JPS5830534B2 - Moisture content and basis weight measuring device for sheet-like objects - Google Patents

Description

Detailed Description of the Invention This invention uses a cavity resonator into which microwaves are introduced to determine the moisture content and basis weight of a sheet-like object, such as paper, based on the attenuation of the microwave and the resonant frequency of the cavity resonator. The present invention relates to a device for measuring the moisture content and basis weight of a sheet-like object, which is calculated by measuring the deviation.

In general, water content per unit volume (moisture content) and weight per unit area (basis weight) are used as standards to indicate the quality of paper, for example.

Conventionally, measurements of moisture content and basis weight have been performed using separate measuring instruments.

That is, the former measurement of water content uses microwaves or infrared rays.

For example, it is known that the energy of microwaves is significantly attenuated by moisture, so it is determined by irradiating the paper to be measured with microwaves of a predetermined frequency and measuring the amount of attenuation.

Furthermore, the latter basis weight is measured using β rays.

As described above, no device has been found in the past that can measure moisture content and basis weight using the same device.

Furthermore, since beta rays, which are harmful to the human body, were used to measure basis weight, the protective equipment became large, which caused problems in handling.

Furthermore, when using the above-mentioned apparatus for measurement, it is difficult to perform measurement during the paper manufacturing process (on-line measurement).

The present invention has been made based on the above circumstances, and its purpose is to provide a cavity formed by a pair of metal containers with openings facing each other at a predetermined distance so that an object to be measured can be inserted therein. a body resonator, a means for introducing microwaves into one of the vessels, a means for detecting the microwaves derived from the other vessel, an attenuation amount of the detected microwaves, and an amount of attenuation of the detected microwaves; It is possible to measure the moisture content and basis weight of the object to be measured using a measuring device with a simple configuration, and it is also possible to measure the moisture content and basis weight of a sheet-like object that poses no danger to the human body. The present invention aims to provide a moisture content and basis weight measuring device.

An embodiment of the present invention will be described below with reference to the drawings.

In FIGS. 1 and 2, 11 is a cavity resonator.

This cavity resonator 11 is divided into two parts, for example, an upper container 12 and a lower container 13, and the opening 12. ．． 13. are opposed to each other at a predetermined slit-like interval, and these openings 121, 13. are provided with flanges 122, 132 facing outward, respectively, and these flanges 122, 13□ are capacitively coupled to form the cavity resonator 11.

The slit-like space between the upper container 12 and the lower container 13 serves as an insertion portion 15 into which a sheet-like object to be measured, that is, paper 14 is inserted.

Further, a coupling hole 1 is provided in one side of the upper part of the upper container 12.
23 is provided, and the waveguide 1 is inserted into this coupling hole 123.
6 are provided in communication.

Electromagnetic wave signals from a microwave oscillation tube, for example, a klystron 17, are introduced into the upper container 12 through this waveguide 16.

Further, 18 is a sawtooth wave oscillator that applies a sawtooth voltage to the klystron 17.

On the other hand, a coupling hole 133 is provided in the lower side of the lower container 12, and a waveguide 19 is provided in communication with the coupling hole 133.

The lower container 12 and the detector 20 are electromagnetically communicated via a waveguide 19.

The output of this detector 20 is supplied to the vertical axis input and the horizontal axis input of an oscilloscope 21, respectively, together with the output of the sawtooth wave oscillator 18.

That is, in the apparatus configured as described above, first, when the object to be measured is not inserted into the insertion part 15 of the cavity resonator 11, the dielectric loss in the cavity resonator 11 is approximately "1".
It becomes.

In this state, when a sawtooth voltage is supplied from the sawtooth wave oscillator 18 to the klystron 17, the klystron 17 outputs microwave power that is frequency-modulated according to the input voltage level, and the microwave power is generated within the cavity resonator 17. inserted.

Then, when the oscillation frequency of the klystron 17 approaches the resonant frequency of the cavity resonator 18, a detected output is derived from the detector 20 via the waveguide 19.

This detection output is supplied to the vertical axis input and horizontal axis input of the oscilloscope 21 together with the output of the sawtooth wave oscillator 18, respectively.

Therefore, a resonance curve having a resonance voltage and a resonance frequency specific to the cavity resonator 11 as shown in FIG. 3I is drawn on the off-scilloscope 21.

Next, when paper having moisture and basis weight is inserted into the insertion port 15 of the cavity resonator 11, the cavity resonator 11
As shown in FIG. 3H, in the resonance curve of , the peak voltage level decreases and the resonance frequency increases, for example.

That is, since the energy of microwaves is attenuated by moisture as described above, the resonant voltage is attenuated by the moisture content of the inserted paper.

Further, since the resonant frequency of the cavity resonator 11 differs depending on the dielectric volume within the resonator 11, in this case, the frequency is increased, for example, due to the dielectric volume specific to the inserted paper material.

Furthermore, when a thick paper having a larger basis weight than the above paper is inserted into the cavity resonator 11, the resonant voltage is further attenuated and the resonant frequency is further increased as shown in FIG.

In this way, the relationship between the change in the resonant voltage and the resonant frequency is proportional to the moisture content and basis weight of the paper, which is the inserted sample.

Therefore, the water content of paper is calculated by measuring the deviation of the resonance voltage with and without paper inserted into the cavity resonator 11, and the basis weight of paper is calculated with and without paper inserted into the cavity resonator 11. It can be determined by measuring and calculating the deviation of the resonant frequency in the case where it is not.

As a specific measurement means, the moisture content can be measured by comparing the peak value detection of the output of the wave detector 20, and the basis weight can be measured by using the oscilloscope 21 to measure the sawtooth shape at each peak frequency. It can be determined by measuring and comparing the sweep voltages of the wave oscillator 18.

According to the moisture content and basis weight measuring device described above, the cavity resonator 110 is divided into two parts, an upper container 12 and a lower container 13, with opposing openings 12. ．． 13. An insertion section 15 into which a paper 14 is inserted is provided, and microwaves whose frequency is modulated by a sawtooth wave voltage are introduced into the cavity resonator 11.

By measuring changes in the resonant voltage and resonant frequency when the paper 14 is inserted and not inserted into the insertion portion 15 of the cavity resonator 11, the moisture content and basis weight of the paper 14 can be calculated. .

Therefore, it is extremely effective because the moisture content and basis weight can be measured with a simple configuration.

Furthermore, since the measurement of basis weight does not use beta rays, etc., it has the advantage that there is no danger to the human body.

In the above embodiment, the shape of the cavity resonator 11 was rectangular, but the same effect can be applied even if a circular cavity resonator is used, and if the object to be measured is not only paper but also other dielectric materials in the form of a sheet. Similarly measurable.

Furthermore, the moisture content and basis weight may be measured by sampling the paper, but in this device, the measurement target area of the paper located inside the cavity resonator 11 is the opening of the opposing portions of the upper and lower containers 12 and 13. Since it is specified by area, continuous measurement of moisture content, basis weight, etc. is easy and reliable.

Therefore, it is also possible to install this device in the paper manufacturing process, run the paper 14 inside the insertion section 15, and continuously measure on-line.

However, in the latter case, it is conceivable to record the measurement results on, for example, a pen recorder.

The moisture content and basis weight thus determined provide information necessary for paper quality control, etc.

As detailed above, according to the present invention, it is possible to measure the moisture content and basis weight of the object to be measured with a simple configuration using a cavity resonator, and there is no danger to the human body. , for example, the moisture content of sheet-like objects, which can also measure the profile (width unevenness of paper), which is extremely important for paper quality control.
A basis weight measuring device can be provided.

[Brief explanation of drawings]

The first figure is a schematic configuration diagram showing an embodiment of the water content and basis weight measuring device for a sheet-like object according to the present invention, and the second figure is a perspective view showing an example of a cavity resonator used in the present invention. FIG. 3 is a diagram showing an example of measurement results according to the present invention. 11...Cavity resonator, 15...Insertion section, 17...Klystron, 18...
Sawtooth wave oscillator, 20...Detector, 21...
...Otscilloscope.

Claims (1)

[Claims] 1. A cavity resonator configured by a pair of metal containers each having one side open and the openings facing each other with a small gap therebetween;
means for introducing a microwave signal into one of the metal containers constituting the resonator, means for detecting the microwaves derived from the other container, an attenuation amount of the detected microwaves, and the cavity. means for measuring the resonant frequency of the resonator, and a means for measuring the resonant frequency of the resonator;
A device for measuring moisture content and basis weight of a sheet-like object, characterized in that the sheet-like object to be measured is inserted and the moisture content and basis weight are calculated from the measured attenuation amount and resonance frequency.