SU1659834A1 - Device for measuring dielectric parameters of materials - Google Patents

Abstract

The invention relates to instrumentation engineering and can be used in the construction of precision measuring devices for input dynamic control of dielectric parameters of tape and disk storage media. The purpose of the invention is to improve the accuracy of measurements in a dynamic mode by providing the required uniformity and intensity of an alternating electric field in the measurement zone and converting potential signals corresponding to the maximum values at the extremum points of the calibration characteristics of the sensors.

Description

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Potential electrodes 1 of two identical three-electrode sensors are connected to a harmonic generator 6, measuring and compensating 2 and 3 electrodes are connected to the outputs of differential amplifiers 7 and 8, the outputs of which are connected respectively through amplitude detectors 9 and 10 to the inputs of the adder 11 and comparator 12, the output of the adder 11 connected to the input of the traction detector 13, the output of which is connected to the input of the analog-digital converter 15, the output of the comparator The invention relates to the measuring and control technology and can be Used in the construction of precision measuring devices for input and dynamic control of dielectric parameters of tape and disk information carriers used in the technique of magnetic video recording.

The purpose of the invention is to improve the accuracy of measurements of the dielectric properties of a material in the dynamic mode of active control by implementing the required uniformity and intensity of an alternating electric field in the measurement zone, achieved by the construction features of the measuring sensors of the device, which are necessary to obtain subsequent effective transformations of potential signals corresponding to the maximum the values at the extremum points by the calibration output characteristic of the sensors.

FIG. 1a, b shows the design of the measuring sensor of the device; in fig. 2 is a block diagram of the device; in fig. 3 shows plots of stresses acting at certain points in the electrical circuit of the device for the mode of uniform motion of the measuring sensor in a direction orthogonal to the test surface.

A device for measuring the dielectric properties of materials includes two identical three-electron measuring sensors integrated into one unit (Fig. 1), where each of them contains a potential 1, a measuring 2, and 3 compensating electrodes enclosed in an external screen 4 and made in the form of thin metal disks of equal diameter, located on the surface of a rectangular plate 5 of an isotropic dielectric, the measuring sensor is placed so that its working plane, measure 12 is connected to the input of the one-shot 14, the output of which is connected to the second input of the traction detector 13, and the second output is connected to the second input of the analog-digital converter 15, the output of which is the output of the device, the sensors are made in the screen 4 connected to the common bus of the device, and the electrodes of the sensors are placed on the surfaces of the plate 5 of isotropic material, which are arranged parallel to one another in planes. 3 il.

each other at a distance not exceeding one tenth of the distance between the potential and measuring electrodes, in the process

The measurements are uniformly displaced parallel to the surface of the material under study.

The device also contains a generator of 6 harmonic oscillations, the first and second

differential amplifiers 7 and 8, first and second amplitude detectors 9 and 10, adder 11, comparator 12, peak detector 13, one-shot 14, analog-to-digital converter (ADC) 15, which are interconnected as follows.

The interconnected potential electrodes 1 of the measuring sensors are connected to the first output of the generator 6, the second output of which is connected to the common

by bus. Measuring 2 and compensating 3 electrodes are connected to the inputs of differential amplifiers 7 and 8, the outputs of which are connected through amplitude detectors 9 and 10 to the inputs of the adder 11 and

the comparator 12 connected to the inputs of the peak detector 13 and the one-shot 14, respectively, the output of the peak detector 13 is connected to the signal input of the ADC 15, the start input of which is connected to the output

one-shot 14, and the input of the installation of the detector 13 is connected to the second output of the single-vibrator 14.

The device works as follows.

By means of potential electrodes 1, connected to generator 6, an alternating electric field is created in the space between the working plane of each sensor and the surface to be monitored. The change in the intensity of this field in the gap due to the approach of the material under study to the sensors leads to a change in potentials over the surface.

their measuring electrodes 2. The output characteristics of electrostatic sensors, depending on the approach to them of the surfaces of dielectrics, have extreme values (minima) of the potential, therefore, the electrodes 2 at certain distances from the surface of the dielectric take these values. Subtracting the signals of electrodes 2 and 3 and the subsequent amplification of differential CHI with amplifiers 7 and 8, allows to obtain at their outputs maximum values of potentials at the moment when the output signals of the sensors are minimal. According to the results of experimental studies of electrostatic sensors, the signal from each of them at a certain distance interval takes the minimum value, which, as the sensor passes this distance, remains almost unchanged. This interval for the sensors under consideration is approximately one tenth of the distance between the centers of the potential 1 and measuring 2 electrodes of one of the sensors.

Thus, when both sensors are within the specified distance interval, their signals will be equal (Fig. 3A) and the output voltage of the adder 11 (Fig. 36) will be proportional to the sum of the voltages acting on its inputs, and at the output of the comparator 12 a Wits pulse (Fig. Sv), the leading edge of which will correspond to the moment of coincidence of the potentials of electrode 2. The one-oscillator 14, triggered by the pulse of the comparator 12, generates its own pulse (Fig. 3g) of the required duration arriving at the launch input The 15V transducer at the information input of the latter at this moment is affected by the measured voltage, the value of which is fixed by the peak detector 13, the memory mode of the detector 13 is set by a pulse from the output of the one-oscillator 14, which enters the installation input of the peak detector 13, for its duration ( Fig. Rear).

The output voltage of the device is represented at the output of the analog-digital converter 15 in the form of a binary code corresponding to a certain dielectric constant value.

All nodes of the functional circuitry of the device (Fig. 2) can be constructed according to standard radio circuits using integrated circuits.

The sensor unit is a metal case, which simultaneously plays the role of a screen, inside which electrostatic sensors (Figs. 1 and 2) are placed, which can move relative to each other and precisely fixed in any

position The rear values of the displacement of the working planes of the sensors are carried out using an ungrounded metal plate (since in this case the metal can be considered as a dielectric with

0, the dielectric constant Ј-, and the distance interval, with the passage of which the minimum values of the potentials of the measuring electrodes do not change, is the narrowest.

5 The use of the device, for example, in the equipment of the input control of tape media, in the SAR of video recorders or PEPNS (containing similar kinematic LSM nodes, on the quality and

Claims (2)

The reliability of which, to a certain extent, depends both on the level of technical and operational parameters and the service life of the recording media themselves) provides a noticeable improvement in the quality of data recording and reproduction. Precision contactless control of the dielectric parameters of information carriers, carried out in the active dynamic mode, is achieved (in comparison with a known device) without noticeable complication and cost of devices. Claim 1. Device for measuring the dielectric properties of materials, containing 5 two identical three-electrode measuring sensors, potential electrodes of which are interconnected, as well as with the output of a harmonic oscillator, the second output of which is connected to 0 common bus, measuring and compensating electrodes of each of the sensors are connected respectively to the inputs of the first and second differential amplifiers, the outputs of which are connected respectively 5 with inputs of the first and second amplitude detectors, characterized in that, in order to increase the measurement accuracy in the dynamic active control mode, an adder, a comparator, a peak detector, a one-shot and analog-to-digital converter are entered into it, the output of the first amplitude detector being connected to inputs of the adder and comparator, the second inputs of which are connected to the output of the second amplitude detector, the output of the adder is connected to the input of the peak detector, the output of which is connected to the signal input of the analog-digital a converter, the comparator output is connected to the input of monostable multivibrator, whose output is connected to the start-up input terminal of the analog-digital converter, the output of which is the output of the device, the second output of the one-oscillator is connected to the input of the installation of the peak detector, with the electrodes of each of the measuring sensors placed in a screen connected to a common busbar, parallel to each other Planes, distance between which does not exceed one tenth of the distance between FIG. g 0 centers of potential and measuring electrode sensor. 2. The device according to claim 1, wherein the electrodes of each of the measuring sensors are made in the form of thin conductive disks with equal diameters and are placed on the surfaces of rectangular dielectric plates of an isotropic material. Aa