RU1772731C - Device for recording acoustic emission signals - Google Patents

Abstract

The invention relates to a measurement technique. The purpose of the invention is to improve the accuracy and reliability of registration. Acoustic emission signals received are detected by a circuit enclosed in a shielded enclosure that is coupled to a cavity resonator. The signal changes the capacitance of the tuning element of its frequency, to the input of which a detected signal is supplied. A change in the tuning frequency of the resonator detects a change in the voltage of the acoustic emission signal. 1 ill.

Description

The invention relates to control and measuring equipment, namely, devices for research and control of materials and products using the acoustic emission phenomenon, and can be used in materials research and control of manufacturing processes of products in production conditions characterized by a high level of electromagnetic interference, leading to a malfunction of the equipment, especially when it is necessary to register weak acoustic signals.

A device is known for recording acoustic emission signals, comprising a shielded housing, an amplifier placed therein, an electro-acoustic transducer connected to it, and a recorder {1}.

The disadvantage of this device is the low reliability of signal registration, due to the fact that

shielded housing does not preclude interference from the mains.

The closest in technical essence is a device for recording acoustic emission signals, comprising a shielded enclosure, a serially connected amplifier, an amplitude detector, an amplifier of the detected signals and an electromechanical transducer, the membrane of which is located in the wall of the enclosure, is electrically connected to the latter and made from an electrically conductive ferromagnetic material, a unit for converting membrane vibrations into electrical signals connected to it ln amplifier, the output of which is connected to the recorder. In this case, the unit for converting membrane vibrations into electrical signals is made photoelectric with a shutter rigidly connected to the outer side of the membrane {2}.

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A disadvantage of the known device is the large non-linearity of inertia, low vibration resistance and sensitivity, which does not allow for high accuracy of measurement and control of the properties of the object under study. The inertia is due to the electromechanical principle of converting the oscillations of the membrane into an electrical signal, which is realized due to the deflection of the membrane and the displacement of the damper. A flat membrane has a nonlinear dependence of the magnitude of the deflection on the acting force, which leads to large measurement errors. Vibration resistance is hindered by the fact that the shutter attached to the membrane can be shifted due to vibration relative to the light source and the photodetector, causing an interference signal, which leads to an increase in the error.

The aim of the invention is to increase the accuracy and reliability of registration by increasing the linearity of conversion, speed, vibration resistance and sensitivity.

To achieve the specified circuit in the device for recording acoustic emission signals containing

a converter and a shielded case with an amplifier placed in series connected to it, the input of which is connected to the converter, an amplitude detector, and an amplifier for detecting signals, and a recorder, a recorder is made in the form of a volume resonator of electromagnetic field oscillations with an electronic frequency tuning element, the input of which connected to the output of the amplifier detected signals.

The exclusion of a membrane driven by an electromagnet to convert an informative signal, and the use of a resonator with high-speed electronic tuning for this purpose significantly reduces the inertia and, consequently, the dynamic error, as well as the high degree of non-linearity of the transformation due to the shape of the static characteristic of a flat membrane. Elimination of the electronic signal converter connected to the membrane increases vibration resistance and reduces interference causing additional errors in the prototype, and replacing the mechano-optical converter of the informative signal with an electronic converter with a large slope of the dependence of the output parameter (microwave frequency

electromagnetic field of the cavity resonator) from the input (electrical analogue of acoustic emission signals) makes it possible to increase the sensitivity of the device.

The invention is explained in the description of a specific example of the implementation of the device, a schematic diagram of which is shown in the drawing.

Signal Recorder

0 acoustic emission contains a shielded housing 1, equipped with a volume resonator 2 of the oscillations of the electromagnetic field, in which there is an element 3 (for example, varicap) electronic adjustment

5 natural frequency of the resonator. An electric signal amplifier 5, an amplitude detector 6 and a detected signal amplifier 7 are connected in series with an electro-acoustic transducer in series. To generate electromagnetic oscillations in the resonator 2, a tunable generator 8 with a modulator 9 is supplied, to which a sinusoidal signal 5 from the generator 10 is supplied. The reference signal of the TO generator and the measuring signal from the detector 12 are supplied to the phase detector 11. The voltage from the output of the phase detector 11 is applied to the electronic frequency tuning element of the generator 8 frequency, to the coaxial output of which the recorder t3 is connected.

The device operates as follows.

5 The acoustic emission signal is excited by an electro-acoustic transducer 4, the electrical signals of which are amplified by an amplifier 5 and detected by an amplitude detector b in order to isolate the low-frequency component of the signals. The resulting low-frequency signal is amplified by an amplifier 7, from the output of which a voltage is supplied to the electronic tuning element 3 of the natural frequency

5 of the electromagnetic oscillations of the resonator 2. For example, a varicap, the capacitance of which depends on the applied voltage, or a ferrite sample, the magnetic permeability of which varies with the magnitude of the current flowing through the winding located on it, can be used as element 3. In the absence of acoustic emission signals from the generator 8, through the modulator 9, the oscillations of the electromagnetic field are fed to the resonator 2. It is excited at the resonant frequency. In this case, there is no voltage at the output of the phase detector 11, since in-phase voltages are supplied to its inputs from the generator 10 and the detector 12. When occurring

Acoustic emission signals on varicap 3 exhibit a voltage that changes the capacitance of its pn junction and. therefore, the natural frequency of the resonator 2. As a result, the phase of the signal at the output of the detector 12 changes and the output of the phase detector 11 exhibits a voltage that changes the frequency of the generator 8, adjusting it to the new natural frequency of the resonator 2. This frequency reflects the information about the acoustic emission signal and is recorded by the recorder 13.

When the resonator 2 is operating at microwave frequencies (C H V) of the electromagnetic field (resonant frequency .fps9.4x109f-Hz), the steepness of its electronic tuning using a varicap can be (Hz / V), which ensures high sensitivity of the device and allows you to select the mode Since the Q factor of the resonators in the microwave range to tens or even hundreds of thousands of hours, the inertia of the device does not exceed tens of microseconds and, therefore, the dynamic error is measured Since the cavity resonator can be made with a given stiffness, and varicaps and ferrite samples can operate with significant vibrations, the proposed technical solution is vibration resistant and can significantly reduce the error due to vibration noise. having all the elements of the phase locked loop of the generator frequency in the shielded case of the device.

Claims (1)

SUMMARY OF THE INVENTION A device for recording acoustic emission signals, comprising an electro-acoustic transducer and a shielded housing, an amplifier arranged in series with an input connected to an electro-acoustic transducer, an amplitude detector, a detected signal amplifier and a recorder, characterized in that, in order to increase accuracy and reliability registration, the registrar is made in the form of a volume resonator of electromagnetic field oscillations with an element of electronic tuning of the natural frequency, the input of which is connected to the output of the amplifier of the detected signals,