SU1390547A1 - Humidity meter - Google Patents

Abstract

This invention relates to a microwave measurement technique. The purpose of the invention is to improve the measurement accuracy, the Meter contains a resonator (P) 1, single-band modules 2 and 3, dividers 4-7 frequencies, low-frequency generator 8, synchronous detector 9, recorder 10, microwave detector P, band-pass filter 12, phase shifter 13 limiter 14, phase detector 15, low-pass filter 16, adder 17, microwave generator 18, directional coupler 19. To achieve the goal, the input of modulator 2 is connected to the second input of detector 11, the second input of modulator 3 is connected to output P 1, the input of the divider 5 is connected to the output of the generator 8. The signal from generator 18 through coupler 19 excites P 1 associated with material 20. Depending on the humidity of the material 20, the quality factor P 1 changes. Thus, by measuring the quality factor P 1, it is possible to determine the moisture content of the material 20. 2 Il. 20 . (L

Description

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The invention relates to a technique for measuring on microwave and can be used in microwave moisture measurement to control the humidity of various materials.

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

FIG. 1 shows the structural electrical circuit of the meter of the damper 19, frequency-shifted by the modulator 2. As a result, a signal appears at the output of the microwave detector 11 at the frequency of the oscillator 8 with a shift that is proportional to the design of the microwave generator 18 relative to the natural frequency of the resonator. through phase shifting

nosti; in fig. 2 - diagrams, according to LN 3 and limiter 14 arrives at

for his work.

The moisture meter contains a resonator 1, first 2 and second 3 single-sided modulators, first 4, second 5, third 6 and fourth 7 frequency dividers, low-frequency generator 8, synchronous detector 9, recorder 10, microwave detector 11, band-pass filter 12, phase shifter 13, limiter 14, phase detector 15, low-pass filter 16, adder 17 Microwave generator 18, directional tap 19, as well as the material under study 20.

Figure 2 shows: spectrum 21 is the signal at the output of the resonator 1; spectrum 22 is the signal at the output of the second single-band modulator 3; spectrum 23 is the signal at the output of the first single-band modulator 2; с,, с - residues, respectively, of an incompletely suppressed carrier and mirror signal; - natural frequency of the resonator 1; - the frequency of the useful signal at the output of the microwave detector 1 1.

The meter works as follows.

The signal from the output of the microwave generator 18 through the directional coupler 19 b excites the resonator 1 associated with the material under study 20. Depending on the humidity of the latter, the quality factor of the resonator 1 changes. Thus, measuring the latter, the humidity of the material under study 20 is determined.

The quality factor of the resonator 1 is measured by the slope of its phase-frequency characteristic, which is proportional to the quality factor. For this, the microwave generator 18 is tuned to resonance with resonator 1 using a phase locked loop (PLL); from the output of the resonator 1 is shifted in phase (the shift is proportional to the mutual detuning of the resonator 1 and microwave generator 18), the signal goes to the microwave detector 11,} ia another, whose signal is received from the mercury coupler 19, shifted in frequency by the modulator 2. As a result, the output of the microwave detector 11, a signal appears at the frequency of the generator 8 with a phase shift proportional to the detuning of the microwave generator 18 relative to the natural frequency of the resonator 1. The indicated signal through the phase shifter

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the input of the phase detector 15, the reference input of which receives a signal from the frequency divider 7, resulting in the output of the detector 15 produces a voltage proportional to the detuning of the microwave generator 18 relative to the natural frequency of the resonator 1, which through the filter 16 and the adder 17 enters the control input Microwave generator 18 and changes its frequency until it becomes equal to the natural frequency of the resonator 1.

In addition, the signal from the output of generator 5 through the frequency divider 6 and the adder 17 is fed to the microwave generator 18, causing it to deviate. The PLL loop does not compensate for this deviation due to the introduction of the filter 16. The frequency deviation causes a phase deviation at the output of the resonator 1, which is proportional to the slope of its phase-frequency characteristic, i.e. its good quality. This deviation is allocated at the output of the phase detector 15 and through the synchronous detector 9 enters the register 10.

However, at the outputs of modulators 2 and 3 there are also signals at carrier and mirror frequencies with levels (n and Si, respectively,

leads to measurement error.

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In order to compensate for this, the signal from the output of the generator 8 is fed to the single-band modulator 3 through the divider 5 frequencies by three, and to the single-sided modulator 2 through the divider 4 frequencies. The spectra 22 and 23 of the signals at the outputs of the modulators 2 and 3, respectively, have the form shown in FIG. 2. If the frequency of the oscillator 8 is conditionally taken equal to 6-Q, the useful signal at the output of the microwave detector 11 has a frequency (difference between the frequencies of the input signals). From the output of the microwave detector 11, the filter 12 extracts the signal at the frequency SL, which through the phase shifter 13 and the limiter 14 enters the phase detector 15, to another input which is 5

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A signal with frequency i2 is obtained by dividing the frequency into six by a divider 7.

Only two signals fall into the transparency band of filter 12, which is tuned to frequency j7.

k r.osCQt + H)

k (co8 (at +% -%),

where k is the proportionality coefficient.

The first of the signals is useful (H carries information about humidity and the second interferes, but now it does not depend on the quality of the suppression of the carrier.

Fsgrmula invention

A moisture meter containing a series-connected microwave detector, a band-pass filter, a phase shifter, a limiter, a phase mat, a microwave generator, a directional coupler, and a resonator connected to the material under study are connected in series to a low-frequency one.

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generator, first frequency divider and first single-band modulator, the second input of which is connected to the output of the secondary path of the directional coupler, serially connected second frequency divider and second single-band modulator, the output of which is connected to the first input of the microwave detector, serially connected third frequency divider, input which is connected to the output of the low-frequency generator, a synchronous detector, the second input of which is connected to the output of the phase detector, and the recorder, as well as the fourth divider hour The input is connected to the output of the low-frequency generator and the output is connected to the second input of the phase detector, and the second output of the third frequency divider is connected to the second input of the adder, characterized in that, in order to increase the measurement accuracy, the output of the first single-sided modulator is connected to the second the input of the microwave detector, the second input of the second single-sided modulator is connected to the output of the resonator, and the input of the second frequency divider is connected directly to the output of the low-frequency generator,

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Compiled by V. Goncharov. Editor N. Rogulich Tekhred M. Didyk Proofreader S. Shekmar

Order 1761/43

Circulation 847

VNIIPI USSR State Committee

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

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about ;, f t25

+ 3Si

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Claims (1)

A moisture meter containing a serially connected microwave detector, a bandpass filter, a phase shifter, a limiter, a phase matrices, a microwave generator, a directional coupler and a resonator associated with the test material, a low-frequency generator, a first frequency divider and a first single-band modulator, the second input of which is connected in series connected to the output of the secondary path of the directional coupler, the second frequency divider and the second single-band modulator, the output of which is connected to the first input of the microwave detector, the third frequency divider, the input of which is connected to the output of the low-frequency generator, a synchronous detector, the second input of which is connected to the output of the phase detector, and the recorder, as well as the fourth frequency divider, the input of which is connected to the output of the low-frequency generator, and the output is with the second input of the phase detector, the second output of the third frequency divider connected to the second input of the adder, characterized in that, in order to improve the accuracy of measurements, the output of the first one a band modulator is connected to the second input of the microwave detector, the second input of the second single-band modulator is connected to the output of the resonator, and the input of the second frequency divider is connected directly to the output of the low-frequency generator.