SU1147941A1 - Device for measuring oscillation logarithmic decrement - Google Patents

Abstract

A DEVICE FOR MEASURING THE LOGARIFMIC DEFENSE OF VIBRATIONS, containing two circuits, one of which includes a series-connected amplifier and detector, the other — a coincidence unit and a register; limiter connected between the output of the amplifier and the first input of the coincidence block, the element EXCLUSIVE OR, the inputs are connected to the outputs of the comparators, and the output to the second input of the match block The integrator is connected to the detector output and to the first inputs of the comparators, the power source and the voltage divider connected to it, and the two outputs of the voltage divider are connected to the second S inputs of the comparators, respectively. (L

Description

The invention relates to measuring technique and can be used in the study of the elastic properties of materials.

A device is known for measuring the $ logarithmic decrement of oscillations, which contains two circuits, one of which includes an amplifier and a detector, the second - a coincidence unit and a recorder, and two comparators fl J. connected by the first inputs jq.

The disadvantage of this device is its low accuracy due to fluctuations in the level of response of the comparators and the uncertainty of the trigger in time.

The purpose of the invention is to improve the accuracy of measurements.

The goal is achieved in that the measuring device ₂ θ logarithmic decrement namic comprising two chains, one of which includes posledovatepno connected amplifier and detector, and the other block matches the registrar and soe- ₂₅ pervmi union of two inputs of a comparator provided usilitelem- limiter vklochennym between the amplifier output and the first input of the coincidence circuit, the exclusive OR element, the inputs connected to the outputs kompa- tors ^30, and output - to the second input of the coincidence circuit, an integrator, connected th to the output of the detector and to the first input of the comparator, the power source and the connected voltage divider 35, and two voltage divider outputs are connected to second inputs of comparators respectively.

The drawing shows a block diagram of a device.

A device for measuring the logarithmic decrement of oscillations containing two circuits, one of which includes a series-connected amplifier 1 and detector 2, the other a coincidence unit 3 and a recorder 4, and two comparators 5 and 6 connected by the first inputs, equipped with a limiter amplifier 7, turned on by the 50th between the output of amplifier 1 and the input of block 3 of matches, element 8 EXCLUSIVE OR, the input connected to the outputs of comparators 5 and 6, and the output to the second input of block 3 of 55 matches, an integrator 9 connected to the output of detector 2 and to th inputs of comparators 5 and 6, ix • 41 2 and the source of power 10 connected thereto a voltage divider 11, and two divider output 11 connected to second inputs of comparators 5 and 6 respectively.

A device for measuring the logarithmic decrement of oscillation works as follows.

The exponentially damped signal amplified by the amplifier 1 and detected by the detector 2 is fed to the input of the integrator 9, and from its output to the first inputs of the comparators of the upper 5 and lower 6 levels. The second inputs of these comparators are supplied with constant voltages and ^^ and U _R through a resistive divider. 11 from the source 10. The resistance of the divider is chosen the same, so the ratio of potentials at the second inputs of the comparators 5 and 6 is equal to two and remains always constant regardless of the variations of the output voltage source 10. The voltages from the outputs of both comparators 5 and 6 are fed to the input of element 8 EXCLUSIVE OR, which generates a rectangular pulse with a duration equal to the ratio in,.

T - B. tn2 сЛ £ 'where U _2R is the operating voltage of the upper level comparator;

Up - lower voltage of the comparator;

сА - logarithmic decrement of oscillation;

f is the frequency of the decaying process. For the duration T of this pulse, a coincidence circuit 3 is unlocked, the second input of which receives pulses generated by the amplifier-limiter 7 with the frequency of the damping process. Thus, at the output of the coincidence circuit 3, a packet of pulses is allocated, the number N of which is equal to the number of periods of the damped process during the time until its amplitude decreases by half. Therefore, the logarithmic decrement of the oscillation of SL is: SL - ² -.

N

From the coincidence circuit 3, these pulses arrive at the recorder 4.

The main advantage of the invention is to increase accuracy due to the rigid maintenance of the ratio of the thresholds of operation of the comparator of the upper and lower levels.

Claims (1)

DEVICE FOR MEASUREMENT OF THE LOGARITHMIC DECREAM OF VIBRATIONS, containing two circuits, one of which includes a series-connected amplifier and detector, the other - a coincidence unit and a recorder, and two comparators connected by the first inputs, characterized in that it is equipped with the aim of increasing the measurement accuracy limiting amplifier connected between the output of the amplifier and the first input of the coincidence unit, the EXCLUSIVE OR element, the inputs connected to the outputs of the comparators, and the output to the second input of the coincidence unit, integr ator connected to the output of the detector and to the first input of the comparator, the power source and the connected voltage divider, and two output divisors _la vtorm voltage connected to the inputs of comparators, respectively. SU, 1147941 1 in;