SU1281929A2 - Self-excited oscillator of string transducer - Google Patents

Abstract

The invention can be used to mechanically test materials and improve measurement accuracy. The device contains a bridge circuit 1 with a string 2 oscillating in the gap of the magnet 3, amplifier 4, frequency-to-voltage converter 5, detector 6, summing amplifier 7, reference voltage source 8, key circuits 9 and 10, amplitude discriminator 11, divider 12 frequency, pulse shaper 13, control circuit 14, string length meter 15 and multipliers 16 and 17. The introduction of new elements and the formation of new connections between the elements of the device allows the amplitude of the string oscillation to be maintained at a level that provides a predetermined error measuring the spine, regardless of the oscillation frequency and the length of the string. The invention is additional to the main auth.St. No. 953473, 1 Il. (C (L

Description

14)

The invention relates to a force-measuring technique, can be used in devices for mechanical testing of materials, and is an improvement of the device according to the author. St. No. 953473.

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

The drawing shows the circuit of the oscillator of the string Converter.

The self-oscillator of the string converter contains a bridge circuit 1 with a string 2 oscillating in the gap of the magnet 3, an input amplifier 4, a converter 5 frequency to voltage, an amplitude detector 6, a summing amplifier 7, a source 8 of the reference voltage, the first 9 and the second 10 key5 where and about

and, fO

and to -

15

The first key circuit 9 is associated with the stroke of summing amplifier 7, the output voltage of which is

U, K (Ug + Ug-UgJ.

reference voltage source 8;

the output voltage of the frequency converter 5 per voltage;

the voltage at the output of the amplitude detector 6; coefficient of proportionality.

In the absence of an absorption peak in the oscillatory process of the device, Uj Ug and then. When an absorption peak appears, U voltage increases by an amount proportional to the dissipation value of the energy at the absorption peak. This leads to an increase in the power supply voltage of the bridge circuit, and, consequently, the amplitude of the string oscillations until u5 becomes equal to U. At the same time, the device generally maintains the voltage of the balanced bridge diagonal proportional to frequency. A string length meter 15 with an analog output, for example, rheostatic inductive, capacitive, or any other type, provides measurements of the length of the string, for example, between nodes.

fasteners. Analog signal U output meter 15 string length

15

circuits, amplitude discriminator 11 with controlled voltage threshold, frequency divider 12, driver 13 pulses, control circuit 14, meter 15 struc- ture. we have analog output, first 16 and second 17 multipliers.

The self-generator string converter works as follows.

When the power is turned on, the pulse 30 excites the oscillation of the string 2. The presence of positive feedback formed when the second key circuit 10 is turned on leads to an increase in the amplitude of the oscillation of the string g 2. If the amplitude of the output voltage goes to the first and second inputs

If the amplifier 4 is less than the trigger threshold of the amplitude discriminator 11 with the trigger threshold of a controlled voltage, the auto-oscillator operates in a continuous mode of pumping energy to the oscillating string. The level of 1) the response of the amplitude discriminator 11 is determined by the output voltage of the second multiplier 45-17 analog signals. When the voltage at the output of the amplifier 4 reaches the threshold of the amplitude discriminator 11, the pulse sequence from its output after dividing 50 with the frequency divider 12 starts the pulse shaper 13, which gives

The first multiplier 16, the output signal of which with voltage U is supplied to the first input of the second multiplies l 17, to the second input of which supplies a signal from the output of frequency converter 5 to voltage.

In order that the relative error in measuring the frequency f due to an increase in the amplitude A of the oscillation does not exceed the allowable value & the amplitude of the string oscillation must satisfy the condition

 F2. f ./g;

Where

 And the length of the string;

string oscillation frequency, determined for a linear system;

an empty pulse of constant duration, the incoming control input of the first key circuit 9 and the input of the control circuit 14. The control circuit 14 triggers the second key circuit 10 and at the same time opens the positive feedback.

where and about

and o

and to -

five

The first key circuit 9 is connected to the output of summing amplifier 7, the output voltage of which is

U, K (Ug + Ug-UgJ.

source voltage reference 8;

the voltage at the output of the frequency converter 5 to voltage;

the output voltage of the amplitude detector 6; coefficient of proportionality.

In the absence of an absorption peak in the oscillatory process of the device, Uj Ug and then. When the absorption peak U appears, the voltage e U increases by an amount proportional to the energy dissipation at the absorption peak. This leads to an increase in the supply voltage of the bridge circuit, and, consequently, the amplitude of the string oscillations until u5 becomes equal to U. The device at the same time maintains the voltage of the balanced bridge diagonal proportional to the frequency. The meter 15 string length with analog output, for example, rheostatic, inductive, capacitive or any other types, provides a measurement of the length of the string, for example, between nodes

O

0 g goes to the first and second inputs

fasteners. Analog signal U output meter 15 string length

15

enters the first and second entrances

enters the first and second entrances

the first multiplier 16, whose output signal with voltage U is supplied to the first input of the second multiplier 17, the second input of which receives a signal from the output of frequency converter 5 to voltage.

In order that the relative measurement error of the frequency f due to an increase in the amplitude A of the oscillation does not exceed the allowable value & the amplitude of the string oscillation must satisfy the condition

 F2. f ./g;

Where

 And the length of the string;

string oscillation frequency determined for a linear system;

The permissible error of frequency measurement is due to an increase in the amplitude of oscillation (in relative numbers).

The output voltage of the second multiplier 1 7 analog signals

. . 12819294

Claims (1)

U, g Ug, proportional to Formula 1 f, is fed to the control input amplitude discriminator 11 with auto-oscillator of a string transformer “srabatagani”, controlled by a driver in auth.St. № 953473, about t l and zheniem. Thus, the threshold is determined by the fact that with the aim of the amplitude discrimination discriminator is measured in Pa 11 is supported by proportional entered serially connected the value of K-1 f-VS. . The value of the coefficient of length of the string, the first and proportionality coefficient K is given by the second multiplier, while the second depending on the string material, and the fO input of the second multiplier is connected to B. Depending on the permissible P-output of the frequency converter - measurement errors, and the output of the second multiplier. The device is generally under the control input of the amplitude holding the amplitude of the oscillation of the stringer and the amplitude at the level providing the specified f5discriminator is made. with a measurement error, independently by a poisonous threshold of the oscillation frequency and the length of the string.