SU1525453A2 - Device for measuring linear displacements - Google Patents

Abstract

The invention relates to a measurement technique, can be used in devices for automatically measuring linear displacements, and is an improvement of a device for measuring linear displacements along an. N 1179106. The aim of the invention is to improve the measurement accuracy by eliminating the error caused by a change in external conditions. The signals from the interdigital transducers 2 and 5 are fed to the formers 11 and 12, which generate pulses with a duration equal to the propagation time of the signals. In adder 15, these durations are subtracted, in adder 16 - their addition, and in divider 17 - the output signal of adder 15 is divided by the output signal of adder 16. The result of the division does not depend on changes in the external operating conditions of the device. 1 il.

Description

one

(61) 1179106

(21) 4411905 / 25-28

(22) 04/18/88

(46) 30. P. 89. Bull. No. 44

(71) Kuibyshev Institute of Railway Engineers

(72) A.P., Andreev

(53) 534.232 (088.8)

(56) USSR Author's Certificate No. 1179106, cl. G 01 B 17/00, 1985.

(54) DEVICE FOR MEASURING LINEAR 1 SHREMPSh; nga1

(57) The invention relates to a measuring technique, can be used in devices for automatically measuring linear displacements, and is an improvement of a device for measuring linear displacements according to auth. No. 1179106. The purpose of the invention is to improve the measurement accuracy by eliminating the error caused by a change in external conditions. The signals from the interdigital transducers 2 and 5 are fed to the formers 11 and 12, which generate pulses with a duration equal to the propagation time of the signals. In the adder 15, these durations are subtracted, in the adder 16 - their addition, and in the divider 17 - the output division the signal of the adder 15 to the output signal of the adder 16. The result of the division does not depend on changes in the external conditions of the device operation. 1 il.

W

ten

Yah x L ate

The invention relates to a measurement technique, can be used in devices for automatically measuring linear displacements, and is additional to the author. St. 1179106.

The purpose of the invention is to improve the measurement accuracy by eliminating the error caused by a change in external conditions.

The drawing shows a functional diagram of a device for measuring linear displacements.

The device contains the first piezo plate 1, the first interdigital pin, the transducer 2 and the first absorber 3, the second piezo plate A, placed on it second. an interdigital transducer 5 and a second absorber 6, the capacitor 7 on the fixed plate 8 of which has the first and second piezo-plates 1 and 4, whose axes are oriented parallel to each other, and the movable plate 9 is made of two parts that are located above the piezoplates 1 and 4 with the possibility of transferring in a plane parallel to the fixed plate 8 of the capacitor 7, a pulse generator 10, the output of which is connected to the inputs of the first and second interdigital transducers 2 and 5, the inputs of the formers 11 and 12, The other inputs of which are connected to parts 13 and 14 of the movable plate 9 of the capacitor 7, and the outputs of the formers 11 and 12 are connected to the direct inputs of the first adder 15, the direct and inverse inputs of the second adder 16, the outputs of both the adder 15 and 16 are connected to the inputs of the divider 17 , the output of which is connected to the input of the registration unit 18. Piezoplastins 1 and 4 are made in the form of wedges, a simple angle

, d.,. the locators are installed at the tops of piezoplates. Parts 13 and 14 of the movable plate 9 of the capacitor 7 are connected to a moving object (not shown) by means of a dielectric rod 19.

A device for measuring linear displacements operates as follows.

Upon receipt of electrical pulses from the pulse generator 10 on the first and second interdigital transducers 2 and 5 on the pieeoplastic oppositely oriented

at the top of 3-30 °, and scavengers

0

five

0

five

0

five

0

1 and 7 create flows of oppositely directed surface acoustic waves, which are extinguished at the vertices of piezoplates 1 and 4 by absorbers 3 and 6. The traveling streams of surface acoustic waves on piezo plates 1 and 7 create flows of oppositely directed spatially-periodic electric no-ft lei. On the fixed plate 8 of the capacitor 7 and the parts 13, 14 of the movable plate 9 of the capacitor 7, electric charges are generated.

In the initial state, the movable plate 9 of the capacitor 7 is set at an equal distance from the interdigital transducers 2, 5 through the dielectric rod 19, and when a controlled object is applied through the dielectric rod 19 to the movable plate 9 of the capacitor 7, the latter moves relative to the interdirectional converters 2 , 5, which leads to a change in the magnitude of the electric charge on the parts 13, 14 of the movable plate 9 and on the fixed plate 8 of the capacitor 7,

Shapers J1, 12 generate rectangular-shaped electrical signals, the duration of which is equal to the propagation time of acoustic surface waves from the interdigital transducers 2, 5 to sections of piezoplates 1, 4, over which parts 13, 14 of the movable plate 9 of the capacitor 7 are located. In the first adder 15, the durations T and T of the pulse signals formed by the former J1 and 12 occur,

- T,

S (

v3

s

Vo6

five

five

(,.,) (,,) J

V where v

2- X

0

the propagation velocity of surface acoustic waves in piezoplates; S ,, S, are the distances of the receivers from the emitters of acoustic waves;

a is the initial displacement of the transducer by displacement; X - measured linear displacement.

In the second adder 16, the pulse durations are summed:

T, + T,

-Si,

Si

- i; t-x). (a - X). | -.

In the divider 17, the output signal of the first adder 15 is divided by the output of the second adder 16 and the output signal of the entire device is generated.

TR T.

2x Vei V72a

X

but

kx

independent of the effect of disturbing factors on the parameters of the transducer and, therefore, on the speed of propagation of surface acoustic waves in the piezoelectric plates of the transducer.

Thus, when a second adder and a divider is introduced into a known device, the accuracy of measuring

This is due to the increased stability of the device, its complete invariance to the effects of disturbances, the independence of the output signal of the device on the speed of propagation of surface acoustic waves in the piezoelectric plates of the transducer.

Claims (1)

Formula invented A device for measuring linear displacement along .св. No. 1179106, which is due to the fact that, in order to improve measurement accuracy by eliminating the error caused by a change in external conditions, it is equipped with series-connected second adder, the inputs of which are connected to the output of the formers, and a divider, the second input of which is connected to the output of the first adder and the output is with the input of the registration unit.