SU1252667A1 - Method and apparatus for measuring shifts - Google Patents

Abstract

The invention relates to a measurement technique and can be used when measuring displacements. The aim of the invention is to increase the measurement accuracy by varying the frequency of the ultrasonic wave being excited in order to create a constant propagation velocity of the latter. In a device that implements a method of measuring displacements, the generator periodically excites ultrasonic waves using an excitation coil in the duct. Voltage pulses are induced in receiving coils with moving and stationary magnets. Under the influence of destabilizing factors, the delay time in the reference channel changes. A change in the carrier frequency of the emitted signal changes the velocity V of the ultrasonic waves and maintains the propagation time of ultrasound in the reference channel o / V, where a is the distance; not from the excitation coil with a permanent magnet to the receive coil with a permanent magnet, V is the speed of ultrasound propagation in the duct, constant. The carrier frequency is changed by means of a generator controlled by a Uypp nag from a time-voltage converter, at the input of which a signal from the subtractor is fed. The subtractor compares the signals from the generator of exemplary time intervals and the first amplifier-former. The pulses induced in the pickup wheel with a movable magnet, through the second controlled filter and the second booster amplifier, go to a time interval meter, which records the delay time t, X / U, where is the distance from the excitation coil with a permanent magnet to the receive coil with a movable magnet proportional to the displacement measured. 2 sec. f-ly, 1 ill. i (Lio 1 a: 1

Description

The invention relates to a measurement technique and can be used when measuring displacements.

The purpose of the invention is to improve the measurement accuracy by changing the frequency of the ultrasonic wave being excited to create a constant propagation velocity of the latter.

The drawing shows a device that implements a method for measuring displacements.

The device contains a magnetostrictive transducer 1, consisting of a chimney 2, an excitation coil 3 and two receiving coils A and 5 with stationary and movable magnets 6, 7 and 8, a generator 9 connected to the excitation coil 3, a reference channel 10 connected to the coil 4 of the reception with a fixed magnet 7, the working channel 11 connected to the coil 5 of the reception with a movable magnet 8, the generator 9 is made controlled, the support channel 10 made in the form of serially connected first controlled filter 12 connected to the coil 4 at stationary magnet 7 ma, first amplifier-maker 13, subtraction unit 14 and time-voltage converter 15 connected to generator input 9 and second input of first controlled filter 12, and generator 16 exemplary time intervals connected to second block input 14, and the second output of the generator 9 is connected to the control inputs of the generator 16 exemplary time intervals, the subtraction unit 14 and the time-voltage converter 15, the working channel 11, made in the form of serially connected second controls an inlet filter 17 connected to the reception coil 5 with a movable magnet 8, a second amplifier 18, and a time interval meter 19, the control input of which is connected to the second output of the generator 9, and the second input of the second controlled filter 17 is connected to the output of the converter 15 time voltage.

A device that implements the method of measuring displacements, works as follows.

The generator 9 periodically excites using a coil 3 excitation package of longitudinal ultrasonic waves

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As a result, directly about the magnetostriction E () effect in the chi-conductor 2. In the coils 4 and 5 of the reception, voltage pulses are induced due to the reverse magnetostriction T1} k} 1ct. In working

channel 11 time i passed

between the moment of excitation of the excitation coil 3 and the reception of the ultrasonic pulse by the reception coil 5 depends on the position X of the subconductor / s magnet 8 and the speed of sound in the acoustic cable 2. The speed of sound V in the material of the acoustic pipe 2 depends in a known manner on the temperature of the acoustic pipe 2 a, therefore, the ambient temperature. In reference channel 10

delay time

{°

between the moment

the radiation of the ultrasonic pulse by the coil 3 and the moment of reception of this wave by the coil 4 depends only on the speed of sound V, since the stationary magnet 7 and catutac 4 are set at a fixed distance a from the coil 3.

Thus, the time to is determined only by the speed of sound V and the carrier frequency t of pulsed signals,

moreover, the carrier frequency period {is chosen 10-15 times less than the duration of the pulse itself in order to achieve a sufficiently narrow spectrum of the emitted ultrasonic waves. The pulse repetition period of the generator 9 is chosen longer than the time / / V.

Under the influence of destabilizing factors, the delay time in the reference channel 10 changes. By changing the frequencies of the frequency f of the emitted signal, the velocity of the longitudinal waves V (f) is changed and they support {const. In the device, the change of the carrier frequency of the pulses is carried out by means of a generator 9 controlled by the voltage from the time-voltage converter 15. The first and second controlled filters I2 and 17 are also controlled by this voltage, which changes

their resonant tuning frequency simultaneously with the change of the carrier frequency of the generator 9.

The voltage pulses induced in the coil 4 of the reference channel are supplied

through the first controlled filter 12 to the first amplifier driver 13 and then to the input of the subtraction unit 14, to the other input of which

pulses from an If) generator exemplary time intervals. The output signal from the subtraction unit 14 is fed to the time-voltage converter 15, the voltage of which controls the carrier frequency f of the generator 9, as well as the tuning frequency of the filters 2 and 17. The pulses induced in the coil 5 go through the controlled filter 17 to the amplifier -former 18 and later on the meter 19 time intervals for recording the delay time rm, proportional to the movement of the magnet 8 (V const, if t% is kept constant).

Claims (2)

1. A method for measuring displacements, in that a magnetostrictive transducer is excited by a permanent magnet excitation oscillation coil in a acoustic duct and is received by receiving coils with fixed and movable magnets, so that, in order to improve accuracy, time is measured propagation of ultrasonic oscillations from the excitation coil to a permanent magnet pickup coil, compare the latter with an exemplary time interval, change the frequency of the ultrasonic oscillations of the cat the excitation ears until the time intervals compared are matched, and the time of the ultrasonic pulse propagation from the excitation coil to the receiving coil with a moving magnet is measured, from which the desired parameter is determined. 52f ft74 2. A DPP displacement measurement device containing a magnetostrictive transducer consisting of a chute, a power coil and 5 two receive coils with a nb movable and moving magnets, a generator connected to the excitation coil, an onopHbrfi channel connected to the receiving coil with a fixed magnet, a working channel connected to a receiving coil with a movable magnet, characterized in that, in order to increase the accuracy, the generator is controlled, the reference kanggsh consists of sequentially connected first controlled the filter connected to the receive coil with a non-plug-in magnet, the first amplifier-former, the subtractor unit, and the time-to-time converter 10 t5 20 five 0 five 0 connected to the input of the controlled generator and the second input of the first controlled filter, and a generator of sample time intervals connected to the second input of the subtractor; the second output of the controlled generator is connected to the control inputs of the generator of sample time intervals, the subtractor and time converter - voltage, the working channel is made in the form of a second controlled filter connected in series, connected to a receiving coil with a movable magnet, a second shaping amplifier, and A time inter-shaft meter, whose control input is connected to the second output of the controlled generator, and the second input of the second controlled filter is connected to the output of the time-voltage converter. Compiled by G. Ryzhakov Editor M. Vlanar Tehred M. Khodanich Proofreader M. Pojo Order 4615/43 Circulation 670 Subscription VNIIPI USSR State Committee for inventions and discoveries N3035, Moscow, Zh-35, Raushsk nab. A / 5 Free-printing enterprise, Uzhgorod, Projecto st., 4