RU2381498C1 - Calibration method for acoustic emission detectors and device for implementation thereof - Google Patents

Abstract

FIELD: measuring technology.

SUBSTANCE: application: for calibration of acoustic emission detectors. An input of the calibrated detector, a test acoustic signal is reproduced at various frequencies with measuring a response of the detector at various frequencies that is followed with computer processing the measurement results. The test acoustic signal is reproduced in the input of the calibrated detector at various frequencies by dropping from the fixed height on a sensitive element of the detector of size-calibrated sand particles. The dropping of the size-calibrated sand particles on the sensitive element of the detector is ensured consistently by separate particles at the interval that in 2-3 times exceeds the maximum pre-measured response of the calibrated detector at the set frequency.

EFFECT: enabled reproduction of a precise test acoustic signal directly actuating the sensitive element of the calibrated detector without intermediate acoustic contacts.

5 cl, 4 dwg

Description

The invention relates to the field of measurement technology and can be used to calibrate acoustic emission sensors used in the operation of gas wells.

A known method for a similar purpose, implemented in a simulator of acoustic emission signals, which consists in reproducing at the input of a calibrated acoustic emission sensor (DAE) a test signal using a special simulator of acoustic emission signals.

Using a fastener, the simulator is mounted directly on the product being monitored, being a calibrating unit for calibrating the measuring paths (AS CCC No. 1363057, class G01 No. 29/04, 1987).

A device for a similar purpose is known, including a waveguide in the form of an elastic element with a linear law of deformation and concentrators, as well as a fragile coating of regenerated material (AS USSR No. 1363057, G01N 29/04, 1987).

A disadvantage of the known analogues of the method and device is the low accuracy of the DAE calibration, associated with the randomness of the test signal reproduction.

A known method of calibrating the DAE, which consists in reproducing at the input of the calibrated sensor at different frequencies a test acoustic signal supplied to the sensor via an acoustic spacer, and measuring the response of the sensor to test signals at different frequencies, followed by processing the measurement results on a computer (RF Patent No. 2321849, CL G01N 29/04, G01N 29/30, 2008).

This method is adopted as a prototype.

In the prototype, the amplitude of the test signal is measured using an interferometer.

A device for calibrating a DAE is known, comprising a control unit connected to a test signal master, a meter for the amplitude of the response of the calibrated sensor to a test signal at various frequencies, and a processing unit including an amplifier connected via an analog-to-digital converter (ADC) board to a computer with connected to it with a monitor and printer (RF Patent No. 2321849, class G01N 29/04, G01N 29/30, 2008).

This device is taken as a prototype device for calibrating the DAE.

The disadvantage of the prototype method and device is the low accuracy of the calibration. This is due, in the case of the method, to the randomness of the reproduced acoustic signal, and in the case of the device, to the absence of a direct acoustic signal at the input of the DAE sensitive element.

The technical result obtained from the introduction of the method and device is to increase the accuracy of the DAE calibration by reproducing a distinct test acoustic signal that directly affects the sensitive element of the calibrated sensor without intermediate acoustic contacts.

This technical result in terms of the method is achieved due to the fact that in the known DAE calibration method, which consists in reproducing at the input of the calibrated sensor at different frequencies a test acoustic signal and measuring the response to test signals at different frequencies during subsequent processing of the measurement results on a computer, playback on the input of the calibrated sensor at various frequencies of the test acoustic signal is carried out by dropping from a fixed height to the sensitive element of a sensor of size-calibrated sand particles, moreover, dropping size-calibrated sand particles on a sensor element is carried out sequentially by individual particles with a period of their falling on the sensor element of the sensor, not less than 2 ÷ 3 times the maximum value of the measured response time of the calibrated sensor at a given frequency.

In terms of the device, this technical result is achieved due to the fact that in the known device for calibrating the DAE containing a control unit connected to a test acoustic signal generator, a meter for the amplitude of the response of the calibrated sensor to the test signal at various frequencies and a processing unit including an amplifier, connected through an ADC board to a computer with a monitor and printer connected to it, the test acoustic signal generator is made in the form of a sand accumulator with an opening at the bottom, controlled by a metering device calibrated by size of sand particles located at a fixed height above the sensitive element of the calibrated sensor, while the controlled metering device is made in the form of mechanically connected inclined grooves and orthogonally oriented vibrators, with a sand accumulator with an opening at the bottom and a vibrator operating in horizontal plane across the gutter, and from the bottom - a vibrator operating in a vertical plane, and the controlled inputs of the vibrators are connected to the output of the control unit I am.

Moreover, the angle of inclination of the gutter of the dispenser to the horizon is (5 ÷ 15) °.

Calibrated DAE mounted on the bellows.

A vertical guide funnel is mounted on top of the DAE sensor.

The invention is illustrated by drawings.

On figa, b presents diagrams explaining the essence of the method, figure 2 is a diagram of a device for implementing the method, figure 3 is a diagram explaining the essence of the method and operation of the device.

The duration of a response to an individual impact depends on the choice of frequency in a wide range of the output signal from the calibrated DAE (see Fig. 1a, frequencies A, B, C), and the coincidence of the previous response to the impact with the leading edge of the subsequent impact distorts the amplitude distribution of the recorded responses (see Fig.1b, blows under numbers 2, 3 and 4).

The device (figure 2) contains a control unit 1 connected to the setpoint of the test acoustic signal, made in the form of a drive 2 of sand located at a fixed height. A hole is made at the bottom of the drive 2. The setter also contains a dosing device of calibrated size sand particles made in the form of an inclined trough 3 and two orthogonally oriented vibrators 4 and 5 mechanically connected to it. A sand accumulator 2 and a vibrator 4 are connected to the upper part of the batcher, the vibrating rod of which runs across the horizontal trough 3 the plane. With the bottom of the dispenser docked vibrator 5, working in a vertical plane.

The controlled inputs of the vibrators 4 and 5 are connected to the output of the control unit.

The calibrated sensor is indicated at 6. The output of the sensor 6 is connected through an amplifier and an ADC to a computer performing statistical processing of the amplitude of responses to particle impacts connected to a monitor and a printer (Blocks of secondary equipment of sensor 6 are not shown in FIG. 2).

The angle α of inclination of the chute 3 of the dispenser to the horizon is (5 ÷ 15) ° and together with the vibrator 4 they determine the flow rate of sand. The vibrator 5 provides uniform distribution of particles in the trough. The sensor 6 can be mounted on a bellows (not shown in figure 2) for the purpose of acoustic isolation.

A guide funnel 7 can be installed on top of the sensor element 6, adjusting the flow of particles to the surface of the sensor element.

The calibration method of the DAE is implemented as follows.

Using the test acoustic signal generator at the input of the calibrated sensor, a sequence of acoustic signals is reproduced - responses to particle impacts at various frequencies. In this case, from the accumulator 2 sand particles calibrated by size to the inclined trough 3, sand particles arrive. The speed of movement of sand particles along the trough 3 is determined by the inclination of the trough, and the uniformity of the particles and flow rate by the frequency and amplitude of vibration of the trench 3.

At the top of the inclined groove 3 vibrate using a vibrator 4 in a horizontal plane across the groove. This allows you to set and stabilize the flow rate of particles in the trench. At the bottom of the inclined groove 3 vibrates in a vertical plane, dividing the flow of sand into separate particles. The uniformity of the supply of particles in the adjustment funnel 7 provides a vibrator 5.

As experiments have shown, the optimal material for the manufacture of the trough 3 is stainless foil (0.1 ÷ 0.2) mm thick, the optimum angle of inclination to the horizon is the angle (5 ÷ 15) ° C, and the optimal frequency range under these conditions is ( 100 ÷ 1000) Hz, if the length of the gutter does not exceed (10 ÷ 15) cm.

To eliminate the influence of external fixing devices, the sensor 6 is placed on a bellows, acting as an acoustic isolation (not shown in figure 2).

Since all DAEs undergo metrological certification, including graduation, before commissioning, the duration of the response of the calibrated sensor 6 to the test signal is approximately known. Using the described device, it is ensured that the period following the fall of individual particles of calibrated sand on the DSP-AKE sensitive element exceeds at least 2–3 times the maximum response time of the sensor.

This makes it possible to obtain single impacts of particles on the sensor element of the sensor 6 during calibration and to eliminate distortions of the Gaussian distribution of the response amplitudes specified by the height of incidence of the calibrated particles. In this case, the average value of the amplitude of responses of recorded shocks, as well as the position of the maximum in the distribution of amplitudes on the intensity scale, does not depend on the flow rate and is determined only by the height of the particles (see Fig. 3).

The acoustic response of the impacts of sand particles is converted by the sensor 6 into an alternating voltage, which, after the amplifier, is supplied to the fast ADC board (not shown in FIG. 2).

Then, using a computer in real time, a fast Fourier transform, digital recording of the calibration signal at given frequencies, an analysis of the statistics of the amplitudes of the responses of the distribution of responses by amplitude with the determination of the average value of the recorded beats and the position of the maximum in their distribution on the intensity scale are performed. In this case, the difference between the average value of the amplitude of the recorded shocks and the position of their maximum in the distribution on the intensity scale (i.e., the asymmetry of the distribution itself) allows you to control the degree of uniformity of the calibrated particles in size. The larger the difference, the less uniform the calibrated sand.

Figure 3 shows the distribution of the intensity of the responses of the DAE during the calibration of individual calibrated sand particles. Curve 1 - real distribution; 2 - smoothed distribution function; 3 - the position of the maximum distribution on the intensity scale; 4 - position of the average value of responses for the calibration period).

Clearly separated in time test acoustic signals supplied to the input of the calibrated sensor, allow to increase the accuracy of calibration, achieving the set technical result.

The method and device are introduced into the production cycle of acoustic sensors - signaling devices for sand and droplet moisture in the gas stream in pipelines at underground gas storages and at gas production facilities of Gazprom.

Claims (5)

1. A method of calibrating acoustic emission sensors, which consists in reproducing at the input of the calibrated sensor at different frequencies a test acoustic signal and measuring the response of the sensor to test signals at different frequencies during subsequent processing of the measurement results on a computer, characterized in that it reproduces at the input of the calibrated sensor at various frequencies of the test acoustic signal is carried out by dropping from a fixed height on the sensor element calibrated by size sand particles, moreover, the calibration of sand-sized particles of sand onto the sensor element is carried out sequentially by individual particles with a period 2-3 times the maximum value of the previously measured response time of the calibrated sensor at a given frequency. 2. A device for calibrating acoustic emission sensors, comprising a control unit connected to a test acoustic signal generator, a meter for the amplitude of the response of the calibrated sensor to the test signal at various frequencies, and a processing unit including an amplifier connected via an analog-to-digital converter board to a computer with a monitor and printer connected to it, characterized in that the setter of the test acoustic signal is made in the form of a sand accumulator with an opening at the bottom, controlled by a dispenser calibrated by the size of sand particles located at a fixed height above the sensitive element of the calibrated sensor, while the controlled dispenser is made in the form of mechanically connected inclined trough and orthogonally oriented vibrators, and a sand accumulator with an opening at the bottom and a vibrator operating in the horizontal plane are connected to the upper part of the trough across the gutter, and from the bottom - a vibrator operating in a vertical plane, and the controlled inputs of the vibrators are connected to the output of the control unit. 3. The device according to claim 2, characterized in that the angle of inclination of the gutter of the dispenser to the horizon is (5 ÷ 15) ° C. 4. The device according to claim 2, characterized in that the calibrated acoustic sensor is mounted on a bellows. 5. The device according to claim 2, characterized in that a funnel is vertically mounted on top of the sensor element.

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