RU2539125C1 - Device to measure parameters of dielectrics at ultrahigh frequencies - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: device comprises a microwave waveguide, a resonator with a cylindrical part limited at one side by the end wall of the microwave waveguide, and at the other side with a shorting piston with the ability of axial displacement inside the resonator, a piston displacement mechanism and a unit of radio measurement equipment. At the same time the microwave waveguide, the resonator cylinder and the displacement mechanism are installed in a single cylindrical body. The resonator cylinder is installed inside the body with the possibility of axial displacement and is equipped with clamps for fixation in the body, and the piston by means of the stem is fixed on the platform of the axial displacement module with a drive from a servomotor combined with the metre of linear displacement. The servometer is equipped with a system of automatic control connected with a radiometric block of fixation of resonant position of the piston.

EFFECT: increased accuracy of measurement of dielectric parameters and automation of a measurement process.

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Description

The invention relates to techniques for measuring dielectrics by the cavity resonator method at normal temperature.

A known measuring cell for measuring the parameters of dielectrics in the microwave, utility model RU No. 24292 U1, G01R27 / 26, comprising a housing and a cylindrical resonator mounted on it, the axis of which is vertical, the upper end of the resonator is closed by a fixed cover, which is the upper end wall of the resonator, the coupling elements of the resonator with the microwave path are located on the upper end and / or cylindrical wall of the resonator, the lower end wall of the resonator is formed by a piston mounted on a vertical rod, inside of which a channel for installing a thermocouple can be made, the rod is mounted and mounted on the end face of the vertical lead screw of the first screw pair, while the nut of the first screw pair is connected to the drive mechanism and rotated in a cage on the lower end of the shell having a smooth inner surface and covering a guide fixed to the housing, located coaxially with the resonator and having an internal cavity, moreover, a loading window for installing a sample of the test material is made in the lower part of the cylinder the cavity of the resonator or in the upper part of the guide, and on the outer surface of the guide there is a self-braking thread, and on the lower end of the shell is rotatably fixed a nut equipped with a gear rim, which forms a second screw pair with the guide, while the shell is kept from rotating around the guide by known methods .

In the presented device there are two complex mechanisms with manual control for moving the piston with the studied sample of material. The first is for the accelerated movement of the piston, used in the preparatory operations of installing the sample on the piston, and the mechanism for accurately moving the piston in the volume of the resonator during the measuring procedure.

The disadvantage of this solution is the use of a complex combined mechanism to ensure the process of measuring the dielectric parameters of samples of various materials, which leads to a decrease in the measurement accuracy, since before starting the measurement, the piston is set to the position corresponding to resonance in the resonator without a sample, at which a resonance is observed at a certain length fixed frequency. After that, the piston is moved down to install a sample of the test material through the loading window. The required piston stroke is significant, therefore, an additional mechanism for accelerated movement is used, which has worse accuracy and a large backlash, which introduces an additional error in the final results. After installing the sample, the piston, with the sample, moves to the measuring zone of the resonator, above the initial position. The geometric difference between the initial position of the piston in the resonant position and the position of the piston with the sample determines the dielectric constant of the test material.

Closest to the technical solution is a device for measuring the parameters of dielectrics on a microwave, USSR author's certificate No. 1737327 A1, G 01R27 / 26 of 05.30.92. The device includes a cylindrical resonator made with the possibility of axial movement and limited on one side by the fixed end wall of the microwave waveguide, and on the other by a short-circuit piston on which the sample of the material under study is located, while the piston is mounted on a rod with axial movement. The connecting link ensuring the coaxial position of the microwave waveguide, resonator, and axial displacement mechanism is a bracket, which also provides one-sided access to the resonator cylinder and then to the piston for specimen installation.

The operation is performed manually and there is no fixation of the cylindrical part of the resonator in any given position. The piston with the sample is moved to the resonant position in the device in question by a screw mechanism.

The disadvantage of this device is that to achieve high accuracy in determining the dielectric constant by the resonator method, it is necessary to maintain the constant geometric dimensions of the cavity of the resonator during measurement. The design of the presented device is made so that it is impossible to unambiguously install the cylindrical part of the resonator before and after the operation of installing the sample on the piston, since there are no devices that rigidly fix the cylindrical part of the resonator relative to the axis.

The disadvantage of the device in question is that the accuracy of measuring the resonant length of the resonator is determined by the accuracy of fixing the position of the sample through the use of a screw mechanism. This device also lacks a direct measurement of the linear displacement of the rod with the sample, which does not allow for multiple reproducibility of the installation of the piston in a predetermined position. In addition, the conventional screw pair used in the device for measuring dielectric characteristics by varying the length of the resonator, due to the inevitable play in the thread, does not provide the necessary accuracy for positioning the piston with the sample and, as a result, invalid measurement errors arise.

The aim of the invention is to improve the accuracy of measurements and reduce the time of operations due to the automation of the process of measuring dielectric characteristics.

The goal is achieved by the fact that the proposed device for measuring the parameters of dielectrics at microwave frequencies, including a microwave waveguide, a resonator with a cylindrical part, limited on one side by the end wall of the microwave waveguide, and on the other hand by a short-circuit movable piston mounted with axial movement inside the resonator, a mechanism displacement of the piston and radio measuring equipment, characterized in that the microwave waveguide, the cylinder of the resonator and the displacement mechanism are placed in a single housing, and the resonator cylinder is mounted axially movable inside the housing and equipped with clamps for fixing in the housing, and the short-circuit piston is fixed via the rod to the axial displacement module platform, controlled by a servomotor and combined with a linear displacement sensor, while the servomotor is equipped with an automatic control system, associated with the radiometric unit for fixing the resonant position of the piston.

When analyzing the operation of the experimental prototype, the authors found that the inventive device having the presented set of design features provides a more accurate measurement of the resonant length in the resonator compared to the prototype, which increases the accuracy of determining the dielectric characteristics of the materials under study. In addition, a distinctive feature of the device is that the measurement process is carried out automatically.

The drawing shows a General view of the claimed device.

The design of the device for measuring dielectric parameters includes a housing 1, a dielectric input 2 is placed in the upper part of the housing. A copper cylinder of the resonator is installed inside the housing with a minimum clearance (up to 0.005 mm). Clips 4 are connected with the resonator and have the ability to fix in the longitudinal grooves of the housing. The copper piston 5 is connected to the rod 6, which is fixedly mounted on the platform 7 of the axial displacement module 8, controlled by a servomotor 9. A micrometer reading of the movement of the piston with the sample 10 provides a linear distance meter 11 having a resolution of up to 0.1 μm, and the fixed piston 5 is connected with a rod 6, which is fixedly mounted on the platform 7 of the axial displacement module 8, controlled by a servomotor 9. A micrometer reading of the movement of the piston with the sample 10 provides a linear distance meter 11, Commercially resolution up to 0.1 mm and fixedly mounted on the platform module 8. linear movement for installation and the recess provided in the housing sample loading hole 12 of appropriate dimensions.

A device for measuring the parameters of dielectrics works as follows.

Before starting the measurements, the piston 5 is installed opposite the loading window 12 of the housing 1. By means of the clamps 4, the resonator 3 rises upward, and access to the piston for installing the test sample on it is opened. Then the resonator 3 is lowered down to completely overlap the boot window 12 and fixed with clamps 4.

Further control of the measurement process is carried out automatically (in standalone mode) by block 13 according to a program linking the activation of the servomotor 9, linear displacement module 8 and linear distance meter 11. The operation of these mechanisms provides the necessary movement of the piston with the sample to the resonant position “L”, recorded by the formation unit and processing microwave signals 14.

The dielectric constant "ε" of a material is measured by measuring the difference in length "L" without a sample and with a sample mounted on the piston. From the obtained values of the difference in the resonance length, the dielectric constant is determined analytically.

The inventive design of a device for measuring the parameters of dielectrics differs from the known analogues in higher measurement accuracy and a significant reduction in time to conduct a measurement cycle.

Information sources

1. Certificate for utility model No. 24292 U1 RU dated 11/13/2001 IPC G01R 27/26.

2. Copyright certificate of the USSR, No. 1737327 A1 IPC G01R 27/26 dated 05/30/92 /.

Claims (1)

A device for measuring the parameters of dielectrics at microwave frequencies, including a microwave waveguide, a resonator with a cylindrical part, limited on one side by the end wall of the microwave waveguide, and on the other hand by a short-circuit piston with axial movement inside the resonator, a piston moving mechanism and a block of radio measuring equipment, characterized in that the microwave waveguide, the cylinder of the resonator and the movement mechanism are installed in a single cylindrical body, and the cylinder of the resonator is installed inside the It is axially movable and equipped with clamps for fixing in the housing, and the piston is fixed via a rod to the platform of the axial displacement module driven by a servomotor combined with a linear displacement meter, while the servomotor is equipped with an automatic control system associated with a radiometric block for fixing the resonant position of the piston .