RU2117914C1 - Method measuring linear translations - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: mobile reading element is set at nearest distance from immobile excitation element only once before measurement of propagation time of ultrasonic wave from excitation zone to reading zone and duration of pulse of ultrasonic wave received by reading element is measured. Duration of pulse is measured each time before measurement of translation. Value of pulse measured after translation of mobile element together with controlled object to measured distance is subtracted from value of duration of pulse measured during location of mobile element directly near immobile excitation element. Current of excitation element determined value of this difference. Resulting time interval t_x , proportional to measured translation is found from expression t_x = (t₁+ t₂)/2,, where t₁ and t₂ are moments of operation of threshold device receiving pulse of ultrasonic wave correspondingly by leading and trailing edges of this pulse. EFFECT: increased measurement accuracy in magnetostriction converters of translations. 2 cl, 2 dwg

Description

 The invention relates to measuring technique and can be used to improve accuracy in magnetostrictive displacement transducers.

 A known method of measuring displacements, based on measuring the transit time of an ultrasonic wave through a waveguide of magnetostrictive material from the excitation zone to the read zone [1].

 The disadvantage of this method is the low accuracy due to the attenuation of the ultrasonic wave in the waveguide.

 Closest to the invention in technical essence is a method of measuring linear displacements, implemented in a linear displacement transducer [2], in which the magnitude of the current of the excitation element is determined by the magnitude of the amplitude of the pulse of the ultrasonic wave received by the read element.

 However, the implementation of this method leads to a decrease in noise immunity due to the necessity of measuring the amplitude of the ultrasonic wave pulse received by the sensing element, which causes a decrease in the measurement accuracy.

 The objective of the invention is to improve the accuracy.

The problem is solved in that in the method of measuring linear displacements using an ultrasonic transducer, which consists in measuring the propagation time of an ultrasonic wave from a stationary excitation element to a movable read element connected to a controlled object, the value of the linear displacement before the measurement cycle only once during the entire operation period, the movable reading element is installed at the closest distance to the stationary element wait and measure the pulse duration of the ultrasonic wave received by the reading element, and each time before measuring the pulse duration of the ultrasonic wave is measured, from the value of the pulse duration of the ultrasonic wave measured when the movable reading element is located directly near the stationary excitation element, the value of the pulse duration of the ultrasonic wave measured after how the movable reading element moved with the controlled object to the measured distance thaw, and the current of the excitation element depends on this difference. In addition, each time before the measurement cycle, a threshold voltage is set in the receiving part, k times the noise voltage, where k is the coefficient determined by the noise immunity requirements, and the resulting time interval t _x proportional to the measured displacement is determined from the expression: t _x = (t ₁ + t ₂ ) / 2, where t ₁ and t ₂ (Fig. 2) are the moments of operation of the threshold device when receiving an ultrasonic wave pulse, respectively, on the leading and trailing edges of this pulse.

 The invention is illustrated by drawings. In FIG. 1 shows a block diagram of a device for implementing this method of measuring linear displacements, FIG. 2 is an image of an ultrasonic wave pulse at the input of a threshold device.

 A device for implementing the method includes: sound duct 1 of magnetostrictive material; a stationary excitation element 2 with a magnetization element 3 a movable reading element 4, rigidly connected with the controlled object, with a magnetization element 5, acoustic dampers 6 located at the ends of the sound duct 1; an amplifier 7 of excitation pulses connected to the stationary excitation element 2, the input of which is connected to the output of the first digital-to-analog converter 8, to which a code from port A of the programmable digital control unit 10 is supplied through an n-bit bus (where n is the bit capacity of the first DAC); a synchronization unit 9 associated with a programmable digital signal control unit 10: ready ("Ready"), settings ("Set 1" and "Set 2"), measurement resolution ("Measure"); an amplifier 12 of read pulses, to the input of which a movable reading element 4 is connected, and to the output, the second input of the comparator 13, the first input of which receives a signal from the output of the second digital-to-analog converter 11, whose inputs are connected via a q-bit bus (where q is the bit depth of the second DAC) to port B of the programmable digital control unit 10; a pulse width measuring circuit 14, from the output of which the signal is transmitted over the l-bit bus (where l is the bit length of the received signal duration code) to port C of the programmable digital control unit 10; a circuit 15 for measuring the propagation time of an ultrasonic wave, which outputs to the port D of the programmable digital control unit 10 an m-bit time interval code proportional to the movement, and to which a signal is received from the programmable digital control unit 10 and a signal from the comparator 13, the same signal is also transmitted to a programmable digital control unit 10 and to a pulse width measuring circuit 14; an indication unit 16, the input of which is connected by an m-bit bus to port E of the programmable digital control unit 10.

 An example of a specific implementation of the method.

 Before starting the linear displacement measurement cycle, two installation operations are performed.

First, the operator using the synchronization unit 9 generates a “Set 1” signal, which is transmitted to the programmable digital control unit 10, which, through the second digital-to-analog converter 11, sets some voltage, obviously higher than the noise voltage, to the first input of the comparator 13, there will be voltage at the second input of the comparator 13 equal to the noise voltage, because during the operation "Installation 1" the electric signal to the stationary element 2 of the excitation is not received. Programmable digital control unit 10 through the second digital-to-analog converter 11 reduces the voltage at the first input of the balanced comparator 13 until the voltages at both inputs of the comparator 13 become equal (as evidenced by the appearance of a signal of a logical unit at the output of the comparator 13). After that, the programmable digital control unit 10, using the second digital-to-analog converter 11, supplies a voltage equal to k x U _noise to the first input of the comparator 13, where k is the coefficient determined by the noise immunity requirements and maintains this voltage until the next signal “Set 1 "(this voltage will be the threshold for the receiving part of the device); after the operation "Installation 1" is completed, the programmable digital control unit 10 supplies the ready signal "Ready" to the synchronization unit 9.

 The operation "Installation 1" is repeated each time before the measurement cycle, and after turning on the device, the operation "Installation 1" is followed by the operation "Installation 2", followed by the measurement cycle.

 This is followed by the operation "Installation 2" after the movable reading element 4 is installed at the closest distance to the stationary excitation element 2, the operator using the synchronization unit 9 generates a signal "Set 2", according to which the programmable digital control unit 10 using the first digital-to-analog Converter 8 generates a signal of maximum amplitude and feeds this signal to the input of an amplifier 7 of the excitation pulses, which amplifies this electrical signal and supplies it to the input of the stationary element 2 of the excitation. Further, due to direct magnetostrictive conversion, an ultrasonic wave is excited in the sound pipe 1, which propagates on both sides of the stationary excitation element 2. Propagating to the left, the ultrasonic wave reaches the acoustic damper 6, on which it dissipates its energy. Propagating to the right through the sound pipe 1 relative to the stationary excitation element 2, the ultrasonic wave reaches first the movable reading element 4, and then the acoustic damper 6, on which it dissipates its energy. Due to the inverse magnetomechanical transformation in the movable reading element 4, when it is reached by an ultrasonic wave, an electric pulse is induced, which, after amplification in the amplifier 12 of the read pulses, enters the second input of the comparator 13, the signal from which the pulse width measuring circuit 14 measures the pulse duration an ultrasonic wave received by the reading element 4. Measured and converted into a digital code by the pulse width measuring circuit 14, the pulse width is recorded in the memory of the programmable digital control unit 10.

 Operation "Installation 2" is performed once during the entire operation of the device — after turning on the device and performing the operation "Installation 1" with the operation "Installation 1" and in the further operation of the device, the code obtained as a result of the operation "Installation 2" is used as a reference.

 After the operation "Installation 2" is completed, the programmable digital control unit 10 sets the ready signal "Ready." to block 9 synchronization. In response, the operator, through the synchronization unit 9, sets the measurement enable signal “Measurement” on the programmable digital control unit 10, according to which the measurement cycle begins, consisting of two operations: the adjustment operation and the measurement operation itself.

 The tuning operation consists in maintaining a constant pulse duration of the ultrasonic wave received by the reading element 4 by changing the amplitude of the emitted signal, i.e. the same actions are performed as in the operation "Installation 2", but with some differences: firstly, the movable reading element 4 has already moved along with the controlled object by the measured distance, and secondly, the pulse duration of the ultrasonic wave received by element 4 readout, measured and converted into a code by the pulse width measuring circuit 14, enters the programmable digital control unit 10 and is subtracted from the model code obtained as a result of the operation "Installation 2", and the code obtained as a result After this subtraction, it arrives at the first digital-to-analog converter 8, which at the output generates an analog signal with an amplitude proportional to the code at its inputs. Further, this signal through the amplifier 7 of the excitation pulses is supplied to the stationary element 2 of the excitation. Simultaneously with the code at the inputs of the first digital-to-analog converter 8, the programmable digital control unit 10 generates a signal that triggers the ultrasonic wave propagation time measurement circuit 15. In the movable reading element 4, the ultrasonic wave pulse is converted into an electric signal, which is fed to the second input of the comparator 13. A digital pulse from the output of the comparator 13 is fed to the ultrasonic wave propagation time measurement circuit 15 and serves as a stop signal for this circuit.

Simultaneously with measuring by the circuit 15 measuring the propagation time of the ultrasonic wave of time t _x (Fig. 2), the propagation of the ultrasonic wave from the excitation element 2 to the reading element 4 and converting it into a digital code N _t1 , the measuring circuit 14 measures the pulse duration of the duration of the received pulse of the ultrasonic wave Δt (Fig. 2) and converting it into a digital code N _Δt . The obtained digital codes N _t1 and N _Δt are received in a programmable digital control unit 10, where the digital code of the interval t _{2 is} calculated (Fig. 2): N _t1 + N _Δt , after which the resulting code of the propagation time of the ultrasonic wave from the excitation element 2 to reading element 4: N _tx = (N _t1 + N _t2 ) / 2 and issuing it to the display unit 16. The measurement cycle is completed.

 Due to this sequence of measurement and calculation operations, the proposed method can significantly increase the accuracy of ultrasonic transducers, firstly, by reducing the error in measuring the propagation time of an ultrasonic wave by 1.41 times, and secondly, by compensating for the error caused by the attenuation of pulses of the ultrasonic wave in the sound pipe.

 Compensation of this error is achieved by the fact that the current of the excitation element is determined by the difference between the exemplary value of the pulse duration of the ultrasonic wave received by the read element and the operating value of the pulse duration of the ultrasonic wave received by the read element, measured respectively when the movable read element is in close proximity to the stationary excitation element and when the movable reading element has already moved together with the controlled object my distance. Under such conditions, measuring the duration of the pulses of the ultrasonic wave received by the reading element, the value of the difference of these durations can be used to judge the change in the duration of the received pulses of the ultrasonic wave depending on the position of the moving reading element relative to the stationary excitation element 2, i.e. the magnitude of the attenuation of the pulses of the ultrasonic wave depending on the distance traveled by these pulses from the excitation zone to the read zone. That is, ultimately, the current of the excitation element depends on the attenuation of the pulses of the ultrasonic wave in the sound duct.

Sources of information
1. Domrachev V.G., Matveevsky V.R., Smirnov Yu.S. Circuitry of Digital Displacement Transducers: A Reference Guide. - M .: Energoatomizdat, 1987.

 2. Copyright certificate of the USSR N 1394033, published. 05/07/88 Bul. N 17.

Claims (3)

 1. A method of measuring linear displacements using an ultrasonic transducer, which consists in measuring the propagation time of an ultrasonic wave from a stationary excitation element to a movable reading element connected to a controlled object, the value of the linear displacement is judged by the value of this time, characterized in that before by measuring the propagation time of the ultrasonic wave from the excitation zone to the read zone, only once during the entire operation time, a movable read element is installed at the closest distance to the stationary excitation element and measure the pulse duration of the ultrasonic wave received by the reading element, and each time before measuring the pulse duration of the ultrasonic wave is measured, from the value of the pulse duration of the ultrasonic wave measured when the moving reading element is located directly near the stationary excitation element, subtract the value of the pulse duration of the ultrasonic wave, measured after the movable reading element p remestilsya together with the controlled object on the measured distance and a value of this difference determines the current of the drive element.  2. The method according to claim 1, characterized in that before each measurement cycle a threshold voltage is set in the receiving part, k times greater than the noise voltage, where k is the coefficient determined by the noise immunity requirements. 3. The method according to claim 1, characterized in that the resulting time interval t _x proportional to the measured movement is determined from the expression
t _x = (t ₁ + t ₂ ) / 2,
where t ₁ and t ₂ are the moments of operation of the threshold device when receiving an ultrasonic pulse, respectively, on the leading and trailing edges of this pulse.

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