SU1339464A1 - Method of adjustment of self-excited oscillator metal detector - Google Patents

Abstract

The invention relates to electronic engineering and is implemented in a device comprising an oscillating circuit I of an autogenerator (A) with a sensor 2 in the form of an inductor, a nonlinear element 3 (transistor) and a feedback circuit including an amplitude adjustment unit 4 and a phase adjustment unit 5 feedback. The goal is to increase the sensitivity of the device. To achieve it, the adjustment range A is determined from the minimum of the measured amplitudes until the oscillations are completely broken A. A resistor () of feedback A is fixed in the middle of the obtained range, a resonant curve of the oscillating circuit A is obtained in the absence and presence of the detected object in the sensor detection zone and determine the resonant frequencies and the sign of the difference between them. By using a phase shifter in feedback circuit A, the phase shift is increased until the frequency shift sign at output A is reversed. At the same time, the magnitude of the output signal in the absence of a recorded object is changed by increasing the resistance of the feedback, increasing its resistance, the phase shift and the feedback magnitude of the feedback P are recorded at the maximum of the amplitude change. 2 Il. From sl oe oo with 4 O5 4: (pus.Z

Description

one

The invention relates to electronic engineering and can be applied for the registration of manufactured metal parts in metering systems of discrete production.

The purpose of the invention is to increase the sensitivity by taking into account both active and reactive resistance introduced by a metal object into the coil of the oscillating circuit of a self-generating metal detector.

Figure 1 shows the resonance curves when setting up the metal detector; 2 is a block diagram of a device, an implementation; its proposed method.

Changing the feedback phase of the autogenerator metal detector (Fig. 1, it can be excited at a frequency different from the resonant frequency of the oscillating circuit of the autogenerator metal detector. When a metal object is introduced into the detection area of the sensor, the resonant curve of the oscillating circuit formed by the sensor inductance of the sensor and the autogenerator capacitance changes cushion in magnitude and creep relative to its original position, forming a family of resonant characteristics.

The frequency of the autogenerator metal cannot change instantaneously due to the presence of a delay t in its circuits, and first of all, a delay in the feedback circuit of the autogenerator, which will lead to additional attenuation in the oscillatory circuit with the metal object by shifting the resonance curve by the value of dAf (change amplitude due to the change in the frequency of the auto-detector metal) to lL (9, which is caused by the introduction of the equivalent resistance Rj into the inductance of the oscillating circuit with a metallic conductor). DMetI.

Thus, the operating frequency of the autogenerator metal detector should be shifted relative to the resonant frequency of the oscillating circuit in CTopoiiy, opposite to the shift of the resonance curve when a metallic object appears. Necessary to detect a metal object with an auto-generator metal detector were auto-oscillations,

394642

contributing to the fact that the operating point (Fig. 1) on the resonance curve should be located above the line, correspondingly to the amplitude balance conditioner. The device (ttiHr.2) contains an oscillating circuit 1 of an auto-oscillator with a sensor 2 in the form of an inductance coil entering the oscillatory circuit, a nonlinear element 3 (transistor) and a feedback circuit including an amplitude adjustment unit 4 and a phase adjustment unit 5 feedback.

) ti The device works as follows.

Configure the auto-oscillator metal detector. To do this, change the resistance value of the resistor in

20 feedback circuit of the oscillator, measure the amplitude of the output signal of the oscillator without a registered object and, when the object is inserted, into the detection zone of sensor 2. They determine the adjustment range of the oscillator from the minimum difference of the measured amplitudes until the oscillator oscillates, fixing the resistor value in the reverse connection

30 block 4 autogenerator metal detector, in the middle of the resulting range. Get the resonance of the ith curve L (G) of the oscillating circuit of the oscillator in the absence and in the presence of

For a registered object in the detection zone of sensor 2. It is determined at

by this

resonance frequencies f and fj

the sign of the difference between them is uf f -fj. Phaser in the feedback circuit

The autogenerator metal detector unit 5 increases the phase shift in such a way that the shift at the output of the autogenerator is set opposite to the sign of Lf. Consistently

increasing the resistance value of the resistor RP and the value of the phase shift / s /, the magnitude of the output signal amplitude in the absence of the object and its change upon introduction are measured

subject. The adjustment is terminated at a maximum change of 1 amh: itd, which corresponds to a maximum of sensitivity.

By setting up the oscillator in

The working area of the sensor 2 is oscillating about the circuit 1 that is being recorded. At the same time, to the main change in amplitude due to the introduction of active resistance

31

The kL adds a change in amplitude Af due to tuning the oscillator on the slope of the resonant characteristic of the oscillating circuit, where the slope of the characteristic A (f) is greater than at the top of the resonant characteristic of the oscillating circuit.

Formulas

the invention

The method of setting the autogenerator metal detector, which consists in measuring the amplitude of the output signal of the autogenerator without a registered object and entering it into the detection zone, characterized in that, in order to increase the sensitivity, the adjustment range of the autogenerator is determined from the minimum difference of the measured amplitudes to the complete disruption of the oscillator of the autogenerator, fixed size

in the middle of the received range, the feedback oscillator of the autogenerator receives the resonant curve A (f) of the oscillator circuit of the oscillator in the absence and presence of a detectable object in the sensor detection zone, the resonant frequencies f and fj and the sign of the difference between 1Q them / jf f 1 f ,, using a phase shifter in the feedback circuit of the oscillator, increase the phase shift until the sign of the frequency shift at the oscillator's output changes to the opposite sign / 1 f, while changing the size of the feedback resistor, increasing Its resistance, measure the magnitude of the amplitude of the output signal in the absence of a detectable object and its change when it is inserted, record the phase shift and the value of the feedback resistor at the maximum change in the magnitude of the amplitude,

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FIG. one

Editor N.Rogulich

Compiled by A. Romanov

Tehred L. Oliynyk Proofreader A.Zimokosov

Order 4215/34 Circulation 730 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Project, 4

/

Claims (1)

The method of tuning the self-generating metal detector, which consists in measuring the amplitude of the output signal of the self-oscillator without a registered object and when entering it into the detection zone, characterized in that, in order to increase the sensitivity, the adjustment range of the self-oscillator is determined from the minimum of the difference in the measured amplitudes to a complete breakdown of the oscillator oscillations, the value is fixed re339464 9 of the oscillator feedback resistor in the middle of the obtained range, a resonance curve A (f) of the oscillatory circuit of the oscillator is obtained oscillator ³ in the absence and in the presence of a registered object in the detection zone of the sensor, determine the resonant frequencies f and f and the sign of the difference between them δϊ = f, - f,, using the phase shifter in the feedback loop of the oscillator, increase the phase shift until the sign of the frequency shift changes by the output of the oscillator opposite to the sign Δ f, at the same time they change the value of the feedback resistor, increasing its resistance, measure the amplitude of the output signal in the absence of a registered 2Q object and its change when making him, fix the phase shift and the value of the feedback resistor at the maximum change in the magnitude of the amplitude.