JPH0777506A - Moisture measuring equipment - Google Patents

Abstract

PURPOSE:To realize highly accurate noncontact continuous measurement of the moisture content in a sample by applying a high frequency voltage, while sweeping, onto the sample and using the correlation between the frequency for maximizing the induced voltage and the content of moisture. CONSTITUTION:When a high frequency generating section 1 applies a high frequency voltage to a sample while sweeping, the capacitance of a detection coil at a detecting section 2 varies depending on the content of moisture in the sample placed in a container and a resonance phenomenon takes place at a specific frequency. The voltage induced at the time of resonance is delivered to a measuring section 3 through a detection circuit. The measuring section 3 detects the peak value V(f1) of induced voltage at the time of first sweeping and sets a reference value of a comparator equal to the peak value minus DELTAV(f1). Sweep frequencies f2, f3 for the reference value are measured at the time of second sweeping and a resonance frequency f0=(f2+f3) is determined. The moisture content of sample is then calculated according to predetermined working curves between the resonance frequency and the moisture content based on the resonance frequency f0 thus determined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for measuring water content in a sample. More specifically, it relates to an apparatus for measuring moisture without contacting a sample.

[0002]

2. Description of the Related Art Moisture in a sample has been widely measured, and general methods include a drying method, a Karl Fischer method and an infrared absorption method. The drying method is a method in which a sample is dried by heating and the water content is measured from the weight change at that time. The Karl Fischer method is a method for measuring water content by utilizing the fact that a Karl Fischer reagent containing iodine, sulfur dioxide and pyridine specifically reacts with water in the presence of methanol. Further, the infrared absorption method is a method of measuring water content by utilizing that water molecules absorb infrared rays in a specific wavelength range.

[0003]

However, in the moisture measurement by the dry method, low boiling point compounds other than water are also measured as moisture, and in the moisture measurement by the Karl Fischer method, a reagent is necessary, Further, since the Karl Fischer reagent directly contacts the electrode, there has been a problem that the sample and the reagent chemically react with each other to deteriorate the sample. Also, in moisture measurement by infrared absorption method,
Use expensive precision optics, measure absorption at a specific wavelength, and thus be affected by absorption of other components.For example, if air bubbles are included in the sample, the measurement results will be affected and reproducibility is insufficient. However, in continuous measurement, the window surfaces for light transmission and light reception are contaminated in the reaction system, which is a problem in long-term use.

[0004]

Means for Solving the Problems The inventors of the present invention have made earnest studies to obtain a moisture measuring device capable of measuring moisture in a sample by overcoming such difficulties, and as a result, the frequency was swept onto the sample. While the voltage is applied, the relationship between the frequency and water that maximizes the induced voltage detected at a position that is separated from the applied position for a predetermined period, or the relationship between the maximum value of the induced voltage and water, or the integrated value of the induced voltage at each frequency The inventors have found that the above-mentioned problems can be solved by using a water content measuring device configured to detect the water content of a sample based on the relationship between the water content and the water content, and arrived at the present invention.

An object of the present invention is to provide a moisture measuring device which enables highly accurate and highly reproducible moisture measurement. Another object of the present invention is to provide a moisture measuring device that is easy to operate. Another object of the present invention is to provide a moisture measuring device in which the sample and the measuring terminal are not in contact with each other without damaging the sample by the measurement and which enables continuous measurement of the sample.

Therefore, the object of the present invention is to provide an insulating non-magnetic container for containing a sample, an excitation electrode arranged around the insulating non-magnetic container, and a predetermined distance from the excitation electrode. A detection unit containing a detection coil wound around the insulating non-magnetic container, a high-frequency generation unit that applies a high frequency to the excitation electrode while sweeping the frequency, and the detection coil electrically This is easily achieved by a moisture measuring device, which is connected to the measuring unit for measuring moisture in the sample.

The present invention will be described in detail below. The moisture measuring device of the present invention is configured such that an insulating non-magnetic container in which a sample is circulated, an excitation electrode arranged around the non-magnetic container, and the insulating non-magnetic substance at a predetermined distance from the excitation electrode. A detection unit containing a detection coil wound around the container; a high-frequency generation unit for applying a high frequency to the excitation electrode while sweeping the frequency; a detection unit electrically connected to the detection coil and in a sample It is composed of a measuring unit for measuring the water content of. When the sample is directly introduced into the insulating non-magnetic container in which the detection coil is wound, the capacitance of the detection coil changes based on the change in the dielectric constant caused by the difference in water content in the sample. At this time, when a high frequency voltage is applied to the excitation electrode, the detection coil resonates with respect to a specific frequency, and the induced voltage in the detection coil becomes maximum. Therefore, one of the group consisting of the frequency at which resonance occurs, the maximum value of the induced voltage, and the integrated value of the induced voltage at each frequency is measured, and the relationship between the frequency and water at which the induced voltage is the maximum and the maximum value of the induced voltage are measured. Relationship between value and moisture,
Alternatively, the water content is measured by the relationship between the integrated value of the induced voltage and the water content at each frequency.

In the moisture measuring apparatus of the present invention, moisture represents the water content contained in solid, liquid and gaseous substances. The water adhered to the surface of the substance or the adsorbed water adsorbed to the substance, It may be water of hydration or the like that is chemically bound to the substance. In the water content measuring apparatus of the present invention, the detection unit has at least an insulating non-magnetic container for containing the sample, an excitation electrode arranged around the insulating non-magnetic container, and a predetermined interval from the excitation electrode. And a detection coil arranged so as to wind around the insulating non-magnetic container.

In the moisture measuring apparatus of the present invention, the insulating non-magnetic container contains the sample, but the sample may be circulated in the container or filled in the container. The shape of the insulating non-magnetic container in the moisture measuring apparatus of the present invention is not particularly limited, but it is generally cylindrical or polygonal, and preferably cylindrical. Also,
One end of the container may be closed, but when it is open, the sample can be circulated, which is particularly suitable for continuous measurement of the sample in a process or the like.

In the moisture measuring apparatus of the present invention, the material of the container is not particularly limited as long as it is insulative and non-magnetic, but, for example, quartz, borate glass, alumina, silicon carbide or plastic is appropriately selected and used. You can In the moisture measuring apparatus of the present invention, the excitation electrode is arranged around the insulating nonmagnetic container. The electrode may have a ring shape or a flat plate shape.

In the moisture measuring apparatus of the present invention, the detecting coil is composed of a single-phase coil having a large capacitance, since the change in dielectric constant due to the difference in moisture in the sample is detected as the change in capacitance. And Therefore, if the circumference of the container is not wound at least several times, it may be difficult to accurately capture water in the sample as a change in capacitance.

Further, it is preferable that the detection section of the present invention is provided with a detection circuit. The detection circuit selects and takes out a necessary signal waveform from the transmission signal from the detection coil, but is generally electrically connected between the detection coil and the measurement unit. In the moisture measuring apparatus of the present invention, the high frequency generator applies a high frequency to the excitation electrode while sweeping the frequency. The configuration of the high frequency generator is not particularly limited, but in general, an oscillator, a frequency dividing counter, a D-
It is composed of an A converter and a voltage controlled oscillator.

The output of the oscillator is frequency-divided by a frequency division counter, and each timing signal such as a specific oscillation reference step, a specific sweep period and a specific sweep stop gate pulse is sent out. Next, make a specific DC voltage waveform that is output integrated from the transmission reference step signal through the DA converter,
By performing V / F conversion with the voltage controlled oscillator, a high frequency having a specific sweep period and a specific frequency range is created.

The oscillator is not particularly limited, but is preferably a crystal oscillator. The specific transmission reference step is a reference for determining frequency accuracy, and is generally selected from the range of 0.01 to 1 millisecond. The sweep cycle is determined according to the response time (measurement time). The sweep time is not particularly limited, but generally it is 0.
It is selected from the range of 1 to several seconds.

The sweep stop gate pulse is generally selected from the range of 0.001 to 1 millisecond. The specific DC voltage waveform is not particularly limited, but considering that it is a moisture measurement, a ramp waveform of a specific cycle, that is, a horizontal axis as shown in FIG. 1 represents time and a vertical axis represents voltage. It is preferable that the waveform has a sawtooth shape when it is formed.

The specific frequency range is not particularly limited, but is generally several kHz to 100 MHz.
Selected from the range of. In the moisture measuring device of the present invention, the measuring unit is electrically connected to the detection coil, and comprises a resonance frequency at which the induced voltage is maximum, and a maximum value of the induced voltage, or an integrated value of the induced voltage at each frequency. Determine the water content in the sample based on either of the groups.

The measuring unit is not particularly limited, but a peak hold circuit for detecting and storing the peak value of the induced voltage;
A comparator circuit for comparing with a reference value described later; a frequency measuring circuit for measuring the frequency at the time of the induced voltage peak; an I / O for setting / calibrating / displaying / outputting a moisture measuring range
It is generally composed of circuits, and these are CP
It is controlled by a U (Central Processing Unit).

As shown in FIG. 2, when a high frequency wave is applied to the sample while being swept from the high frequency wave generation section 1, the capacitance of the detection coil in the detection section 2 changes depending on the water content in the sample existing in the container, Causes resonance phenomenon with respect to frequency. Then, the induced voltage generated at the time of resonance is sent to the measurement unit 3 through the detection circuit. In addition, signals such as a sweep signal and a sweep stop gate pulse are sent from the high frequency generator 1 to the measuring unit 3.

In the measuring section 3, for example, as shown in FIG. 3A, first, the peak value V (f ₁ ) of the induced voltage induced in the detection coil by the first sweep is calculated as the peak value. The value detected by the threshold circuit and lowered by a predetermined value ΔV (f ₁ ) from the peak value is set as the reference value of the comparator. Next, as shown in FIG. 3 (2), the peak point of the peak value of the induced voltage induced in the detection coil by the second sweep (ΔV,
f ₁ ) is detected by the comparator circuit, and at the same time, the sweep frequencies f ₂ and f ₃ at the same point are measured by the frequency measuring circuit, and the resonance frequency f ₀ (f ₀ = f ₀ =
Calculate (f ₂ + f ₃ ) / 2). Next, using the obtained resonance frequency f ₀ , the water content of the sample is calculated from the resonance frequency created beforehand and the calibration curve of water content.

In addition, in the detection unit 2, not only the relationship between the frequency at which the induced voltage is maximum and the water content, but also the relationship between the maximum value of the induced voltage and the water content, or the relationship between the integrated value of the induced voltage and the water content at each frequency. Can also calculate the water content in the sample. Further, it is preferable that a temperature measuring element is provided near the detection coil. When the temperature measuring element is provided, for example, as shown in FIG.
It is possible to more accurately calculate the water content of the sample from the calibration curve at each temperature of the measurement sample created with the resonance frequency on the vertical axis and the water content on the horizontal axis.

When the sample contains an electrolyte, the maximum value of the induced voltage of the sample becomes low. Therefore, the moisture measuring apparatus of the present invention is further provided with a conductivity measuring element. It is suitable. Generally, when the sample contains an electrolyte, the maximum value of the induced voltage of the sample becomes low. When the conductivity measuring element is provided,
The obtained conductivity is A / D converted and sent to the measuring unit 3, and the measured moisture is multiplied by a correction coefficient corresponding to the obtained conductivity, as illustrated in FIG. It becomes possible to measure the water content more accurately.

The method of measuring the conductivity of the sample is not particularly limited, but for example, a method of measuring the conductivity of the sample using a conductivity cell composed of an inert metal electrode,
Since there is a correlation between the conductivity and the maximum value of the induced voltage, there is a method of obtaining the conductivity from a graph showing the relationship between the maximum value of the induced voltage and the conductivity as shown in FIG.

The correction coefficient corresponding to the conductivity is not particularly limited, but can be calculated as follows, for example. First, with respect to a plurality of solutions containing an electrolyte, the water concentration and the conductivity are respectively measured using both the Karl Fischer titrator and the water content measuring apparatus of the present invention. Next, a calibration curve is prepared with the horizontal axis representing the conductivity and the vertical axis representing (moisture measured using the apparatus of the present invention / moisture measured using the Karl Fischer titrator). Thereby, the correction coefficient for the conductivity of the sample can be obtained.

Next, the obtained water content is transmitted to a display device to display the water content, and an analog output, a serial output, and a control output are sent to each output terminal.

[0025]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Example 1 Using a cylindrical insulating non-magnetic container, the water content was 18.3%.
Using N-methyl-2-pyrrolidone as a standard sample, the water content in the sample was continuously measured using the water content measuring device of the present invention. At that time, a sample temperature measuring element was provided near the detection coil to correct the temperature.

The measurement result was 18.0%, and a highly accurate measurement result was obtained by an easy operation. Example 2 As in Example 1, a cylindrical insulating non-magnetic container was used, and N-methyl-2-pyrrolidone containing a plurality of mutually different concentrations of electrolytes with a water content of 17.2% was standardized. As a sample, the amount of water in the sample was measured using the water content measuring device of the present invention. At that time, the sample temperature measuring element and the conductivity measuring cell were provided in the vicinity of the detection coil, and the correction coefficient was calculated using the temperature correction and the graph shown in FIG. 7 to perform the conductivity correction.

The measurement results are shown in Table 1.

[0028]

[Table 1]

The measurement result is 17.2 ± 0.2%,
Highly accurate measurement results were obtained with easy operation.

[0030]

According to the moisture measuring device of the present invention, not only is it possible to measure moisture with high accuracy and high reproducibility, but also moisture can be measured by an easy operation, and the sample used for measurement is damaged. Therefore, it becomes possible to provide an inexpensive moisture measuring device capable of continuously measuring a sample.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a sawtooth sweep reference signal.

FIG. 2 is a schematic diagram of a moisture measuring device.

FIG. 3 is a schematic diagram showing a method of measuring a resonance frequency (f ₀ ).

FIG. 4 is an example of a calibration curve for obtaining water in a sample.

FIG. 5 is a graph showing the value of the peak voltage with respect to the conductivity of the sample.

FIG. 6 is an example of a graph for obtaining a correction coefficient for the conductivity of a sample.

FIG. 7 is a graph for obtaining a correction coefficient for the conductivity of the sample in Example 2.

[Explanation of symbols]

 1 High frequency generator 2 Detector 3 Measuring unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiro Ichihiro 18-18 Takaido Nishi, Suginami-ku, Tokyo Inside Toko Chemical Research Institute Co., Ltd. (72) Inventor Masumi Nishitani 1-18 Takaido Nishi, Suginami-ku, Tokyo No. 8 Incorporated company Toko Kagaku Kenkyusho (72) Inventor Masanori Hirai 2-5-2 Marunouchi, Chiyoda-ku, Tokyo Sanryo Kasei Co., Ltd. (72) Inventor Hiromasa Kato Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa No. 1000 Sanritsu Kasei Co., Ltd. Research Institute (72) Inventor Ito Japan Man, Chigasaki City, Kanagawa Prefecture 370 Enzo, Mitsubishi Kasei Co., Ltd. Chigasaki Plant

Claims (1)

[Claims] 1. An insulating non-magnetic container for containing a sample, an excitation electrode arranged around the insulating non-magnetic container, and an insulating non-magnetic container at a predetermined distance from the excitation electrode. A detection unit containing a detection coil wound around, a high-frequency generation unit for applying a high frequency to the excitation electrode while sweeping the frequency, and an electrically connected to the detection coil, and in the sample A moisture measuring device comprising: a measuring unit for measuring moisture.