JPH0552798A - Sensor for moisture meter and method for measuring moisture using the same - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a sensor for a moisture meter that can reliably measure an object having a low water content such as powder, and can perform continuous measurement. thing. [Structure] The lower electrode 12 is formed on the lower surface of the insulating substrate 10, and the upper electrode 14 is formed on the upper surface of the insulating substrate. The lower electrode is formed so as to cover the entire lower surface of the insulating substrate, and the upper electrode is formed by the pair of comb-shaped electrode portions 16,
16 and tooth portions 16a, 16a of the comb-shaped electrode portions
Are inserted alternately. Further, the insulating film 18 is deposited on the upper surface of the upper electrode. This insulating film 1
8 is made of a water-resistant material having low water absorption, and for example, enamel, polyamide system, melamine resin and epoxy resin can be used. Then, for measurement, the object to be measured is placed on the upper surface of the sensor. Then, the capacitance between both comb-shaped electrode portions changes according to the water content of the measured object.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor for a moisture meter and a moisture measuring method using the sensor,
More specifically, the present invention relates to a measurement object suitable for a material having a low water content such as powder.

[0002]

2. Description of the Related Art A conventional moisture meter is a capacitance type,
There are various types such as heating method and infrared absorption method. Then, for example, as the electrostatic capacity method, a sensor as shown in FIG. 5 is used. That is, in this sensor, a lower electrode 2 composed of a pair of comb-shaped electrode portions 2a, 2a is provided on the upper surface of a glass substrate 1, and a polymer film 3 of acetate, cellulose or the like is provided so as to cover the upper surface of the lower electrode 2. ,
Further, an upper electrode 4 is provided on the upper surface of the polymer film 3. Then, a pair of electrode portions 2a forming the lower electrode 2,
Lead wires 5 are connected to the ends of 2a, respectively.

Considering an equivalent circuit of such a structure, a capacitor is formed between each electrode portion 2a and the upper electrode 4, and finally, a circuit in which two capacitors are connected in series between the lead wires 5 and 5. Furthermore, the dielectric constant of the polymer film 3 changes as it absorbs and releases water. Therefore, since the polymer film 3 has a predetermined amount of water according to the moisture content of the atmosphere in which the sensor is placed, that is, the humidity,
Humidity is detected by detecting the capacitance between the lead wires 5 and 5.

In addition, the so-called heating method is also used. First, a predetermined amount of powder, which is an object to be measured, is weighed, and then the powder is heated to evaporate water present in the powder. Then, the weight of the powder after heating is measured again. Then, the water content is measured from the measurement results (weight) before and after heating.

Further, the so-called infrared method is a method of irradiating an object to be measured with infrared rays and measuring the water content from the absorption rate of the infrared rays at that time.

[0006]

However, the above-mentioned conventional measuring methods have the following problems, respectively. That is, the capacitance method shown in FIG. 5 is not suitable for measuring the water content of the powder or the like, which is the object of the present invention, because the measurement object is exclusively gas.

Further, in the case of the heating method, heat treatment is required, and the measurement must be performed before and after the heat treatment, which is not only complicated in many working steps but also requires a relatively long measurement time. It costs. Furthermore, when a powder is adjusted to a desired water content, a heating method is used as a means of checking the water content, and once the water content is adjusted, the water content is measured to obtain a predetermined water content. If not, the powder adjustment must be restarted from the beginning. That is, there is a problem that continuous measurement such as performing measurement while performing adjustment work cannot be performed.

Further, the infrared type is suitable for a relatively high water content of 10% or more, but is in a low water content range of several% or less, which is the object of the present invention. Then, there is a problem that reliability is low and reproducibility is not obtained.

The present invention has been made in view of the above background, and an object of the present invention is to reliably measure a substance having a low water content such as a powder, Moreover, it is to provide a moisture meter sensor capable of continuous measurement and a moisture measuring method using the sensor.

[0010]

In order to achieve the above object, in a sensor for a moisture meter according to the present invention, an upper electrode and a lower electrode are arranged to face each other via an insulating member, and the upper electrode has a predetermined size. The upper electrode was composed of a pair of electrode portions spaced apart from each other, and the upper surface of the upper electrode was covered with an insulating layer having water resistance.

Further, in the moisture measuring method using the moisture measuring sensor, an object to be measured is placed on the upper surface of the moisture measuring sensor having the above-mentioned structure, and the electrostatic capacitance between the measuring object and the upper electrode is set. The water content of the measurement object was determined from the capacitance and the capacitance between the upper electrode and the lower electrode.

[0012]

Function: An object to be measured such as powder is placed on the upper surface of the sensor. At this time, since the insulating layer is interposed between the DUT and the upper electrode, the two do not become conductive.
Therefore, since the capacity between the pair of electrode portions varies depending on the water content of the placed object to be measured, the water content of the object to be measured can be detected by measuring the capacity. Further, since the insulating layer is made of a material having water resistance, the moisture content of the atmosphere or the moisture of the measured substance does not soak into the insulating layer. It will be that of the measurement object.

[0013]

EXAMPLES Preferred examples of the moisture sensor according to the present invention will be described below. First, as shown in FIG. 1, the lower electrode 12 is formed on the lower surface of the insulating substrate 10.
An upper electrode 14 is formed on the upper surface of 0. The lower electrode 12 is formed so as to cover the entire lower surface of the insulating substrate 10. The upper electrode 14 is composed of a pair of comb-shaped electrode portions 16 and 16 and has a shape in which the tooth portions 16a and 16a of the comb-shaped electrode portions 16 and 16 are alternately inserted and arranged. In this example, a so-called double-sided printed circuit board is used to form the upper electrode 14 having a predetermined shape by etching or the like. For example, the electrodes 12, 14 are formed by vapor deposition on the surface of the insulating substrate. However, the manufacturing method is arbitrary.

Further, in the present invention, an insulating film 18 is deposited on the upper surface of the upper electrode 14. This insulating film 18 is
It is made of a water-resistant material having low water absorption, and for example, enamel, polyamide, melamine resin and epoxy resin can be used. In this example, the insulating film 18 is formed so as to cover not only the upper electrode 14 but also the entire upper surface of the insulating substrate 10, but the present invention is not limited to this, and at least covers the upper surface of the upper electrode 14. All you have to do is

Furthermore, in this example, the end portions of the comb-shaped electrode portions 16 and 16 constituting the upper electrode 14 and the lower electrode 12 are formed.
The lead wire 20 is connected to each.

Next, a preferred embodiment of the moisture measuring method according to the present invention using the above-mentioned sensor will be described. In this example, in order to measure the above capacity using an LCR meter, a measuring device as shown in FIG. 2 is used. That is, the basic clock generated by the rectangular oscillation circuit 22 is amplified by the driver amplifier 24 to define the amplitude, and the amplitude is supplied to one comb-shaped electrode portion 16 of the sensor 26. Then, after the waveform output from the other comb-shaped electrode portion 16 is passed through the smoothing circuit 28 to be converted into an effective value, the amplifier 30
The signal is amplified to a value that can be detected via and output as a voltage. At this time, the lower electrode 12 is connected to the ground via the lead wire 20. In the figure, the capacitor C1 indicates the capacitance between the lower electrode 12 and the comb-shaped electrode portion 16, and the capacitor C2 indicates the capacitance between the pair of comb-shaped electrode portions 16 and 16.

In order to actually perform the measurement using the apparatus having such a configuration, first, as shown in FIG. 3, an appropriate amount of the ferrite powder 32 as the object to be measured is placed on the upper surface of the sensor 26. Then, the insulating film 18 and the ferrite powder 32 are present between the comb-shaped electrode portions 16 and 16, and since the insulating film 18 is made of a material having good water resistance, the moisture content of the ferrite powder 32 is eventually increased. Accordingly, the capacity of the capacitor C2 changes. Therefore, by previously investigating the relationship between the capacity (output voltage) and the water content and forming a correlation diagram, the water content of the ferrite powder 32 can be detected by simply measuring the capacity thereafter.

* Experimental Results Electrodes having a predetermined shape were formed on both surfaces of the glass epoxy. The upper electrode has an electrode width of 1 mm and both comb-shaped electrode portions 16 and 1
The gap between 6 is about 0.47 mm, the total number of teeth 16a is 52, and the no-load capacitance of the sensor on which the measured object is not placed is 180 pF. As the object to be measured, manganese-based ferrite powder mixed with a binder, a surfactant, tap water, etc. was used. Then, the object to be measured was placed from the upper surface of the sensor at a height of about 5 mm and stirred in the horizontal direction so that the object to be measured was uniformly present on the sensor. Then, the water content was changed and the water content of the sample at a predetermined volume was measured. The results are shown in the table below. In addition, the capacity measurement is performed using an LCR meter,
The measurement frequency was 1 kHz.

[0019]

[Table 1] 220pF 290pF 300pF 350pF 400pF 500pF 700pF 800pF Sample 1 0.27% 0.51% 0.54% 0.71% 0.88% 1.22% 1.90% 2.25% Sample 2 0.25% 0.44% 0.46% 0.60% 0.73% 1.00% 1.54% 1.81% Sample 3 0.36% 0.53% 0.55% 0.67% 0.79% 1.03% 1.51% 1.75% Samples 1, 2 and 3 in the table have different composition ratios of ferrite powder. Then, based on the above measurement results, a correlation diagram is formed, which is shown in FIG. As is clear from the above table and FIG. 4, when the water content is several% or less, almost the same characteristics can be obtained regardless of the sample. Therefore, the water content of the object to be measured can be detected from the correlation shown in FIG. 4 simply by measuring the capacity thereafter.

Next, an example in which the above measuring method is applied to an actual manufacturing process of ferrite powder will be described. Install the above-mentioned measuring sensors in several places inside the mixer for mixing and adjusting ferrite powder. Then, water is supplied and stirred in the mixer. At this time, the capacitance is simultaneously measured using the plurality of sensors, and each measured value is averaged. By doing so, the water content can be measured while performing the stirring process, so that the amount of water supplied can be adjusted while observing the water content. That is, continuous measurement is possible. The stirring time of the mixer can be determined by the deviation of the measurement value obtained from each sensor. That is, the fact that the deviation is small means that the mixture is uniformly stirred in the mixer.

The object to be measured is not limited to the above-mentioned ferrite powder, but it goes without saying that it can be applied to, for example, concrete powder, foundry sand, ceramic powder and various other materials.

[0022]

As described in detail above, the sensor for a moisture meter and the moisture measuring method using the sensor according to the present invention continuously measure even if the object to be measured has a low water content such as powder. Measurements can be made. Since the insulating layer is interposed between the upper electrode and the object to be measured, the object to be measured can be measured even if the material has high conductivity.
Furthermore, since the insulating layer is made of water-resistant material, the moisture content of the atmosphere and the moisture of the object to be measured will not soak into the insulating layer. It becomes a measurement object, and accurate measurement is possible.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a moisture sensor according to the present invention.

FIG. 2 is a block diagram showing an example of an apparatus for carrying out the moisture measuring method according to the present invention.

FIG. 3 is a front view showing the sensor during moisture measurement.

FIG. 4 is a graph showing measurement results.

FIG. 5 is a diagram showing an example of a conventional moisture meter sensor.

[Explanation of symbols]

 10 Insulating Substrate 12 Lower Electrode 14 Upper Electrode 16 Comb Electrode 18 Insulating Film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shozo Sakurai 5-36-11 Shinbashi, Minato-ku, Tokyo Fuji Electric Chemical Co., Ltd.

Claims (2)

[Claims] 1. An upper electrode and a lower electrode are arranged to face each other with an insulating member interposed therebetween, and the upper electrode is composed of a pair of electrode portions separated from each other at a predetermined interval, and the upper surface of the upper electrode is A sensor for a moisture meter, which is covered with an insulating layer having water resistance. 2. An object to be measured is placed on the upper surface of the sensor for a moisture meter according to claim 1, the capacitance between the object to be measured and the upper electrode, and the upper electrode and the lower electrode. A water content measuring method, wherein the water content of the object to be measured is obtained from the capacitance between the two.