SU1383189A1 - Moisture content variable-capacitance pickup - Google Patents

Description

(21) 4160972 / 31-25

(22), 10/08/86

(40) 03/23/88. Bul No. L

(71) Institute of Automation, KirgSSR Academy of Sciences

(72) A.V.Kudr vtsev, V.N.Shevchenko and D.Sh.Ibraev

(53) 551.508.7 (088.8)

(56) USSR Author's Certificate No. 830225, cl. G 01 N 27/22, 1981.

USSR Author's Certificate number 1033866, cl. G 01 N 27/22, 1983.. (54). CAPACITY HUMIDITY SENSOR

(57) The invention relates to a measurement technique and can be used to measure the moisture content of various bulk and fibrous materials of uniform size and density, such as tobacco leaf.

cotton, raw wool, etc. The purpose of the invention is to increase the measurement accuracy. To this end, a more uniform compaction of the sample of material in the working area of the sensor is created due to the use of a base in the sample chamber consisting of separate sections, each of which is connected to the bottom of the chamber by means of an elastic element. The measurement accuracy increases with a simultaneous increase in the sensitivity of the sensor, since in the working area of the sensor the uniformity of the sample of the monitored material increases due to the additional densification of the sample of material in areas with lower density. 2 hp f-ly, 7 ill.

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The invention relates to measuring technique and can be used to measure the moisture of various loose and fibrous materials of heterogeneous size and density, for example, pressed tobacco leaf, cotton, raw wool, etc. The purpose of the invention is to improve the measurement accuracy due to reducing the random component of the error due to the heterogeneity of the sample of the monitored material in the volume of the sensor from measurement to measurement.

Figure 1 presents the proposed sensor, a General view; 2 is a section A-A in FIG. 1 (without sample of controlled material); FIG. 3 shows an elastic deformable base section of the probe receiving chamber; Fig. 4 shows a partitioned base made of an elastic material, variant ;, here is a diagram of the placement of a compacted homogeneous sample of the material under test with the partitioned elastically deformable base of the sample receiving chamber; figure 6 - placement of compacted heterogeneous sample of the test material in the sensor with a rigid base of the sample chamber; in fig „7 - the same, with a sectioned elastically deformable base of the sample chamber.

The main sensor assemblies (Fig. 1) are the body, the sample sealing mechanism, and the measuring portion.

The sensor body (Figures 1 and 2) consists of parallel plates 1 and 2 mounted on racks 3. A recess 4 is provided on the bottom plate I, for mounting the sample receiving chamber 5 with samples of the material being tested 6 in a predetermined position. On the top plate 2 there is fastened a nut bushing 7, which serves to move the lead screw 8, and a bushing 9 for the guide rod 10 ..

The compaction mechanism of the sample, in addition to the lead screw 8 and the guide rod 10, includes a friction ball clutch of the Pi sealing rod 12 connected through the horn 13 to the lead screw S.

In the proposed construction of the sensor, the upper end of the lead screw 8 is tightly mounted onto the disk 14, on which axially through the sleeve 15

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and balls 1 6 a spring 17 acts. Adjusting the rotational force transmitted to the rod 12l and, consequently, the degree of compaction of the test material 6 in the sensor can be accomplished by selecting the elasticity value of the spring 17 and the degree of compression of the nut 18. The rotation of the coupling 11 is performed by the handle 19 flywheel.

The measuring part of the sensor includes a capacitive transducer, the electrodes 20 of which are located in the end portion of the sealing rod 12, and the sample receiving chamber 5, for example, rectangular (figure 2) or cylindrical. The transducer electrodes 20 are electrically connected to connector 21, to which a capacitive moisture meter (not shown) is connected.

At the base of the sample chamber 5, install the sections 22, which can move vertically relative to each other. Structurally, these sections can be implemented in various ways. The section (FIG. 3) may consist of a body with a hole in the lower part 23, into which the spring 24 is tightly seated. Its lower end is fixed in the lugs 25 of the plate 26. At the same time, several sections 22, for example, five, are fastened on the same plate (FIG. , 2). Plates 26, together with sections 22, are installed at the base of the sample chamber 5 and fastened to it with screws (not shown). The shape of sections 22 in horizontal sections can be in the form of a square, a hexagon, a rhombus, a segment (with a cylindrical shape - a sample-receiving chamber), etc.

The base sections 22 can be made of an elastic material, for example, rubber (figure 4). Sections 22 are made of solid material by. cutting it through slots 27 in height to 80-90% of the total height. In this case, each of the sections 22 may be compressed to a considerable part of its height without additional deformation of the adjacent sections. The latter option is easier to manufacture, but it is more difficult to find the necessary degree of elasticity of the material. The first option is more difficult to manufacture, but it is easier to select the necessary spring stiffness in sections. The number of sections in the base, their 30

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that, the range of displacements, the degree of elasticity of the springs, and other parameters are chosen experimentally depending on the properties of the controlled materials.

The sensor works as follows.

A sample of the material to be tested 6 is placed in the sampling chamber 5, fill it no less than 3/4 of the volume, then it is installed in the recess 4 of the bottom plate 1 of the sensor base and rotating the handle 19 moves the sealing rod I2 downward until slippage occurs clutch 11 (or the target indicator of the pressure indicator will not be reached). This will ensure the required degree of compression of the material. The height of the compacted material sample is preselected experimentally and should not be less than the penetration depth of the electric field inside the material. Then, a capacitive moisture meter is connected to the connector 21 and, based on its indications, taking into account the preliminary calibration, or calculated by the method, find the humidity value of the monitored material.

An example of a positive effect in the proposed sensor can be judged by the following examples: with a uniform distribution of a homogeneous sample of material throughout the sample-receiving chamber (Fig. 5), the transfer of force from the sealing rod to each of the base sections occurs uniformly and, accordingly, the compression ratio of all springs the same. The latter should be selected within 40-45% of the full compression of the spring. If the distribution of the sample is controlled. Since the material in the sampling chamber is not uniform, and zones B are characterized by a higher packing density than zones B (Fig. 6), the sample heterogeneity in the working zone is preserved in the process of compacting the material in the sampling chamber with a rigid base. Since the number of zones with varying degrees of sample density varies from measurement to measurement, the random component of the error is also large.

If the base of the sample chamber is made in the form of elastic sections, the nature of the distribution of the sample of the test material in the working area

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The sensor after sealing changes. With an uneven initial placement of the sample material in the sample chamber transmitted from the seal-. Each of the sections (or groups of sections) is unequal (Fig. 7). In the places of more dense packing of the material sample (zone B) the pressure transmitted to section 22 is greater than in places with lower material density (zone B). Accordingly, the sections in individual sections are compressed to varying degrees: more in zones B, less in zones C.

This means that with a larger mass of a sample of material in zones B, the occupied volume (the product of the section area and the height of the material above it) is larger, while with a smaller mass in zones C, the volume occupied by the material, i.e. after compaction, the density of the sample of the monitored material is uniform, which leads to an increase in the measurement accuracy.

Thus, the proposed technical solution makes it possible to increase the measurement accuracy while simultaneously increasing the sensitivity of the sensor, since Kak in the working area of the sensor increases the uniformity of the sample of the monitored material due to additional compaction of the sample of material in areas with lower density.

Claims (2)

1. A capacitive humidity sensor containing a sampling chamber with a bottom, a sealing rod with scattered floor electrodes located in its front part, and an indicator of the degree of compression of a sample of a material, characterized in that In order to improve the measurement accuracy by reducing the random co-: / thrust error due to the uneven distribution of the sample of the monitored material in the working area, the sample-receiving chamber is equipped with an additional bottom, made as separate sections, with the possibility of pa- relative to each other in the direction of the applied efforts of the sealing rod by means of elastic elements. 2. A capacitance sensor in accordance with claim 1, in which, ka51383 A spring is used as the elastic element, with one end attached to the bottom of the chamber and the other end to separate sections of the additional bottom. B, The capacitive sensor according to claim 1, which is designed so that, in order to simplify manufacture, the individual sections are made of an elastically deformable material. /five Fy 22 fi9. f {4g. FIG.  AT FIG. 6 7