SU1084595A1 - Device for measuring longitudinal deformation - Google Patents

Abstract

DEVICE FOR MEASURING LONG-TERM DEFORMATIONS, containing si .5.jl "iiif: .i4. A measuring circuit with a strain gauge and a pulsed power source are connected in series, characterized in that, in order to improve the measurement accuracy of pulse deformations, it is equipped with first and second strain sensors located on the measurement object on both sides of the measuring cxeMii, connected to them by two selectors and connected to their outputs by the USh circuit, the output of which is: connected to the triggering input of the pulsed power source.

Description

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 The invention relates to a measurement technique and can be used in measuring pulse deformations in rods. A device for measuring strain is known, comprising a measuring circuit with strain gauges placed on the test object and a constant voltage source for supplying said circuit 1. The disadvantage of this device is low sensitivity, as well as a change in the conversion coefficient due to heated current transducers. The current flowing through them. Such a device allows the use of high operating currents, providing high sensitivity and low power dissipation 2}. However, it has low accuracy in measuring dynamic deformations (e.g., caused by a shock), since pulsed power in the case of dynamic deformations will cause severe distortions due to the loss of a significant portion of information at the time of no power. The purpose of the invention is to improve accuracy. The goal is achieved by the fact that a device for measuring continuous deformations, containing successively connected measuring circuit with strain gauges and a source of pulse power, is equipped with first and second strain gauges located on the object of measurement on both sides of the measuring circuit, connected to them by two selectors and connected to their outputs by an OR circuit, the output of which is connected to the trigger input of the source of pulsed power. The drawing shows the block diagram of the device. A: The device contains a measuring circuit 1 with strain gauge located on the object 2 of measurement, the first 3 and second 4 deformation sensors located on both sides of the measuring circuit 1 on the object 2 of measurement, the outputs of which are connected to selectors 5 and 6, respectively The outputs of which are connected to the inputs of the OR circuit 7, and its output is connected to the triggering input of the source 8 of the pulsed power supply, connected in series with the measuring circuit 1 with strain gauges. The device works as follows. During dynamic loading of one of the ends of the measurement object 2 (for example, striking it on it), the resulting strain pulse propagates in the direction of the opposite end. The speed of propagation is equal to the speed of sound in the material of the measurement object 2. The deformation pulse, having reached the first deformation sensor 3, excites an electrical signal in it. As sensors, you can use piezoelectric elements. An electrical signal from the output of the deformation sensor 3 is fed to a selector 5, which allows the polarity of the deformation pulse to be determined. From the output of the selector 5, the signal goes to one of the inputs of the OR 7 circuit, and from its output to the triggering input of the source 8 of the pulsed power supply. The indicated source is defined as a single rectangular pulse generator with triggering from an external trigger. A pulse from the output of the source 8 of the pulsed power supply is fed to the input of the measuring circuit 1, and measurements can be made during the duration of this pulse. The time from the beginning of the power supply of circuit 1 to the moment of initiation of strain-transfer agents Ib is tj in where 2 is the distance between the primary deformation converter and the strain-transducer; v is the rate of propagation of deformation (sound) in the rod material. Thus, the beginning of the strain pulse in the area of the measuring circuit 1 will always be at the time when it is energized, i.e. is in working condition. In order to avoid loss of information, the pulse duration from the source 8 of the pulse power must exceed the total duration of the strain pulse and

delay time t The polarity selectors 5 and 6 must be configured to transmit pulses of different polarity so that the deformation pulse reaches the deformation sensor 4 and does not cause an electrical signal at the input of the pulse supply source 8. The presence of the second strain gauge 4 is explained as follows. In general, a number of cases need to investigate not only the direct, but also the reflected strain pulse. Upon reflection from the end of the rod, the pulse changes its sign. Reflected

the impulse causes an electrical signal from the deformation sensor 4 to be reversed: the sign that, having passed through the selector 6, is fed to the second input of the OR circuit 7, and then triggers the source B of the pulsed power, which again brings the circuit 1 to the ready state for measurements.

The use of the proposed device will improve the accuracy in measuring pulsed longitudinal deformations in various products, in particular in rods.

Claims (1)

DEVICE FOR MEASURING LONGITUDINAL DEFORMATIONS, comprising a measuring circuit connected in series with a strain transducer and a pulse power supply, characterized in that, in order to improve the accuracy of measuring pulse deformations, it is equipped with a first and second strain gauges located on the measurement object on both sides of the measuring circuit connected to them by 'two selectors and connected to their outputs by an OR circuit, the output of which is connected to the triggering input of the switching power supply. e