneous equation. In the present invention, this is referred to as the predicted moisture content.

However, immediately after the start of heating and drying, the rate of heat energy consumed for increasing the temperature of the sample itself and its peripheral members is high, so that the drying curve shown in Equation 2, that is, the straight line shown by the linear function of Equation 5 is used. Since it is located at a position outside of the above range, even if the final moisture content is predicted and calculated at this point, the final moisture content will not be correct. Therefore, after confirming the measurement time point at which it is determined that the required time has elapsed after the start of superheat drying and that the drying curve of FIG. 2 is substantially over, the predicted water content calculated after that time is set as the final water content. Need to be adopted.

In the present invention, the difference between the predicted moisture content calculated at each measurement time point and the predicted moisture content calculated before that, preferably, the difference between the predicted moisture content calculated at the previous measurement time point is calculated, When the difference becomes smaller than a predetermined value, it is determined that it has been confirmed that the drying curve represented by Formula 2 has been obtained, and the predicted moisture content at that time is regarded as the final moisture content.

By the way, if the predicted moisture contents of two adjacent measuring points are simply compared, the difference between them may happen to be extremely small. In such a case, a large error will occur in the predicted moisture contents. Therefore, when a simultaneous equation consisting of N linear functions obtained based on N continuous measurement points at three or more time points is solved, the predicted water content closest to satisfy all the N linear functions is obtained. When the difference between this and the predicted moisture content obtained by linear regression of the rate ME and N times of 2 minutes before is smaller than a predetermined value, the predicted moisture content is determined as the final moisture content. Preferably.

For example, when N = 3, the measurement point t₁,
t₂, T₃Moisture content at the time of Mt₁, Mt ₂, Mt₃When
The rate of change at that time is dMt1 / dt, dMt₂/ D
t, dMt₃If / dt,

[0023]

(Equation 6)

Each of these equations is solved by two simultaneous equations, and the closest predicted moisture content that satisfies all linear functions is obtained by linear regression. That is, the value of M E obtained in the three linear functions shown in Equation 6 is taken as the mean square of the respective errors from the predicted straight line of the linear function, and is set so as to be the minimum. ME is calculated based on the following function.

[0025]

FIG. 3 is a block diagram showing the overall construction of the present invention.

In the figure, the electronic balance 1 detects the load of the sample G acting on the sample dish 2 by the weight detection unit 1 '. The detection signal is taken into the arithmetic control unit 4 via the AD converter 3.

The sample dish 2 is surrounded by a windshield 5 and an infrared lamp 6 for heating and drying the sample is arranged above the sample dish 2. The area around the lamp 6 is surrounded by a lamp cover 7, and the lamp cover 7 and the windshield 5
To form a heating chamber. A temperature detection sensor 8 such as a thermistor is arranged in proximity to the lamp 6, and its output is taken into the arithmetic control unit 4 via an amplifier 9 and an AD converter 10. The lamp 6 is controlled by the heat source control unit 11 which is controlled by the control signal generated based on the temperature signal from the temperature detection sensor 8 in the arithmetic control unit 4.

The arithmetic and control unit 4 is composed of a microcomputer, and stores a CPU 41 for executing a measurement program and various calculations and controlling peripheral devices, a ROM 42 in which a measurement program and the like are written, a weight detection value and various calculation results and the like. RAM 43 having an area for writing, a nonvolatile E ² ROM 44 capable of writing and erasing, an A / D converter 3, 10 and an input port 45 for receiving a signal from an external device such as a timer 12, which are mutually connected. Connected to the bus line. The arithmetic control unit 4 also determines the moisture content,
A display 13 for displaying temperature, time, etc., and a keyboard 14 for giving instructions to the CPU 41 are connected.

Next, the operation of the embodiment of the present invention shown in FIG. 3 will be described with reference to FIG.

In step 50, when a start command is input from the keyboard 14, in step 51 the arithmetic control unit 4 takes in the initial weight value Wo of the sample before the start of heating and drying detected by the weight detection unit 1 ', It is stored in the RAM 43. Then, in step 52, the arithmetic control unit 4 causes the lamp 6
Is activated to start heating and drying, and the timer 12
To start.

Next, at step 53, it is judged whether or not a time that is an integral multiple of the predetermined time Δt has elapsed. This is to realize the function of measuring the weight of the sample every ΔT seconds. If YES is determined here, in step 54, the weight Wt of the sample at that time is measured, and in step 55, the moisture content Mt at that time is calculated according to Formula 1, and stored in the RAM 43. And step 5
In 6, increase from the difference from the moisture content obtained at the previous measurement △
By calculating Mt and dividing this by Δt, the rate of change in water content (ΔMt / Δt) is calculated and stored in the RAM 43.

At step 57, it is judged whether or not ΔT × 3 seconds or more has elapsed since the timer 12 was started.
Since this example shows an example of calculating the predicted moisture content using the measurement results at three measurement points, it is for confirming that the measurement of at least the first three points has been completed. . If NO is determined here, the start 53
Then, the procedure similar to the above is repeated. YE here
If it is determined to be S, in step 58, the predicted moisture content M is calculated by linear regression calculation based on the moisture content Mt calculated for the last three measurement points and its change rate (ΔMt / Δt).
Calculate _E.

In step 59, it is determined whether or not ΔT × 4 seconds has elapsed since the timer 12 was started.
This is because the calculation of the difference in the predicted moisture content in the next step 60 is performed because the second predicted moisture content is not calculated in step 58 unless the first four measurement points have elapsed after the start of the timer 12. Because you can't. If NO in step 59, the process returns to step 53, and the measurement at the next measurement point is performed in the same manner as described above. If YES is determined here, the difference ΔM between the predicted water content obtained this time in step 60 and the predicted water content calculated at the measurement point one time before.
_E is calculated, and in step 61 it is determined whether the difference value ΔM _E is less than a predetermined value 0.1. This value of 0.1 is empirically obtained as a value at which it can be determined that the actually measured drying curve is substantially on the previously predicted drying curve. If NO is determined here, the process returns to step 53 and the measurement is performed again every predetermined time, and steps 54, 55, and 5 are performed.
It is repeated 6, 58, 60 and 61. Step 6
If YES is determined in step 1, the superheat drying operation is canceled in step 62, and the predicted moisture content calculated last in step 58 in step 63 is used as the final moisture content in the display unit 1.
Displayed in 3 and complete all measurements.

As another embodiment, measurement points are set every 10 seconds, the moisture content at five consecutive measurement points is applied to the drying curve formula, and the predicted moisture content M _E is calculated by linear regression.
It is also possible to compare the calculated value before the calculation and calculate the predicted water content with the convergence condition when the difference becomes 0.1 or less.

FIG. 4 and FIG. 5 show the results of 13% using this method.
FIG. 4 is a histogram showing the results when measuring 151 points of paddy having a moisture content of 32% from FIG. 4, and FIG. Is O. 27. It seems that the error is on the negative side because it is a deviation from the dry curve formula,
If a correction term is provided in the equation, the error can be reduced. Further, FIG. 5 is a histogram showing the distribution of measurement time.
According to this, the measurement time is distributed from 3 minutes to 13 minutes, and the moisture content is calculated on the average of 8 minutes.

[0036]

EFFECT OF THE INVENTION It is 15
In contrast to the time required from 20 minutes to 20 minutes, the method according to the present invention predicts the drying curve while heat drying is in progress, and when the prediction reaches a substantially steady state, the final moisture content is determined. The measurement can be finished before the final dry state is reached. Therefore, the water content can be measured in less than half the time of the conventional method, and the measurement efficiency can be significantly improved.

[0037]

[Brief description of drawings]

FIG. 1 is a flowchart showing an execution procedure of a predicted moisture content measurement according to an embodiment of the present invention.

FIG. 2 is a diagram showing a drying curve for explaining the principle of the present invention.

FIG. 3 is a block diagram showing an embodiment of the overall configuration of the present invention.

FIG. 4 is a histogram showing a distribution of errors in the measured values of the predicted water content when 151 samples were measured using the apparatus according to the present invention.

FIG. 5 is similar to FIG. 4, but with the device according to the invention
It is a histogram which shows the distribution of the measurement time when measuring one sample.

[Explanation of symbols]

 1 Electronic Balance 2 Sample Dish 4 Calculation Control Unit 6 Infrared Lamp

Claims (2)

[Claims] 1. A step of introducing a required amount of sample into an infrared moisture meter, a starting step of measuring an initial weight of the introduced sample, starting heating and drying of the sample, and starting a timer, While measuring the weight of the sample at time intervals, a measurement calculation step of calculating the moisture content based on the measured value and the initial weight measured in the starting step, and the moisture content of each measurement calculation step A change rate calculation step of calculating a change rate, a plurality of change rates calculated in the measurement calculation step and a plurality of change rates calculated in the change rate calculation step are used to calculate the change rate of the sample. And the difference between the predicted water content obtained in the prediction step and the predicted water content obtained in the previous step is less than or equal to a predetermined value,
And a step of determining the final predicted moisture content as the moisture content of the sample. 2. A sample dish for receiving the introduced sample, a measuring means for measuring the weight of the sample, an infrared heating means for heating and drying the sample, and a predetermined time after starting the drying by the infrared heating means. A means for calculating the moisture content by measuring the weight of the sample by the measuring means for each, a means for calculating the change rate of the moisture content based on the moisture content calculated by the moisture content calculating means, and the moisture content calculation A plurality of water contents calculated by the means, a means for predicting the water content of the sample based on the plurality of change ratios calculated by the change ratio calculation means, and a predicted water content predicted by the prediction means. A predictive moisture measuring device in an infrared moisture meter, comprising means for determining the moisture content as a moisture content of the sample when the difference from the previously determined moisture content is equal to or less than a predetermined value.