SU746279A1 - Apparatus for measuring velocity of ultrasound - Google Patents

Description

(54) DEVICE FOR MEASURING THE SPEED OF ULTRASOUND The invention relates to the field of ultrasound technology and can be used to study the physicochemical properties of various materials in a solid or liquid state, namely, to determine the concentration of chemical components of density, specific gravity, viscosity flow. substances under investigation, as an analyzer of temperature characteristics and a parameter sensor for various technological processes, for measuring geometrical dimensions, elastic constants tel. The invention will find its most effective use in measuring residual stresses in metals and metal structures without destroying them, for example, after welding in cases where the field of residual stresses has two axial character. A device is known for measuring the velocity of ultrasound in solids, based on the frequency-pulse method for determining the time of propagation of an ultrasonic wave. In a current device, it is used in an autocirculation Tsip, which implies that the ultrasonic pulse generator is restarted by a pulse that passes through the medium 1 being measured. However, with the auto-circulating frequency established and with sufficient stability, this device determines only the relative change in the ultrasound transmission speed measurement time when external disturbances are applied to the object under study. Also known is a device for measuring the speed of ultrasound in seawater, built on the principle of forced pulsed frequency-phase synchronization, using the identity of the speed of ultrasound, the time required for the ultrasound pulse and its reflection to travel along a strictly defined path length 2. Such a device is suitable for measuring ultrasound speeds in solids, since the measuring device can only be filled with liquid. Setting the optimal synchronization mode is carried out

tel indicator, which leads to a large measurement error.

The closest in technical essence to the proposed invention is a device for measuring the speed of ultrasound, comprising a generator connected to an ultrasonic transducer, a mechanism connected with a controlled medium and through an electronic key with an amplifier, a unit. autorun, linking reHejpatop with an amplifier, the output of which is loaded on the detector connected to the recalculated unit 3.. ; . .

A disadvantage of this device is the presence of a constant error in determining the speed of ultrasound transmission associated with the uncertain WcTcTbio amplitude of the detected pulses of recalculation into it.

The invention of the invention is an increase in measurement accuracy.

The goal is achieved by the fact that the device is equipped with an additional amplifier, blocks of independent SELECT, automatic stabilization of the amplitude of the half-wave restart and constant video control, the first input of the Amplifier is connected with the electronic key stroke, its second input is connected with the output of the automatic-stabilization half-wave amplitude of the restart and the output of this amplifier is loaded to the first input of the independent selection unit, the second input of which is connected to the first output of the recalculating unit, the first output of the independent se unit the lecture is loaded parallel to the input of the generator and the automatic stabilization unit for the amplitude of the half-wave restart, and its second output is connected to the first input of the constant video-control unit, the second in the course of which is from 5 in. N.V. the output of the counting unit, which has simultaneous feedback through the delay line with its own input.

FIG. 1 is a block diagram of the device; in fig. 2 - diagrams of electrical processes.

The device contains a generator 1, an ultrasonic transducer 2 mechanically connected to a controlled medium 3, an electronic switch 4, an amplifier 5, a detector 6, a transducer unit 7 having feedback through the link 8 with its own input, and a unit Autostart 9, coupling amplifier 5 with generator 1 The device also contains an additional amplifier 10, an independent selection unit 11, a block 12 Automatic stabilizing ayplaytuPaPluohoa restarting unit 13 constant video control.

The device is equipped with a digital frequency counter included in any point 1 of the closed loop and the second loop,

746279

preferably to generator D, or to Perez-even block 7 (not shown in the diagram).

The operation of the device is taken away by diagrams of electrical processes (Fig. The moment when the pulses of ultrasonic vibrations do not pass through the controlled medium is taken as the initial state.

1 Without receiving the AGC signal from block 5 - the first amplifier of radio pulses, the autorun unit 9 outputs a pulse with its own repetition period Tc (Fig. 2, a) to the second input of the generator 1, starting it (Fig. 2, c).

From the output of the key 4 to the input of the amplifiers 5 and 10 synchronously enters a series of small values of radio pulses decreasing in amplitude with a filling frequency equal to b15. The actual frequency of the ultrasonic transducer 2 (Fig. 2c). According to diagram c, it is necessary to make a conditional assumption consisting in a honey beetle. At a certain number of reflections, for example, the fourth, ultrasonic signal. The device will switch to the autocirculation mode, and the further character of the diagram shown will be disturbed. For simplicity of explanation of the time intervals, the diagram in Fig. 2 remains unchanged, assuming that, after the nth number, it is quite similar to, reflecting the actual picture of steady state autocirculation.

A continuous series of amplified radio pulses from the first output of the amplifier 5 is fed to the input of detector b, the output of which is converted to. continuous video pulse. Regardless of the state in which the counting unit 7 / is at the moment it arrives at its first input of the video pulse from the amplitude of the leading edge above the trigger threshold, a voltage select (Fig. 2) appears at its output, part of which is its second output through the delay line 8 is returned to your own second input, Reset, transfer of block 7 to the initial state of the account before. the arrival of the next M-th video impulse in a repeating number of reflections (Fig. 2, d). Thus, the initial surge voltage at the output of block 7 is transformed into a distinct video pulse whose duration is equal to the delay time of the delay 8, and the duration of its front and fall, depending only on the particular properties of block 7, can be reduced to dock and more below the quarter wavelength of ultrasonic vibrations.,

From a comparison of the cud diagrams in FIG. 2 shows that all countable

the impulse (Fig. 2 t /) / 7th number is located opposite (coincides in time) of that wave in the radio pulse

W -th number (Fig. 2, c), which, after passing an amplitude detector, causes the start of block 7.. five

In the proposed device, this phenomenon is applied. But for using the rectangular video pulse of the count

(Fig. 2, o /) as the gateway for the independent selection of that wave of the pa-IQ dioopulse that causes it, respectively (Fig. 2, c), C this. In order to achieve this, the length of the delay time of line 8 is set equal to the period Tu of ultrasonic vibrations. . converter 2,

Since the AGC system of amplifier 5, which establishes optimal conditions for the autocirculation mode, cannot be changed, a second amplifier 10, intended only for independent selection, is introduced into the proposed device

From the output of amplifier 10, an amplified radio pulse series, absolutely identical to the number of radio pulses at the output of amplifier 5 (Fig. 2, c), is sent 25 to the first input of the independent selection unit 11, to the second input of which from the output of the conversion block 7 comes a rectangular video pulse Lth number of the account set by the switch 30 nj. as a result of the implementation of a logical combination, the input series of radio pulses at the intermediate point of block 11 in full time correspondence lose one-half-half-periods except the half-period which, when the radio pulse of the pth omer is filled, enters the selection gate (Fig. 2 , e). After the cutoff half-periods are opposite. dir polarity (fig. 2, e they are shown as negative) at the output of block 11 will pass only selectable half-wave of the 1st reflection, having first amplitude (fig. 2, e) /. equal to the amplitude UQ in a de radio pulse arriving at the first input of block 11 (Fig. 2, s) from amplifier 10. The selected half-wave from the first output of block 11 as a restart pulse is fed to the first input 0 of generator 1, restarting it, i.e., the operation of the device goes into the autocirculation mode.

The generator 1, as a whole electronic device, has its own trigger threshold (see diagram / Fig. 2.1L7). In the same diagram showing a wider time process at the output of block 11 (Fig. 2 e), 60 can be seen as depending on the amplitude of the selected half-wave, however, Zit is the start time of the restart {inaccuracy .4 /) on the trigger threshold of the block 1.65

J

To eliminate errors

The proposed device introduced automatic stabilization of amplitude of the half-wave restart to 12 any constant value, for example st (diagram / in fig. 2). As a result of the amplitude stabilization at the total time T., the delay of the pulse passing through the entire ring of auto-Circulation, regardless of the type of measurement, a constant HG addition will be introduced (Fig. 2, /), not affecting the ratios of the measured autocirculation frequencies .P .

The amplitude stabilization unit 12 operates as follows. If the amplitude of the selected half-wave is equal (Fig. 2 f), block 12, after analyzing its value, generates a signal arriving at a separate input of amplifier 10 and changing its gain factor so that the amplitude of the half-wave selected for restart becomes equal to st (FIG. 2, /). Thus, the introduction of blocks 10, 18 and 12 eliminates the constant error in the measurements.

To eliminate the discrete uncertainty in the numerical value of the measured frequency F, associated with the uncertainty of the half-wave number of a radio pulse falling into the selection video pulse, a block 13 is entered into the proposed device - a block of continuous video monitoring. As soon as the recalculation unit issues the front of the video pulse of the nd number (Fig. 2, c / part of this pulse triggers the oscilloscope X (block 12) (Fig. 2, rf), and the vertical amplifier Y is given an electrical signal to realize the logical process of the radio pulse numbers with a video pulse of the i-th number at the intermediate point of block 11 (Fig. 2, e). On the oscilloscope screen, after a delay time z.o, a graphic image of the selection picture appears, which can be used to determine with confidence the half-wave count of the radio pulse led restart the generator 1. In the diagram of FIG. 2 oscilloscope screen shows that the number is equal to one half-cycle is restarted.

Claims (3)

If the envelope of the first selected half-wave of reflection b in the amplitude detector b is below the trigger threshold of counting unit 7, then the moment of occurrence of the selection video pulse will shift in time by the period of ultrasonic oscillations T, while the graphic image of the selection pattern on the oscilloscope screen of unit 13 will change in such a way that it will be easy to see that the number of the half-wave selected for restarting 17 equals two, etc. If, due to external circumstances, it is required to recalculate the measured frequency Tc from the Luwolna by half-wave (for example, to keep the ratios of measured frequencies on the laboratory sample and object, when the oscilloscope screen of the block 13 detects the offset of the selected half-wave number), such recalculation is made according to the formula G - (GSH, Fn ,, ytr, F ««, where O7 is the frequency of autocirculation on the 1st number of the reflection and on the Lth number there are half waves, HZ; Tu is the period of the own ultrasound of the oscillations of the transducer used, seconds in the case of In the autostart mode, the AGC signal from the amplifier 5 does not come in. The block 9 sends a pulse to the second input of the generator 1, and the auto-circulation process is restored automatically. In general, the speed of the ultrasound passing through the medium being measured is according to the formula / - -ft, (2) - J S.Tg / m / sen /):.,, where ff is the frequency of auto-circulation measured on the i-th reflection number, 1 second; - thickness of the investigated in -...,. ,, substances, m; , - recalculation number (X /.:. (O is the total delay time of the electric pulse passing through all functional blocks except the substance under study (sec); / 7 - the total time of the Electric pulse passing through the closed auto-circulation ring (T; 7 51), - | ± 1 Usually 7;, and the formula (2) takes on its final form (n / s). (3) in cases where the ratio “-” cannot be neglected, the speed of ultrasound propagation through the medium under study is determined by the formula (m / ce), (4) p vj-f where J is the frequency of auto-circulation, measured respectively and n + 1-OM reflection device (set by switch). Invention device for measuring the cosmic ultrasound ultrasound comprising a generator connected to an ultrasonic transducer mechanically connected to the controlled medium and through an electronic key with an amplifier, an autorun unit connecting the generator with an amplifier whose output immersed in a detector connected to a scaler, in order to improve measurement accuracy, the device is equipped with an additional amplifier, independent villages the automatic amplitude stabilization of the half-wave restart and constant video control, the first input of the amplifier is connected to the output of the electronic key, the second one (The input is connected to the output of the automatic stabilization unit of the amplitude of the half-wave restart, and the output of this amplifier is loaded to the first input of the independent selection unit, the second input of which is connected with the first output of the conversion unit, the first output of the independent selection unit is loaded in parallel to the inputs of the generator and the automatic amplitude stabilization unit by uvolny reset, and its second output coupled to a first input DC video control, the second input of which is coupled to the second output) m scaler unit having simultaneous feedback through the delay line with its input the same. Sources of information taken into account in the examination 1.R. Z. Forgacs, Improvement in the sing-around Technique, the Journal of the Alaestical Society of America, 32,; 12, 1960, p. 39 2.N. D. Wilson, D. D. Taylor, Sound velocity measurement in liquids, Electronics, 1960, v. 33, 37, p.69. 3. The copyright certificate 423377, cl. G 01 H 5/00, 1974 (prototype). //OH at P Фа1.1 i Tav S iOtt TFT Ti-84, HMf P L / jiA ,with- . . one " I " J Hf