JPS60173447A - Method for measuring moisture content - Google Patents

Abstract

PURPOSE:To enable measurement of the attenuating rate of a mu wave by packing granular solid in a sample box to a uniform thickness, placing the sample box between two sets of mu wave oscillators and receivers and making the spacing between one transmitter and receiver larger by a specified distance than the spacing between the other transmitter and receiver. CONSTITUTION:A sample is packed into a square sample box 4 and the 2nd electromagnetic horn 5 for signal transmission is disposed below the sample box 4 placed between the 1st electromagnetic horns 2 and 3 for transmission and reception installed at a specified spacing D1. The 2nd electromagnetic horn 6 for reception is disposed above the box 4 and the spacing between the horns 5 and 6 is made D2 by shifting the spacing D2 between the horn 5 and the horn 6 by the distance (d) corresponding to 1/4 wavelength of the microwave used, i.e., 1/2 wavelength of the standing wave from the spacing D1 between the horn 2 and the horn 3. A phase deviation is offset and error is eliminated if the detected voltages of the horns 3, 6 are added. The moisture content of nonuniform granular solid is thus measured and the variance in the measured value is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for measuring the water content of sand-like solids having non-uniform particle sizes using microwaves.

BACKGROUND TECHNOLOGY In general, as a method for measuring the water content of a sand granular solid having a non-uniform particle size, there is a method of drying the object to be measured and calculating the water content from the change in weight before and after drying.

However, this method has the disadvantage that it takes a long time to dry, so it takes a long time to obtain the result of the water content.Also, if the drying temperature is increased to shorten the time, even the volatile substances of the object to be measured will evaporate. This has the disadvantage that the true moisture content cannot be obtained.

On the other hand, as a method for measuring the water content in a short time, there is a method that uses microwaves, high frequency waves, infrared rays, etc., and takes advantage of the fact that these produce electrical changes depending on the water content. (For example, see JP-A-54-153097.) However, when these methods are used to measure the water content in sand-like substances with non-uniform particle sizes, the measured values vary widely, and the water content The conventional wisdom was that it couldn't be done.

Purpose of the present invention The present invention has been made in order to eliminate the above-mentioned drawbacks, and its purpose is to be able to measure the moisture content of granular solids with non-uniform particle sizes in a short time using microwaves. It is an object of the present invention to provide a method for measuring water content that can reduce variations in measured values.

Structure of the Invention In order to achieve the above object, the present invention fills a sample box with granular solids of non-uniform particle size, makes the thickness uniform, and smoothes both the front and back surfaces, and provides first and second tubes that emit microwaves. The sample box is placed between the transmitting electromagnetic bone and the first and second receiving electromagnetic horns that receive the same microwave, and the distance between the one transmitting electromagnetic horn and the receiving electromagnetic horn is set to the other. If the transmitting electromagnetic horn is a certain distance from the receiving electromagnetic horn, it is a quarter of the wavelength of the microwave being used. A configuration is adopted in which the attenuation of microwaves is calculated using

EXAMPLE Hereinafter, an example embodying the present invention will be described with reference to FIGS. 1 to 7.

Here, we use microwaves to measure the moisture content m of the -C substance ■q! state. When microwaves propagate through materials, they are attenuated by absorption inherent in the materials, but absorption by water is particularly large. Therefore, the attenuation of microwaves is largely influenced by the water content contained in or fixed to the substance, and by measuring this attenuation, the amount of water contained in the substance can be determined.

Absorption specific to a substance is dielectric absorption and is determined by the dielectric constant εS of the following equation.

εS−εs'−j(εS″′1σ/εOω)...(1
) However, εS': Dielectric polarization εs L'/: Rotation delay of dipole σ/εOω: Leakage current [εO: Dielectric constant of vacuum.

ω=·2πf, σ-conductivity] As a result, the microwave propagation width (voltage) Eout is expressed by the following equation.

Eout = "in exp [-a14 +j (ω
t-βri1...(2) →-1 εS''; εS+σ/εOω β: Sample thickness λ: Wavelength V; Time As is clear from equation (2) above, the attenuation of microwaves is caused by the dielectric constant εS, It can be seen that G
You will know what you need to do if you press the button.

Furthermore, although it is not expressed in the above equation (2), the attenuation of microwaves is influenced by scattering (reflection, second diffraction, and refraction). In other words, when the surface of sample 1:l (object to be measured) 1 is disturbed as shown in Figure 1, microwaves are reflected and scattered on its upper surface, and if this surface condition changes, the situation of reflection and scattering will naturally occur. The amount of microwaves transmitted varies as well. Therefore, even though the samples have the same thickness, the measured value of the moisture content of the straw due to the attenuation of the microwaves differs due to differences in the surface condition, resulting in variations.

On the other hand, if the surface of J: sea urchin sample 1 shown in Figure 2 is covered smoothly by pressing it with a roller or flat plate, the amount of counter-scattering of microwaves will be a constant amount, and there will be no variation in the measured values. There was found. In other words, when measuring the water content, it is extremely important to keep the FJ of sample 1 constant and to smooth the surface to reduce the variation in measured values. I discovered that.

Further, as shown in FIG. 3, there is an electromagnetic bone 2 for transmitting consisting of a horn main body 2a, a waveguide 2b and a transmitter 2C, and an electromagnetic horn 3 for receiving consisting of a horn main body 3a1, a waveguide 31) and a receiver 3C. When the distance between the receiving electromagnetic horn 3 changes and the distance between the
) changes as shown in Figure 4. This is because the incident wave and the reflected wave of the microwave to be used overlap to produce a standing wave, and this standing wave has a frequency twice that of the incident wave (the microwave to be used). Set the distance between electromagnetic horns 2 and 3 to 4th.
As shown in the figure, if the constant value 1 is set to 1, the microwave voltage F will be a constant value E1 because it will be the value at the location corresponding to the horn spacing D1, but the sample 1 will be placed between the electromagnetic horns 2 and 3. The standing wave causes a phase shift depending on the water content. That is, as shown in FIG. 5(a), the microwave voltage E that is to be measured when the distance between the electromagnetic horns 2.3 is maintained at a constant value D1 and there is no trial between the two bones is a constant value E1.
However, if a test tube is placed between the electromagnetic horns 2 and 3, the standing waves will be out of phase as shown in Figure 5(b).

It is clear that the electromagnetic horn 3 on the receiving side detects a voltage F' different from the microwave voltage E1 as soon as it is measured, causing an error in the measured value. This voltage F' is expressed by the following equation.

E'=E1-a...(3) Therefore, as a result of considering a method of correcting the error in the measured voltage due to the phase shift mentioned above, we filled the sample 1 into the square-shaped sample box 4 shown in FIG. As shown in FIG. 7, a second transmitting electromagnetic horn 5 is placed below the sample box 4 placed between the Ml transmitting and receiving electromagnetic horns 2.3 installed at a constant interval D1. At the same time, a second
The receiving electromagnetic horn 6 is arranged, and the distance D1 between the first transmitting electromagnetic horn 2 and the receiving electromagnetic horn 3 is set to 1'')2 between the second transmitting electromagnetic horn 5 and the receiving electromagnetic horn 6. The horn is shifted by a distance Nd corresponding to a quarter wavelength of the microwave, that is, a half wavelength of the standing wave.
The distance between the two receiving electromagnetic horns 3 is set to D2.
．． It has been found that by adding up the detection voltages of 6, the phase shift can be canceled out and the error can be eliminated. That is, on the second electromagnetic horns 5 and 6 side, as shown in FIG. ) can be added to find the microwave/voltage E1 to be measured.

Note that the present invention can also be embodied in the following Examples.

(1) As a method of shifting the distance d between the transmitting electromagnetic horn 5 and the receiving electromagnetic horn 6, for example, as shown in FIG. 8, changing the length of the waveguide 61) connected to the horn main body 6a Even if you do this, the same effect will be obtained by 1q.

(2) When filling the test sample 1 into the test tube box 4 as shown in FIG. ”It is desirable to do so.

(3) In the case of the sample box 8 having the shape shown in Fig. 10, when the sample is inserted through the opening, the thickness becomes constant due to the sample box, and the sample is pushed against the inner surface of the sample box. Its surface becomes smooth.In the case of this sample box 8, electromagnetic horns 2, 3.5-16 are arranged as shown in FIG.

Effects of the Invention As mentioned in detail below, the present invention has the effect of being able to reduce the moisture content ω of granular solids with non-uniform particle sizes, to be able to determine 1111 at 0 hour, and to reduce the variation in measured values. There is.

[Brief explanation of the drawing]

Figures 1 and 2 are front views showing the surface condition of the sample;
The figure is a side view of the electric rJ & horn, Figure 4 is a graph showing the relationship between the distance between the electromagnetic horns and the microwave voltage, and Figure 5 (a
) to (C) are graphs each showing microwave voltage,
Fig. 6 is a perspective view of the sample box, Fig. 7 is a side view showing the arrangement of the electromagnetic horn, Fig. 8 is a side view showing another example of how to adjust the bone spacing, and Fig. 9 is a side view showing the arrangement of the electromagnetic horn. A perspective view illustrating a sampling filling method, FIG. 10 is a perspective view showing another example of a sampling box,
FIG. 11 is a side view showing the positional relationship between the sample box and the electromagnetic horn shown in FIG. 10. 1...Testing, 2.5...Electromagnetic horn for transmitting, 3.6
...Receiving electromagnetic horn, 4.8...Sample box, Fl.
...Microwave voltage. Special Akira'1 Applicant: Japan? i! Jko Co., Ltd. Agent Patent Attorney On 1) Hiromane Figure 1 LILlllJll Figure 3 Figure 5 "°"-'"".

Claims (1)

[Claims] 1. First and second transmitting electromagnetic horns that transmit microwaves by filling a sample box with granular solids of non-uniform particle size to make the thickness uniform and smoothing both the front and back surfaces. The sample box is placed between the first and second receiving electromagnetic horns that receive the same microwave, and the distance between the one transmitting electromagnetic horn and the receiving electromagnetic horn is adjusted to the desired transmitting electromagnetic horn. and the receiving electromagnetic horn by a certain distance, that is, a quarter wavelength of the microwave to be used, and calculate the amount of microwave attenuation by adding the received outputs of both receiving electromagnetic horns. Characteristic method for measuring water content. 2. The method for measuring water content according to claim 1, wherein a transmitting electromagnetic horn is disposed below the square-shaped sample box, and a receiving electromagnetic horn is disposed above the square-shaped sample box. 3. The method for measuring water content according to claim 1, wherein the sample box is formed into a thin rectangular parallelepiped with a uniform thickness, and the sample is pressed against the inner surface of the sample box to smooth the surface.