JPH01287450A - Water content measuring method using microwave - Google Patents

Abstract

PURPOSE:To obtain a high-reliability value by conveying a sample in a measurement area continuously while vibrating the sample, and detecting the weight of the sample passing through the measurement area and the attenuation quantity of microwave energy by the sample plural times and calculating the water content. CONSTITUTION:When a vibrator 17 is vibrated, a trough 14 is vibrated repeatedly and slantingly to above as shown by an arrow (u) according to the elasticity and inclination of a slanting leaf spring 16 and the sample which is supplied from a supply port 19 to this trough 14 is conveyed continuously while swung upward. Simultaneously with the conveyance of the sample, a microwave is sent to the measurement area from a transmitting horn 1 and then received by a receiving horn 2 so that the microwave passes through the sample on the trough 14 and the trough 14. The energy of the microwave that the receiving horn 2 receives is microwave energy after attenuation and transmitted to a detection processor. Further, the weight of the sample from a load cell 5 provided to a rack 15 is transmitted to the detection processor. The detection processor calculated the water content from the attenuation quantity and weight which are already known to obtain the high-reliability measured value.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for measuring moisture content using absorption of microwaves by moisture.

BACKGROUND OF THE INVENTION There are many methods and devices for measuring moisture content that utilize absorption of microwaves by moisture. In many cases, the 1Ee received by the emitted microwave from moisture present in the propagation path to the receiver is detected and measured. Among these, those that detect the amount of attenuation of microwave energy due to moisture in the sample,
Examples of 2.3 regarding the relationship between the sample and microwaves are JP-A-55-132938 (leak type);
JP-A No. 56-92435 (transmission type), JP-A No. 59-Sho.
-87346 (reflective type), etc.

These devices have means and mechanisms to compensate for errors in detected values due to the weight of the sample, the temperature at the time of detection, or the reflection of microwaves from surrounding equipment. The principle is that there are always evenly distributed samples.

However, in measurement devices using a single microphone wave applied to industrial equipment, the sample is not always evenly distributed in the measurement area due to the sample itself or the way the sample is supplied, Uneven distribution of samples is occurring. For example, in a mechanism in which a thimble sample is automatically supplied from an industrial equipment main body to a measurement area using a small belt, the above-mentioned uneven distribution occurs due to unevenness in the amount of sample taken out or uneven supply position. And this uneven distribution is
Coupled with the fact that the potential of microwaves in the air propagation path is usually high in the center of the measurement area, this causes large fluctuations in the detected value, which is the basis for calculating the moisture content, and is one of the causes of errors in the measurement results. It is the cause.

Figure 4 (a) shows the experimental results showing the voltage on the receiving side detected by placing the microwave absorber d at various positions in the middle of the microwave propagation path (in the air). It represents the situation.

In this experiment, as shown in the same figure (b), an acrylic resin flat plate C was placed across the microwave propagation path between the transmitting horn a and the receiving horn 25, which were arranged facing each other with a gap between them. , the upper surface of the measurement area is divided into C1 to C9 as shown in the same figure (c), and the same absorber d is placed in one of the divisions (respectively, and the The detected voltage at the receiving horn b is shown in correspondence with the position where the absorber d is placed.

The above-mentioned absorbent body d is a commercially available absorbent sheet (ECCO8ORB, trade name, Brace Japan Co., Ltd.) having urethane foam A-me as a basic component, which is cut into a rectangular shape. Also, the frequency used for microwave is 9.45Gl-
1z, acrylic resin plate thickness 9.9mm<1/2・λ/
[Ding...λ: Microphone 1 in vacuum] Wave wavelength, ε dielectric constant of acrylic resin plate, μ: magnetic permeability) half-wave plate,
Detection voltage (reference voltage) when the absorber d is not placed
was 4°80v. Furthermore, the numerical value is the average value of the detection results of three times, and the value in parentheses is the difference from the above-mentioned reference voltage.

In this way, even within the same measurement range, the detected values differ depending on the position of the absorber d (uneven distribution of the sample).

In addition, when the sample is a highly watery powder that easily aggregates, a granular material lacking in fluidity, or an aggregate of irregularly shaped pieces (wood chips, tobacco leaves, tea confectionery, etc.), the uneven distribution in the thickness direction is severe, and bumps may occur. There is a risk of detecting a part and obtaining a protruding measurement value.Furthermore, such samples tend to be unevenly distributed not only in the thickness direction but also in the plane, and especially in the upper part of the belt. In many cases, the problem cannot be resolved by simply scraping or pressing the top surface of the sample with a scraper or roller placed on the surface. Therefore, if this is continuously supplied to the measurement area as it is, the amplitude at the center where the microwave potential is high will change over time, so it is necessary to operate various correction means each time a measurement is made.

Generally, the output from a moisture content measuring device in industrial equipment is linked to the operation of the industrial equipment itself, and if a value that fluctuates with an error every measurement is detected as in the conventional method, it will have a large effect on the equipment itself. , and you can't get the product you want.

Problems to be Solved by the Invention It is an object of the present invention to provide a measurement method that can eliminate uneven distribution of a sample and alleviate the influence of prominent detected values on measurement results.

Means for Solving the Problems The basic method is to place a sample in the middle of the microwave propagation path, detect the amount of attenuation of microwave energy by the sample, and measure the water content of the sample.

Continuously transport the sample supplied to the measurement area while vibrating it.

Both the weight of the sample passing through the measurement area and the amount of attenuation caused by the sample are detected multiple times.

From the detected value obtained, the water content is estimated based on the known attenuation/weight/moisture content correlation formula.

The process of continuously transporting the working sample through the measurement area while vibrating it is as follows:
Eliminate uneven distribution of the sample supplied to the measurement area in the thickness direction and in the plane.

The process of detecting both the weight of the sample passing through the measuring zone and the microwave attenuation l by the sample multiple times provides data for accurately calculating the water content of the raw material.

Embodiment FIG. 1 is a block diagram showing an example of a measuring device for carrying out the present invention.

In the figure, a transmitting horn 1 (transmitting antenna) and a receiving horn 2 (receiving antenna) are vertically disposed facing each other with an interval therebetween, and the interval is used as a microwave propagation path 3.

A vibrating conveyor device 4 is arranged in the propagation path 3 and forms a transport path for the sample, and this device is equipped with an O-docel 5 .

9. The base of the transmitting horn 1 mainly includes a Gunn diode.
Microwave oscillator 6 that generates 45 GHz microwaves
is connected.

The power supply circuit 7 is a conventional one, which obtains two DC power supplies of 15V and 9V from an AC power supply of 100V or 200V, and supplies the microphone to the one-wave oscillator 6.

The receiving horn 2 includes a microwave receiver 8. Receiving circuit 10.
A detected value processing device 11 is connected, and a driver 13 for driving a display device 12 and industrial equipment in accordance with measured values is connected to the detected value processing device 11.

The microwave receiver 8 is mainly composed of a detection diode, and the reception circuit 10 logarithmically converts and amplifies the voltage value sent from the microwave receiver 8 to a value that can be easily processed later. uses what is called a personal computer.

The receiving circuit 9 amplifies the voltage value sent from the load cell 5 and sends it to the detected value processing device all.

As shown in FIGS. 2 and 3, the vibrating conveyor device 4 has a structure in which a trough (1) 14 is supported on a pedestal 15 via inclined plate springs 16 provided at the front and rear sides on both left and right sides, and a pie break 17 is connected. There is. The trough 14 is integrally molded from polypropylene material (plate thickness: 1 mm), and a hole is provided at a location corresponding to the measurement area, and a foamed polystyrene plate (foaming ratio: 1o) is attached to the hole. The material of the trough 14 may be any synthetic resin, such as acrylic resin, which is hard and has low absorption and reflection of microwaves. The pedestal 15 is the third
As shown in the figure, the load cell 5 is placed in a frame body in which a portion corresponding to the microwave propagation path 3 is cut out.

The load cell 5 is for measuring Mm of the sample 18 passing through the trough 14, and its detected value is connected to the detected value processing device 11 via the receiving circuit 9. Reference numeral 19 is a supply port for the sample 18.

When the vibrator 17 is driven, the trough 14 is repeatedly vibrated diagonally upward in the direction of arrow U due to the elasticity and inclination direction of the inclined plate spring 16, and the sample supplied to the rough 14 from this i to the supply port 19 is shaken upward. move forward continuously. In this case, the sample 18 supplied from the supply port 19 onto the trough 14 initially has unevenness in thickness or is unevenly distributed in a planar arrangement, but during transportation, the pie break 17
The strong vibration of the glass eliminates these uneven distributions, and the sample becomes uniformly distributed throughout the flow path of the trough 14.

Such homogenization by vibration is particularly suitable for homogenizing aggregates of small pieces, such as tea cakes and wood chips, where each piece exhibits elasticity.

The flow path in the trough 14 is a sample transport path L (FIG. 5), and the range of microwave irradiation with respect to this transport path is 14ts.

Simultaneously with the transport of the sample, a microwave of 9.45 GHz (7) that mainly tosses the TEIO motor is emitted from the transmitting bone 1 to the measurement area S, and is transmitted through the sample on the trough 14 and the receiving horn. 2 received. The microwave energy received by the receiving horn 2 is the microwave energy that has been absorbed by the moisture contained in the sample on the trough 14 on the way or attenuated by reflection and absorption by equipment in the propagation path. The detector 8 converts the detected value into a voltage and transmits it to the detection processing device 11. Note that the amount of attenuation energy due to reflection and absorption by equipment in the propagation path is constant and is small.

Further, the load cell 5 provided on the mount 15 is transmitted to the sample @ injury detection value processing device 11 at each time. Then, the detection processing device 11 extracts and processes the detected value of the received microwave energy and one side of the sample at the required timing.

That is, the sample 18 is flattened by vibration and passes through the measurement tIUS in a uniform distribution, during which ff1fa and the received microwave energy are detected.

In the detected value processing device 11, for example, the processing shown in the flowchart of FIG. 6 is performed.

This chart takes tea confectionery as a sample during the tea manufacturing process, and calculates the received microwave energy of the sample and the sample In each time.
/ taken out every 20 seconds to obtain the detected value M1゜Wl, these are summarized every 60 seconds to obtain the respective values M and W, and from these, the water content G of the sample is determined based on the following formula.
is calculated.

G = 72.17 This is a known correlation between attenuation, ff1fl, and water content obtained through statistical processing.

The detected value processing device a11 clears the registers W and M in step S1 at the beginning of the processing operation, and stores the detected value (voltage mo) with no sample in the trough 14 and the 1-code cell output value (weight wo) in the register m01WO. ) as the reference value, and further set the timer to t=60 (seconds) to initialize it. In step 2, reset and start the timer.

Step s3. Attenuation of sample weight k・(wl-wo) and microwave energy every 1/20 seconds in s4
1 (mo-ml) is added to register W and register M. Note that Wl is the detected value of weight input to register W1, ml is the detected value of received microwave energy input to register m1, and detected value W1 and detected value m1 are taken in at almost the same time. . Also, k
are constants and are the area of the measurement region (S) and the area of the sample flow path (L)
The ratio of k=s/L.

In step S5, it is determined whether 60 seconds have elapsed in the current cycle, and if 60 seconds have not elapsed, the process returns to step S3 and repeats the input between the sample tffl and the attenuation, and accumulates these values for each. After 60 seconds, step S
6, the water content G is calculated, and the result is transmitted to the display device 12 such as a CRT or the driver 13.

In step S7, the accumulated data W and M are cleared, and in step S8, it is determined whether initialization is necessary. If not, the process returns to step S2, the timer is reset and then restarted, and the above process is repeated.

As a result, the calculated moisture content G is output every minute. When initialization is necessary, for example, a part of the sample adheres to and remains on the trough 14, and the detected values (voltage mQ, heavy weight WO) in a state where there is no sample change over time. In this case, the process returns to step S1 every predetermined time period and changes the reference value.

1/2 adopted in the processing using the 70-chart above
The time intervals of 0 seconds and 60 seconds may become longer depending on the capability of the detected value processing device 11, the response capability of industrial equipment, etc. Generally, one moisture content G is determined by multiple detection values W1 and m.
It may be calculated based on the cumulative value of l.

Note that the detection interval between detection value W1 and ml (number of times/hour 1!i1
) do not necessarily have to match, for example, the detected value wl,
The sample moisture content can be calculated from the above correlation formula based on the average value W obtained by dividing the cumulative value of ml by the number of detections and the rain. However, it is better to make the time intervals (60 seconds in this embodiment) for determining W and M the same.

The heavy FAW1 of the sample detected multiple times and the detected value m1 of the received microwave energy can be processed and used in various other ways. For example, W in the above formula
, instead of using the cumulative value between the weight and attenuation as M, use the average value obtained by dividing this cumulative value by the number of detections, or use the cumulative value of the central part of the normal distribution for each of the attenuation gate and sample type a. You can take measures such as

Effects of the invention: The transported sample in the measurement area is not unevenly distributed in the thickness direction or in the plane, the detected values are stable multiple times, and there is no disturbance due to large fluctuations in the detected values, so highly reliable measured values can be obtained. It will be done.

In particular, it is possible to accurately measure the moisture content of aggregates of irregularly shaped pieces such as tea confectionery and book chips, which has been difficult in the past.

[Brief Description of the Drawings] Fig. 1 is a block diagram of an embodiment of the device, Fig. 2 is a partial front view, Fig. 3 is a partial side view, and Fig. 4 (A) (
B) (C) are diagrams shown for explanation, FIG. 5 is a plan view, and FIG. 6 is a flowchart in one embodiment. DESCRIPTION OF SYMBOLS 1... Transmission horn, 2... Receiving horn, 3... Propagation path, 4... Vibration conveyor device, 5... Load cell, 6... Microwave oscillator, 7... Power supply circuit, 8
...Microwave receiver, 9...Load cell receiving circuit, 10...Microwave receiving circuit, 11...Detected value processing device, 12...Display device, 13...Driver,
14... Trough, 15... Frame, 16... Inclined plate spring, 17... Vibrator, 18... Sample, 19
...Sample supply port. (2 others) Figure 1 Figure 2 Figure 4 Exit

Claims (1)

[Claims] This is a method for measuring the moisture content of a sample by placing a sample in the middle of the microwave propagation path and detecting the amount of attenuation of microwave energy by the sample, in which the sample is continuously transported through the measurement area while vibrating. , and is characterized in that both the weight of the sample passing through the measurement area and the amount of attenuation due to the sample are detected multiple times, and the moisture content is calculated from the detected values based on a known attenuation amount/weight/moisture content correlation formula. Moisture content measurement method using microwave.