SU1030715A1 - Capacitive flow-through type pickup - Google Patents

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 The invention relates to a measurement technology and can be used to control and automate and measure such parameters of substances as moisture, density, viscosity, composition, flux density and other hrukktion. associated with measurement of the dielectric constant or conductivity, as well as for the measurement of the electrification of dielectric l:} dyokotek and gases. A capacitive sensor, rj, from a housing with Flan1, is known to a sensitive element (multi-cylinder coaxial condensate, filled as a set of hollow cylindrical electrodes with alternating polarity, in which the electrodes are fixed by means of grounded metal clad. It and G1 thio:; com, electrically) isolated from the workers electro-electrical fluoroplastic coating Fri j j To the disadvantages of this sensor should be attributed to the power potential 1-. in ensuring the ground contact of the grounded ionics with e.pectrodes of the corresponding polarity. Moreover, it increases the hydraulic efficiency of the electrode area) and creates a siepaDi-ioMepHocTb electromagnetic field sensor, which is difficult to take into account when carrying out accurate measurements of the electrical characteristics of the gates, and the presence of dielectric plates of the electrodes the interelectrode space leads to a temperature dependence of the working capacity of the sensor. Also known is the capacitive flow sensor BecimomnocT-tj flow, consisting of a shell with flanges and a sensing element 1 of a multi-cylinder coaxial gas condenser; 4; , made in the form of two fully coaxial plates, the relative position of which is fixed by means of a sensor located in the center, a screw with an insulator, and an external INSULATOR and screen shield installed in the end part. rings 2. The disadvantages of this design are the difficulty of making one-piece coaxial plates of the condenser OB. as well as the error of the output signal caused by the influence of the temperature of the controlled and surrounding media due to radiation. 7: oracle in the center of the sensor, directly between the working electrodes ;. Constructions; nor does it provide adequate resistance to vibrations from the fact that ale.; the trodes are attached to the console. In addition, the electromagnetic field of such a sensor is uneven due to the presence of edge fields at the ends of the electrodes. The closest in technical essence to the present invention is a capacitive flow sensor containing a multi-cylinder condenser, run-. Installed in the form of a system of electrodes with current leads and leads located between a cross-shaped bases of electrodes, of which electrodes of one polarity are equipped with guard electrodes fixed by annular insulating gaskets located on the end portions of G. Constructive internal parasitic ones fields scattered in the working interelectrode gaps of the sensor, arising from the fact that the current conductors to the main and guard electrodes. The electrical electrical connection between them and the metal pins are fixed in the electrode holes in the radial: OM direction and therefore appear with a coaxial capacitor inserted in the field, which inevitably leads to an error in the analytical calculation of the initial capacitance of the sensor, and consequently to an error measurements. Along with this, the current leads of such a tie sensor are shielded from each other, and parasitic capacitance is formed between them, which also leads to measurement errors. In addition, the presence of gdgcfts leads to a decrease in the effective area of the electrodes, which, in turn, leads to a loss of sensitivity and an increase in measurement error, and the radial arrangement of the current leads complicates the process of assembling and disassembling the sensor, requires the development of special equipment for holes in the electrode .x, makes it difficult to unify the individual nodes of the sensor (in particular, the electrodes, makes it difficult to ensure reliable contact with the electrodes. The aim of the invention is to improve the accuracy measurements of the electrical properties of liquids and gases and improving the manufacturability of a capacitive flow sensor. The goal is achieved in a capacitive flow sensor comprising a housing and a multi-cylinder coaxial capacitor, made in the form of an electrode system with current leads and terminals , in which electrodes of one polarity are supplied with protective e.projects, fixed (for about 5 years at the ends of the annular insulating plates and, TOKOPO-7DVODY All groups of electrodes are brought to their frontal parts and fixed inside insulating liners, provided with centering grooves and installed in the cavity of metal fins of cruciform bases, and the current leads to the protected electrodes are passed through and isolated from the protective electrodes . Figure 1 shows a capacitive flow-through sensor, a general view, in section; Fig. 2 shows the circuit for mounting the lead from the electrodes through the holes in the guard electrodes); in Fig. 3, the design of the cross-shaped base, the view in Fig. 4 is section AA in Fig. 1. The sensor consists of a housing 1 with flanges, inside which a coaxial capacitor is fixed, consisting of hollow cylindrical electrodes 2 of one polarity, electrodes 3 of another polarity and guard electrodes 4. The mutual arrangement of guard electrodes and internal electrodes is fixed using insulating gaskets 5 placed in the grooves of these electrodes. The whole package of electrodes is assembled between two cruciform bases b with hollow ribs. Bases can be made by casting, or stamping. In the cavity of the ribs, insulating inserts 7 are inserted, which can also be made of fluoroplastic, fiberglass, ceramics, or other insulating materials. The inserts are provided with concentric centering grooves for the installation of electrodes and have openings 8 for current leads 9 connected to the temporary leads 10. Each base has three edges. The walls of each edge are used to shield only one pin, i.e. the output from the electrodes of one polarity passes through the cavity of the first edge, the output from the electrodes of the other polarity passes through the cavity of the second edge, and the output from the guard electrodes passes through the cavity of the third edge. The base, together with the package of electrodes, is fastened together with a collective hollow rod 11 with threaded ends and nuts 12 and 13 of a streamlined shape. The nut 13 is provided with a hole to lead the wires from the resistance thermometer 14 and at the same time creates a flattening of the sheath 15 through which these wires are passed. The plug 16 and the gasket 17 serve to seal the resistance thermometer. At the exit from the housing, the sensor leads are placed in cylindrical e.cranes 18, reinforced in the bases. The tightness of the outlets is created by means of bobs 19, gaskets 20, an installation of sealing sleeves 21 and glass bushing insulators 22 welded to the body. The output from the electrodes passes through an insulator 23 installed in the holes of the guard electrode. The device works as follows. The sensor is fixed by means of flanges to a pipeline with a controlled or studied medium. With the passage of the test medium in the space between the electrodes 2 and 3, a certain value of the sensor capacitance is established. Changes in the parameters of a flowing medium, such as composition, continuity of flow, density, viscosity and other, functionally related to electrical parameters of the medium, cause a change in capacitance, which is measured by an instrument connected to the terminals of the sensor, such as a bridge with close inductive coupling, allowing measure capacitance, conductivity or tangent of dielectric loss angle. The proposed capacitive flow sensor makes it possible to exclude from the measurement result parasitic capacitances formed by current leads to the working AND guard electrodes. This effect is achieved due to the fact that all of the CURRENTS passing through the cavities of the base edges independently of each other are shown by partially shielded metal walls of these bases which are electrically connected to the sensor body (screen. The arrangement of the current leads of the sensor in the ends of the electrodes allows ensure reliable contact with them, eliminate the error due to the non-uniformity of the electromagnetic field in the interelectrode space, create conditions for the uniform distribution of the controlled Thus, the proposed invention improves the accuracy of measurements of the electrical properties of liquid and gaseous substances, as well as improves the manufacturability of the sensor. The proposed sensor also allows you to expand the range of the measured dielectric constant by changing the initial capacitance using unified cylindrical electrodes of different diameters.

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Claims (1)

(.57) A CAPACITIVE FLOW SENSOR comprising a housing and a multi-cylinder capacitor made in the form of a system of electrodes with current leads and terminals located between the crosswise legs, in which the electrodes of the same polarity are equipped with guard electrodes fixed by ring insulating gaskets located on the end parts, characterized by the fact that, in order to increase the accuracy of measurement and improve the manufacturability of the Manufacture, the current leads to all electrodes are connected to their end parts and fixed inside When insulating bushings provided with centering grooves and mounted in the cavities of metal ribs cruciform bases, wherein current supply to the protection of _a ~ emym electrodes are passed through elongated holes formed in the guard electrodes and are insulated from them.