SU1479856A1 - Device for remote measuring of movements - Google Patents

Abstract

This invention relates to a radio measuring technique. The purpose of the invention is to increase the sensitivity when measuring micro-movements. The device contains r-1 electromagnetic oscillations, a directional coupler 2, a transmission line 3, the characteristic impedance is equal to active resistance 4, as well as a resonant sensor made of inductance coil 5 and a capacitive transducer 6 with a variable gap. The rf voltage of mr 1 through the coupler 2 enters the line 3 and propagates in it in the form of an incident voltage wave. When it reaches the load of line 3, formed by resistance 4, coil 5 and converter 6, a reflected wave is formed, moving from the load to the coupler 2. At the initial gap value, there is no reflected wave and the device operates in the matching mode. When the gap changes due to the measured microdisplacements, the amplitude of the reflected wave changes, which reaches the coupler 2 and is released as an RF voltage at the output 7. 2 Il.

Description

J

four

CO 00 SP 05

1

-one

1147

The invention relates to radio engineering and can be used to measure distances and gaps between spaced objects.

The purpose of the invention is to increase the sensitivity when measuring micro-movements.

FIG. Figure 1 shows the structural electrical circuit of the device for remote measurement of movements; Fig. 2 shows graphical dependences of the output voltage on specific values of measured microdisplacements at given frequency values of a stabilized high-frequency generator and parameters of a capacitive converter of microdisplacements.

The device for remote measurement contains an electromagnetic oscillator 1, a directional branch 2, a transmission line 3, an active resistance 4 equal to the characteristic impedance of the transmission line 3, an inductance coil 5 and a variable-gap capacitive converter 6 connected in series. The output signal, which is linearly dependent on the measured micromotations, is removed from the output 1 of the reflected wave of the directional coupler 2. The capacitive transducer 6 is located, for example, over the conducting surface of the object 8 under test at the initial distance dQ from it.

A device for remote measurement of movements operates as follows.

The high-frequency voltage from the output of the stabilized generator 1 through the directional coupler 2 is fed to the input of the transmission line 3 and propagates in it in the form of an incident voltage wave. When it reaches the load of the transmission line 3 formed by the active resistance 4, the inductor 5 and the capacitive transducer 6, the formation of a reflected wave, moving

from the load to the directional coupler 2. The amplitude of this wave will be zero only at the initial gap value, when the inductor 5 and the capacitive transducer 6 are tuned to resonance. In this case, the total input resistance of the load is equal to the active resistance 4, i.e. 3 impedance line impedance. This mode is referred to as negotiation mode. There is no reflected wave in this case,

In any other case, when the gap value is not equal to d, a reflected wave arises, the amplitude of which depends on the changes in this gap ud, i.e. from measured microdisplacements. The reflected wave reaches the directional coupler 2 and is allocated in the form of high-frequency voltage at its output 7. To maintain uniqueness when measuring the microdisplacements, the gap is allowed to be reduced with respect to the initial value d0, i.e. The conductive surface of the monitored object 8 approaches the second electrode of the capacitive microdisplacement transducer 6 with a varying gap, or its increase from the minimum. To measure the vibrations, after adjusting the circuit to resonance at the initial gap d0, move the electrode of the capacitive transducer 6 by an amount equal to half the measurement range in the direction of the surface of the vibrating control object 8. In this case, the linearity of the characteristic is saved and the resulting constant component at the output A linear converter can be easily removed using a spacer (not shown). I

The amplitude of the reflected wave on

the input of the communication line as follows depends on the measured microdisplacements

 IWel-bd

IT

ll-U2ud

(one)

where is about

one

2pw6s

In order to isolate the voltage of the reflected wave at a separate output of the converter, a directional coupler 2 is used, connected between generator 1 and transmission line 3, which can be made according to the high-frequency balanced bridge circuit. The voltage transfer coefficient of the reflected wave to output 7

the directional coupler is constant and tends to unity. Then the expression describes the functional dependence of the output signal on the measured microdisplacements.

To obtain a linear relationship, it is necessary to achieve the following condition:

oL2-uoL2 «: 1

(2)

Given the dimensions of the capacitive converter 6 microdisplacement, the characteristic impedance of the transmission line 3, the dielectric properties of the insulator, this condition can be achieved by selecting the frequency of the output voltage of the generator 1

00 27f t

for which it is necessary to specify the admissible value of the nonlinearity error of the transformation.

Taking into account the expression (1), it is possible to obtain the frequency range of the output voltage of generator 1, which ensures the fulfillment of condition (2). The choice of any frequency from this range to build this generator 1 will allow to obtain the nonlinearity error in a given measurement range not worse than the permissible value. Thus, the frequency of the output voltage of the generator 1 is chosen from the condition

f

; (3)

where is the range of measured microdisplacements;

p is the characteristic impedance of the transmission line 3,

s is the area of overlap of the electrodes of the capacitive transducer 6; Ј - absolute dielectric

gap permeability; Допустnl permissible error of nonlinearity of conversion, in%,

Claims (1)

15 claims A device for remote measurement of displacements, comprising a series-connected electromagnetic oscillator, a directional coupler and a transmission line, an amplitude meter connected to the output of the reflected wave of the directional coupler, and a resonant sensor, characterized in that, in order to increase the sensitivity When measuring microdisplacements, the resonant sensor is made in the form of series-connected inductors and a capacitive converter; the resistance between the output of the transmission line and the input of the resonant sensor is equal to the characteristic impedance of the communication line. About Yu 20 30 Yu microns Fig 2.