SU363027A1 - CAPACITIVE MATERIAL HUMIDITY SENSOR - Google Patents

Description

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The invention relates to a measurement technique, in particular to capacitive humidity sensors of a material.

The known material moisture sensors containing a cylindrical insulating body, at the bottom of which there is a fixed disk electrode and a movable electrode placed inside the body, made in the form of a solid metal cylinder, do not have sufficient accuracy of measurement due to the influence of the thickness of the material under study.

To reduce the effect of the layer thickness of the material under investigation, the sensor proposed is equipped with an additional ring electrode located around the disk electrode outside the area of the material under study and forming a compensating capacitor with the moving electrode.

The drawing shows the sensor.

At the bottom of the cylindrical insulating body / there is a disk electrode 2. Inside the body there is a movable electrode 3, made in the form of a solid metal cylinder. An additional ring electrode 4 is located around the electrode 2 outside the area of the test material.

Between the outer surface of the moving electrode 3 and the surface of the electrode 2

an electric capacitance Srab is formed, the value of which depends on the position of the inner electrode 3 relative to the outer cylinder. The capacity will be the smaller, the larger the distance between the inner cylinder and the surface of the disk.

Another capacitor Sk is created between the surfaces of the electrodes 3 and 4. The capacitance Sk also decreases with increasing distance between

electrode surfaces 3 and 4.

It is necessary that with each lift of the inner cylinder, the containers Ck and Srab would be equal.

This can be achieved by selecting the ratio of the areas of the electrodes 2 and 4 of the ring and the disk, i.e. the area of the electrode 2 should be more than a few percent of the area of the electrode 4.

The sensor is pre-trigger for measuring the moisture content of a product that is cut by a disc-shaped ring, while it is difficult to establish a certain thickness of the product, which will interfere with accurate moisture detection, therefore the Srab capacitance is used to determine the disc-shaped product, and the capacitance Ck to compensate for its thickness.

The subject of the invention is a capacitive moisture sensor for materials containing a cylindrical insulating

a housing, at the bottom of which a stationary disk electrode is located and a movable electrode placed inside the case, made in the form of a solid metal cylinder, characterized in that, in order to reduce the influence of the thickness of the Investigated material layer, it is provided with an additional ring electrode located around the disk electrode outside the area placing the material under study and forming a compensating capacitor with a moving electrode.

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