UA136579U - HIGH FREQUENCY VIDEO CURRENT CONVERTER - Google Patents

Abstract

The high-frequency eddy current converter consists of a winding inductance of the sensing element, which is included in the resonant circuit of the autogenerator on a transistor with a feedback capacitor, the resonant circuit of the autogenerator, in addition to the inductance of the sensing element, includes a capacitor. Additionally, a second transistor is introduced. The first and second transistors create a balanced stage, one of the outputs of which is the output of the eddy current converter.

Description

The useful model belongs to the means of eddy current control and can be used for the implementation of various non-destructive control devices (in particular, for measuring specific electrical conductivity, thickness of dielectric protective coatings, etc.) in aviation, energy, transport, oil and gas and chemical industries, etc.

Overhead eddy current converters of the transformer type are known, which consist of excitation windings and measuring windings. Known eddy current converters provide high sensitivity to defects in metal products and a high degree of damping of the influence of the change in the gap between the converter and the controlled surface, provided that operating frequencies up to 4 MHz are used (1, 21.

The disadvantage of known eddy current converters is the impossibility of their operation at high operating frequencies of more than 10 MHz due to the influence of the impedance of the cables connecting them to the eddy current control device.

Eddy current control devices are known, in which the converter consists of one inductive winding of a sensitive element, which is included in the resonant circuit of an autogenerator built using a transistor |Z, 4). These technical solutions have been successfully used to build eddy current flaw detectors, which are indicator-type devices and operate at operating frequencies up to 5 MHz |5I.

The disadvantage of the known devices is the limited possibility of increasing the operating frequency, even if an active eddy current converter is created according to this scheme by placing the autogenerator closer to the inductive winding directly in the sensor housing.

In addition, the known devices do not have sufficient stability, due to which they can be used to a limited extent for the construction of measuring devices for eddy current control (for example, for measuring the specific electrical conductivity or the thickness of the dielectric coating).

The closest analogue to the proposed useful model is the well-known eddy current converter, which consists of one inductive winding of a sensitive element, which is included in the resonant circuit of a two-circuit autogenerator on transistor b, 7). In known eddy current converters, the autogenerator circuit is located in the sensor housing next to the inductive winding of the sensitive element, which made it possible to reduce the influence of the cable impedance and successfully use them to create eddy current structurescopes operating at increased operating frequencies up to 400 MHz b, 71.

The disadvantage of the known device is low stability (in particular, temperature), which limits the accuracy of control due to the existence of an additional error.

The task of the proposed method is to increase the temperature stability and accuracy during the measurement of the parameters of the control object.

The problem is solved by the fact that in the high-frequency eddy current converter, which consists of the inductance winding of a sensitive element, which is included in the resonant circuit of the autogenerator on a transistor with a feedback capacitor, and in the resonant circuit of the autogenerator, in addition to the inductance of the sensitive element, there is a capacitor, additionally introduced the second transistor. The first and second transistors create a balanced cascade, one of the outputs of which is the output of the eddy current converter. The first and second transistors can be turned on, in particular, according to the scheme with a common emitter. The emitters of both transistors are interconnected and connected through a bias resistor to the common bus. The bases of the transistors are interconnected. The inductance winding of the sensitive element is connected to the base of the first transistor, and the other end of the inductance winding of the sensitive element is connected to the common bus through the resonant circuit capacitor and through the feedback capacitor to the collector of the first transistor. The output of the high-frequency eddy current converter can be the emitters of the first and second transistors or the collector of the second transistor. At the same time, the value of the temperature coefficient of the capacitor of the resonant circuit and the feedback capacitor should be chosen opposite and close in absolute values.

The drawing shows the scheme of the proposed high-frequency eddy current converter.

The proposed high-frequency eddy current converter (see drawing) consists of an autogenerator built on two transistors Mi and Me, which form a balance cascade. For this, transistors Mi and M" are included according to the scheme with a common emitter.

The emitters of the transistors are connected to the common bus through the bias resistor P", and the bases of the Mi and Ma transistors are connected to each other. Resistor Fk sets the mode of operation of the transistor Mi, which is necessary to ensure the conditions for generating oscillations of the autogenerator. The inductive winding 60 of the sensitive element is connected to the base of the first transistor M: and together with the capacitor Sk forms a resonant circuit of the autogenerator. The phase balance to ensure the generation of the autogenerator is provided by the feedback capacitor Сf, which connects the resonant circuit to the collector of the first transistor. The output of the high-frequency eddy current converter can be the emitters of the first and second transistors or the collector of the second transistor. At the same time, it is advisable to choose the parameters of the resonance circuit capacitor Sk and the feedback capacitor Сf opposite and close in terms of the absolute values of the temperature coefficient of capacitance.

Let's consider the operation of the proposed high-frequency eddy current converter on the example of its use to determine the thickness of dielectric protective coatings of metal structures. During operation, the eddy current converter is installed on the dielectric coating of the electrically conductive (metal) object of control, so that the inductive winding Io of the sensitive element interacts with the electrically conductive material of the object of control through a layer of dielectric coating. It is assumed that the high-frequency eddy current converter due to the construction of an autogenerator circuit ensures the generation of oscillations in the winding of the sensitive element, which is achieved in particular by choosing the appropriate mode of the transistor Mi, by choosing the value of the resistor Vk. Eddy currents are excited in the electrically conductive material of the object of control with the help of the variable electromagnetic field of the inductive winding Io (drawing). At the same time, due to the interaction of the inductive winding of the sensitive element with the electrically conductive material of the control object, its impedance (in particular, inductance) changes. These changes depend on the specific electrical conductivity and magnetic permeability of the material of the control object, as well as on the thickness of the dielectric coating. At the same time, by choosing a high operating frequency (more than 5 MHz), it is possible to reduce the influence of the electrophysical parameters of the material of the control object, in particular, the specific electrical conductivity of non-magnetic materials, such as aluminum and titanium alloys, etc. The sensitivity of the impedance of the winding of the sensitive element to changes in the thickness of the dielectric coating, on the contrary, increases. Since the inductive winding Go of the sensitive element is a component of the resonant circuit, which, in addition to the winding Io, includes the capacitor Sk, changes in the inductance of the winding Io lead, in particular, to a change in the frequency of the output signal of the autogenerator built on two transistors Mi and M»e, which with a capacitor The feedback loops form an autogenerator built in the form

From the balance cascade (see drawing). The selection of the capacitance of the feedback capacitor Сf is important for the formation of oscillations of the autogenerator, as it ensures phase balance. This construction of the autogenerator in combination with the selection of the parameters of the resonant circuit capacitor and the feedback capacitor, which should be opposite and close in terms of the absolute values of the temperature coefficient of capacitance, ensure high temperature stability of the proposed high-frequency eddy current converter, which is especially important when working at high operating frequencies (above 5

MHz). The output signals in our example in the drawing are taken from the common point of the emitters of the first and second transistors and registered by the corresponding circuit of the device (not shown). In principle, the output signal can be removed from the collector of the second transistor. The frequency of the output signal of the autogenerator correlates in our example with the thickness of the dielectric coating, the change of which changes the impedance (in particular, the inductance) of the inductive winding of the sensitive element.

Calibration of the external device for determining the thickness of dielectric coatings is carried out using appropriate measures of the dielectric coating in the measurement range.

During operation, the operator-controller installs a transducer with a high-frequency eddy current converter on the surface of the control object and registers the thickness value on the device's indicator.

The proposed high-frequency eddy current converter has high temperature stability due to its implementation according to the scheme of the balanced cascade and the appropriate selection of the parameters of the resonant circuit and feedback elements. The proposed converter is easy to implement and configure. This made it possible to successfully use it to create high-precision eddy current control devices.

Sources of information: 1. A.S. 1767409 USSR, MKY SO1M 27/90. Eddy current converter / V.N. student,

Yu.S. Grabsky. - MO 4869272/28; Announced on 07/19/90; Publ. 07.10.92, Bull. Mo. 37. 2. Pat. 102585 of Ukraine, IPC SO1M 27/90. Overhead eddy current converter / V.M.

Scholar - application Mo a 2011 10512; Application 30.08.2011; Publ. 25.07.2013, Bul. Mo 14. - 4 p. 3. Pat. 39217 of Ukraine, IPK SO1M 27/00. Eddy current autogenerator flaw detector /

V.M. Uchanin, V.V. Cherlenevskyi. - May 2008 12095; Application 13.10.2008; Publ. 10.02.2009, Bull.

Mo 3.

4. Pat. 39207 Ukraine, IPK SO1M 27/00. Eddy current flaw detector / V.M. Uchanin, V.V.

Cherlenevskyi. - application May 2008 11903; Application 07.10.2008; Publ. 10.02.2009, Bull. Mo 3. 5. Uchanyn V.N., Derecha V.Ya. The eddy current method of detecting surface defects of aircraft components in operational conditions // Techn. diagnostics and non-destructive testing. - 2006. - Mo. 4. - P. 20-28. 6. Ospapip M. Eiemaied ERgediepsie5 ip Edau Sitepib-Mem/ Rozviriiiyev oi Tip 5ipase Iauyeg

Emainayop // 15-1n MUopa Sopiegepse op Mopaevzigisiime Teziipud. - Vote, 2000. - Access mode:

Реru/lmmliu. bye bye 7. Mechanics of destruction and strength of materials: Evidence, manual. under general ed. V. V. Panasyuk. - Volume 9: Strength and durability of aviation materials and structural elements / O.P. Ostash, V.M.

Fedirko, V.M. Uchanin and others. - Lviv: SPOLOM, 2007 (p. 807, fig. 6.117).

Claims (5)

USEFUL MODEL FORMULA 1. High-frequency eddy current converter consisting of the inductance winding of a sensitive element, which is included in the resonant circuit of the autogenerator on a transistor with a feedback capacitor, in the resonant circuit of the autogenerator, in addition to the inductance of the sensitive element, a capacitor is included, which differs in that the circuit of the high-frequency of the eddy current converter, a second transistor is additionally introduced, the first and second transistors create a balanced cascade, one of the outputs of which is the output of the eddy current converter. 2. The high-frequency eddy current converter according to claim 1, which is characterized by the fact that the first and second transistors are connected according to the scheme with a common emitter, the emitters of both transistors are interconnected and connected through a bias resistor to the common bus, the bases of the transistors are interconnected, the inductance winding of the sensitive element is connected to the base of the first transistor, the second end of the inductance winding of the sensitive element is connected to the common bus through the capacitor of the resonant circuit and through the feedback capacitor to the collector of the first transistor. 3. High-frequency eddy current converter according to claim 1, which differs in that its output is the emitters of the first and second transistors. 4. High-frequency eddy current converter according to claim 1, which differs in that its output is the collector of the second transistor. 5. High-frequency eddy current converter according to claim 1, which is characterized by the fact that the parameters of the resonant circuit capacitor and the feedback capacitor are chosen to be opposite and close in absolute values of the temperature coefficient of capacitance. še KK; I Ok se i OK z sche din kkhzhky nka z y, okkzhkzhkyuyuky z He uh i; o o KZ m ANU t y p yd pz I I I Hokkkyuyuyuukkkkkkkkkyu ok Kok kn KK DYKU. sk With no