SU1659820A1 - Apparatus to measure electrophysical parameters of current conduction media - Google Patents

Abstract

The invention relates to mechanical engineering and metallurgy, and more specifically to means of controlling the electrophysical parameters of conductive materials. The aim of the invention is to improve the measurement accuracy. The device consists of a tunable frequency generator, the output of which is connected to an indicator, a whirlwind transducer consisting of an inductance connected to the resonant circuit, and a broadband photo-shifting link. The output of the vortex converter is connected via an amplifier to the first input of the phase detector, and the output of the wideband phase-shifting element is connected to the second input of the phase detector. The output of the phase detector through the integrator is connected to the control input of the variable frequency generator. 3 Il. w Ё

Description

The invention relates to mechanical engineering and metallurgy, and more specifically to means of controlling the electrophysical parameters of conductive materials.

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

Fig. 1 shows a block diagram of the proposed device for measuring the electrophysical parameters of conductive media; Figures 2 and 3 show variants of a specific implementation of the eddy current transducer circuit.

The device consists of a series-connected variable frequency oscillator 1, an eddy current transducer 2, an amplifier 3 and a phase detector 4 with inputs, the second input of which is connected to the output of a variable frequency generator through a broadband phase-shifting link 5. The output of the phase detector 4 is connected via the integrator b to the control input of the variable frequency generator 1, and in addition, the input of the indicator 7 is connected to the output of the variable frequency generator 1.

Variable frequency oscillator 1 is a standard voltage controlled oscillator (VCO). As indicator 7, a frequency meter is used, for example 43-57.

Figures 2 and 3 show variations of the specific implementation of the eddy current transducer circuit 2. The eddy current transducer 2 is a divider with a switch in one arm

oh, ate

yoo ioo

| Yu

about

the resistor is R, and the other is the resonant LC circuit, and the inductance L is an eddy current coil.

The device works as follows.

When the device is turned on, the variable frequency generator 1 begins to generate a signal with a frequency corresponding to a zero signal at its control input, and the frequency of the variable frequency generator 1 is not equal to zero. The signal from the output of the variable frequency generator 1 is fed to the eddy current transducer 2, as well as to the input of a wideband phase-shifting unit, where its phase is shifted by 90 ° in the direction of advance.

If the frequency of the signal at the input of the eddy current transducer is not equal to the resonant frequency of the LC circuit, the signal from the output of the eddy current transducer 2, pre-amplified in amplifier 3, is fed to the first input of the phase detector 4 and has a phase difference with the signal at the second input of the phase detector 4 different from 90 ° In this case, a signal is generated at the output of the phase detector 4, which is equal to the product of the signals at both of its inputs. This signal is fed to the input of the integrator 6, where it is integrated. At the output of the integrator 6, a signal of a certain polarity is formed, depending on the phase difference at the first and second inputs of the phase detector 4. The signal from the output of the integrator 6 is fed to the control input of the variable frequency generator 1 and changes the frequency of the generator so that its frequency becomes equal to the resonance frequency of the LC circuit of the eddy current transducer 2

In the change mode, the coil of the eddy current transducer 2 is applied to the surface of the test medium, for example, a metal surface, the electrophysical parameters of which must be measured. In this case, eddy currents are formed in the medium (metal), the magnitude of which depends on the electrophysical parameters of the medium, such as electrical conductivity and magnetic permeability. The electromagnetic field of the eddy currents affects the coil of the vortex converter 2. The effect of this field is equivalent to a change in the active (ohmic) and reactance of the coil.

A change in reactance causes a mismatch in the LC resonant circuit, which causes the phase difference of the signals at both inputs of the phase detector 4, other than 90 °. As a result, a signal is generated at the output of the integrator 6, which provides for the restructuring of the variable frequency generator 1 in accordance with the new parameters of the eddy current coil

On a scale of indicator 7 (for which the frequency meter is used), previously calibrated in units of the parameter being measured, its value is recorded.

The instability of the variable-frequency generator 1 does not affect the measurement result, since the frequency of the output signal of the variable-frequency generator 1 sets the resonant circuit of the LC eddy current transducer, and secondly, the noise immunity of the eddy current transducer is increased due to the inclusion of its coil in the resonant circuit, which has the ability to suppress interference in the entire frequency range, except for a narrow frequency range near its resonant frequency; thirdly, the value of the measured parameter is determined by the frequency of the output signal la variable frequency oscillator 1 which is

measured with greater accuracy than the amplitude of the signal in the prototype in the fourth, the resonant circuit has a large steepness of the output characteristics

thirty

p f (Af).

where p is the phase of the output signal of the eddy current transducer;

At is the deviation of frequency from the resonant one (detuning by frequency).

Greater dependency steepness

p f (A f)

reduces the instability of the elements of the amplifier 3, the phase detector 4 and the integrator 6.

In addition, the nonlinearity of the output characteristics of the phase detector 4 also

does not affect the measurement accuracy due to the fact that the signal from the output of the phase detector 4 is fed to the integrator 6.

Claims (1)

An apparatus for measuring the electrophysical parameters of conductive media, comprising a series-connected sinusoidal oscillation generator, an eddy current transducer, an amplifier and a phase detector, the second input of which is connected to the output of the sinusoidal oscillation generator as well as the indicator measurement accuracy, as a generator of sinusoidal oscillations, a variable frequency generator is used, the control input of which is Through an integrator connected to the output of the phase detector, and the output is connected to an indicator, in which A frequency meter is used, the eddy current transducer is designed as a divider, with a resistor included in one arm and a LC circuit in the other, and the phase-shifting link is broadband. 0ml R -4ZZ Fig Phie. i KZ From 7 KZ Fig.Z