SU1486955A1 - Digital quality meter - Google Patents

Description

The invention relates to measuring equipment. The purpose of the invention is to reduce the measurement error. The meter contains a generator

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1 variable frequency, measured case 2,. Computing unit 3, control unit 4, local oscillator 5, harmonic driver 6, mixer 7, electron-counting frequency meter 8, integrating circuit 9, functional converter 10 and voltage-frequency converter 11. The introduction of converter 11 into the device made it possible to reduce the frequency instability of the local oscillator by reducing its tuning range and, consequently, reducing the measurement error of the quality factor. The electron-counting frequency meter operating in the frequency ratio measurement mode. 2 Il.

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The invention relates to measurements of electrical and magnetic quantities, in particular to the measurement of quality factor.

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

FIG. 1 shows a functional diagram of the device; see 2a diagram explaining the operation of the device.

Digital Q-meter contains in series -. variable frequency generator 1, (measured circuit 2, computing unit 3, control unit 4, local oscillator 5, driver 6, harmonics, mixer 7, electron-counting frequency meter 8 and integrating circuit 9 in series, functional converter 10, converter 11 voltage - frequency, the output of which is connected to the third input of the electron-counting frequency meter 8. The input of the integrating circuit 9 is connected to the control input of the variable frequency generator 1. The second input of the mixer 7 is connected to the output of the generator 1. The second od electron counting frequency meter 8 is connected to the second output of the computing unit 3, and a second input unit 4 connected to the output of the mixer 7 "

Computing unit 3 contains series-connected peak detector 12, voltage divider 13, comparison unit 14, and differentiating circuit 15. Control unit 4 consists of series-connected linearly varying voltage generator 16, impulse generator 17, coincidence element 18.

Digital Q-meter works as follows.

At the first stage of measurements, the average frequency of the oscillator 1 is set near the resonant frequency of the circuit under investigation using an oscilloscope, the horizontal scan input of which is connected to the control output of the generator 1, and the vertical scan input to the output of the measured circuit 2.

The signal from the output of the generator 1 with a frequency of £ _ghp enters the "measured circuit 2 and the mixer 7. From the output of the measured circuit 2, the detected signal enters the computing unit 3, which receives pulses at times when the frequency of the generator 1 is £ and £ 2 '

(Fig. 2). The positive impulse from the output of the differentiating circuit 15, corresponding to the frequency £ _ГПч = £, goes to block 4, the negative pulse from the output of the differentiating circuit 15, corresponding to the frequency £ _{ГП1 |} = £ ₂ =

= £ ₁ + 2а £ ₀ , starts the electron-counting Frequency Meter 8, the input of which receives a signal from the output of the mixer 7 with a frequency equal at this moment £ _cm = £ _gfc - £ _r er ' ⁿ " ^r D ^{e n} " is the frequency range of the local oscillator five

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The pulse shaper 17 generates a pulse at the moment when the frequency of the signal at the output of the mixer 7 is Ήνπιο (£ _cm = 0). The generator 16 of a linearly varying voltage changes its output voltage and thus the frequency of the local oscillator 5 until the pulse from the driver 17 and the positive pulse from the output of the differentiating circuit 15 do not coincide in time, which corresponds to the frequency of the local oscillator 5, equal to £ _het = £ ι / η. _{l the} frequency of the signal at the output of the mixer at the time of its measurement by the frequency meter 8 is equal to

£ CM ~ £ Ί ~ ^- Ί 1 ~

= £ 24 _oh . '

The control voltage P - ^ lr of the variable frequency generator I in the form of a large constant component, determining the average frequency close to the resonant frequency of the measured contour and minor sawtooth component defining the sweep band, is fed to the integrating circuit 9, the output of which is a constant component control voltage generator I variable frequency, which is fed through the functional Converter 10 to the input of the voltage Converter - frequency 11. In general, Har the act of adjustment of the generator 1 of the variable frequency £ _gpc = u, (C ^ lr) is nonlinear.

The output of the functional Converter 10 generates a voltage G FP = K, · £ _gpch , proportional to the average operating frequency of the generator 1, At the output of the converter 11 voltage-frequency there is a signal with frequency £ _6ЫУ = К '£ _р .

The input of the electron-counting frequency meter 8, operating in the mode of measuring the ratio of two frequencies, receives two signals with frequencies £

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2L £ about. Electron-counting frequency meter 8 shows the digital value N "where K ₂ a 1,

for example, K _g = 10 ' ³ . Choosing the multiplier of the counting electron-counting frequency counter, equal to u = 1 / K ₂ , we get N = £ _0/24 £ „= P _in , -th. the readings of the electron-counting frequency meter 8 correspond to the measured value of the quality factor%, K, K /, K _g - the proportionality coefficients.

The use of a DC-to-frequency converter in the proposed device allows to reduce the range of electronic adjustment of the local oscillator and thereby increase its stability and reduce the error in measuring the quality factor.

Claims (1)

Claim Digital Q-meter, containing series-connected1486955 ⁶ variable frequency generator, terminals for connecting the measured circuit, a computing unit, a control unit, a local oscillator, a .5 harmonic driver, a mixer and an electronic counter frequency meter and an integrating circuit and a functional converter connected in series, 10 than the input of the integrating circuit is connected to the control output of the variable frequency generator, the second input of the mixer is connected to the output of the variable frequency generator, the second input 15 of the electron-counting frequency meter is connected to the second output of the computational block ka, and the second input control unit connected to the output of the mixer, characterized in that, in order to increase the accuracy iz20 25 the measurement, the voltage converter is introduced into it - the frequency, the input of which is connected to the output of the functional converter, and the output to the third input of the electron-counting frequency meter.