RU2579359C1 - Method of measuring physical quantity - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention can be used for high-accuracy determination of various physical quantities. According to a method of oscillations are excited in the resonator at fixed frequency. At the change of the initial natural frequency of the resonator in fixed limits of [f _p1, f _p2] its amplitude-frequency characteristic, the area under it, which indicates the measured physical quantity. Resonator is waveguide resonator with terminal load with resistor X_H, area under the amplitude-frequency characteristic is defined according to the relationship

, where

- initial, at nominal value of the measured physical quantity, the value of X_H, [X_H1, X_H2] - fixed limits change X_H0, corresponding fixed limits [f _p1, f _p2], and

- amplitude of vibrations in a waveguide resonator if X_H0 end load.

EFFECT: technical result consists in simplification of measurement process.

1 cl, 2 dwg

Н - H

Description

The invention relates to measuring equipment and can be used for high-precision determination of various physical quantities. These include mechanical quantities, geometric parameters of objects, physical properties of substances, etc. They also include electrophysical and other parameters of controlled objects (materials, substances).

There is a method of measuring a physical quantity, which consists in placing a controlled object in a resonator (oscillatory circuit with lumped parameters, a volume or open RF, microwave resonator, etc.) and measuring the characteristics of this resonator (monograph: A. Brandt. Investigation of dielectrics at ultrahigh frequencies, Moscow: Fizmatgiz. 1963. pp. 37-144; Viktorov V.A., Lunkin B.V., Sovlukov A.S. Radio wave measurements of technological process parameters.M .: Nauka, 1989. P. 168-177. ) Among these characteristics are the intrinsic (resonant) frequency of oscillation, the quality factor of the resonator, etc., which may vary depending on the physical or (and) geometric parameters of the controlled object. In particular, a method for measuring a physical parameter is known, which consists in exciting oscillations in a resonator in the field of which a controlled object is placed, and recording one of the parameters of the amplitude-frequency characteristic (AFC). As a recorded parameter, use the natural (resonance) oscillation frequency of the resonator.

There is also a known measurement method (RU 2029247, 02.20.1995), which consists in exciting frequency-modulated oscillations in a resonator in a fixed frequency range and recording the area covered by the amplitude values during frequency deviation in the specified frequency range, i.e. area under the resonance curve. This method is characterized by a significantly greater sensitivity to the measured parameter compared to the method in which the resonant frequency of oscillation serves as an informative parameter.

The disadvantage of this method is its rather complicated implementation. It assumes the presence of a frequency-modulated oscillation generator connected to a resonator, which provides deviation of the oscillation frequency over a sufficiently wide range corresponding to possible values of the resonant frequency, depending on the value of the measured parameter.

A technical solution is also known (RU 2427851, 08.27.2011), which, by its technical nature, is closest to the proposed method and is adopted as a prototype. This prototype method consists in exciting frequency-modulated oscillations at a fixed frequency in the resonator, determining the amplitude-frequency characteristics when the initial resonant natural frequency changes within fixed limits, and recording the area covered by the amplitude values, i.e. area under the resonance curve.

The disadvantage of the prototype method is a rather complicated implementation, which, when measured using waveguide resonators, can be simplified: changing the initial natural frequency of the resonator within fixed limits is possible in this case by measuring the final load parameters of such a resonator.

The technical result of the present invention is to simplify the measurement process.

, где

- начальное, при номинальном значении измеряемой физической величины, значение Х_н, [Х_н1, Х_н2] - фиксированные пределы изменения Х_н0, соответствующие фиксированным пределам [f_p1, f_p2],

- амплитуда колебаний в волноводном резонаторе при величине Х_н0 оконечной нагрузки.The technical result in the proposed method of measuring a physical quantity is achieved by exciting oscillations in the resonator at a fixed frequency, while changing the initial natural frequency of the resonator within the fixed limits [f _p1 , f _p2 ], its amplitude-frequency characteristic is determined, and the area under it is calculated by which judge the value of the measured physical quantity, as a resonator use a waveguide resonator with an end load with reactance X _n , the area under the amplitude-frequency characteristic sticks are found according to the ratio

where

- the initial, at the nominal value of the measured physical quantity, the value of X _n , [X _n1 , X _n2 ] - fixed limits of change of X _n0 corresponding to the fixed limits [f _p1 , f _p2 ],

- the amplitude of the oscillations in the waveguide resonator at a value of X _n0 terminal load.

The proposed method is illustrated by drawings.

In FIG. Figure 1 shows a graph of the dependence of the amplitude of the oscillations on the initial value of the reactance of the final load of the waveguide resonator.

In FIG. 2 shows a diagram of a device for implementing the proposed method.

Shown here are waveguide resonator 1, waveguide 2, termination 3, generator 4, functional element 5, detector 6, integrator 7, recorder 8.

The method is implemented as follows.

собственной (резонансной) частоты f_p волноводного резонатора и вычисляют площадь S под ней, по которой судят о значении измеряемой физической величины х. В предлагаемом способе в качестве резонатора применяют волноводный резонатор 1, образованный волноводом 2 с оконечной нагрузкой 3, имеющей реактивное сопротивление Х_н. От величины Х_н зависит значение частоты

волноводного резонатора. В общем случае оконечной нагрузкой волноводного резонатора может являться комплексное сопротивление Z_н=R_н+jХ_н, где R_н - активная составляющая Z_н. Именно реактивная составляющая Х_н комплексного сопротивления Z_н влияет на значение

и ее изменение при изменении Х_н.Oscillations of a fixed frequency f are supplied to the waveguide resonator from a generator of a fixed frequency. When this frequency f coincides with the natural (resonant) frequency f _{p of the} waveguide resonator, the amplitude A of the oscillations in it takes the maximum value A ₀ . According to the proposed method, as in the prototype method, the oscillations are excited at a fixed frequency f, its amplitude-frequency characteristic is determined when the initial value changes [f _p1 , f _p2 ] in a fixed range

natural (resonant) frequency f _{p of the} waveguide resonator and calculate the area S below it, which is used to judge the value of the measured physical quantity x. In the proposed method, a waveguide resonator 1 formed by a waveguide 2 with an end load of 3 having a reactance of X _{n is} used as a resonator. The value of frequency depends on the value of X _n

waveguide resonator. In the general case, the end load of the waveguide resonator can be the complex resistance Z _n = R _n + jX _n , where R _n is the active component of Z _n . It is the reactive component X _n complex resistance Z _n affects the value

and its change when changing X _n .

и, соответственно, пределы [Х_н1, Х_н2] изменения начального значения

величины Х_н должны соответствовать диапазону возможных значений [х₁, х₂] измеряемой физической величины х. На фиг. 1 приведен график функции

при изменении

в фиксированных пределах [Х_н1, Х_н2], соответствующих пределам [f_p1, f_p2] изменения частоты

. Максимальное значение амплитуды А=А₀ имеет место при значении

, то есть на частоте

, равной фиксированной частоте f генератора.The limits of [f _p1 , f _p2 ] changes in frequency

and, accordingly, the limits [X _n1 , X _n2 ] changes in the initial value

X _n values must correspond to the range of possible values [x ₁ , x ₂ ] of the measured physical quantity x. In FIG. 1 shows a graph of the function

when it changes

within the fixed limits [X _n1 , X _n2 ] corresponding to the limits [f _p1 , f _p2 ] changes in frequency

. The maximum value of the amplitude A = A ₀ takes place at a value

, i.e. at a frequency

equal to the fixed frequency f of the generator.

резонатора, влияющим на начальное значение его собственной частоты

, может являться, в частности, какой-либо геометрический параметр оконечной нагрузки резонатора или (и) электрофизический параметр вещества, находящегося в электромагнитном поле этой оконечной нагрузки, а также совокупность указанных параметров. Для волноводного резонатора с колебаниями волноводных типов H_mnp или E_mnp известны и применяются реактивные компоненты, в частности диафрагмы емкостного и индуктивного типа в волноводах (Семенов Н.А. Техническая электродинамика. М.: Связь. 1973. С. 334-340). Такая реактивная компонента может быть в данном случае оконечной нагрузкой волноводного резонатора, ей можно управлять и изменять, тем самым, значение

.When measuring using a waveguide resonator (a long line segment, a volume waveguide resonator, etc.), a variable parameter

resonator affecting the initial value of its natural frequency

, may be, in particular, some geometric parameter of the final load of the resonator or (and) the electrophysical parameter of a substance located in the electromagnetic field of this final load, as well as a combination of these parameters. For a waveguide resonator with oscillations of the waveguide types H _mnp or E _mnp, reactive components are known and used, in particular diaphragms of capacitive and inductive types in waveguides (Semenov N.A. Technical Electrodynamics. M .: Communication. 1973. P. 334-340). Such a reactive component can in this case be the final load of the waveguide resonator, it can be controlled and changed, thereby the value

.

и, следовательно, произвести изменение (частотную модуляцию) частоты

волноводного резонатора в соответствующих пределах [f_p1, f_p2]. В частности для волноводного резонатора в виде отрезка длинной линии с колебаниями типа ТЕМ в качестве такого модулятора может быть применена оконечная нагрузка в виде электрически управляемого сосредоточенного реактивного сопротивления Х_н - переменной индуктивности L или переменной емкости С. При этом, соответственно, Х_н=2πfL, Х_н=1/2πfC. Наличие на конце отрезка однородной длинной линии индуктивности L эквивалентно удлинению короткозамкнутого на конце отрезка длинной линии на величину

, а наличие емкости С - эквивалентно удлинению разомкнутого на конце отрезка длинной линии на величину

. В этих формулах с - скорость света, W - волновое (характеристическое) сопротивление длинной линии (Викторов В.А., Лункин Б.В., Совлуков А.С. Высокочастотный метод измерения неэлектрических величин. М.: Наука. 1978. С. 10-29, 42-50).However, it is simpler and more efficient to carry out electrically controlled adjustment within fixed limits [X _n1 , X _n2 ] values

and therefore make a change (frequency modulation) of the frequency

waveguide resonator within the corresponding limits [f _p1 , f _p2 ]. In particular, for a waveguide resonator in the form of a long line segment with TEM-type oscillations, a terminator in the form of an electrically controlled concentrated reactance X _{n of} variable inductance L or variable capacitance C can be used as such a modulator. In this case, respectively, X _n = 2πfL , X _n = 1 / 2πfC. The presence at the end of a segment of a uniform long line of inductance L is equivalent to the elongation of a short-circuit at the end of a segment of a long line by an amount

, and the presence of the capacitance C is equivalent to the elongation of the open line at the end of the long line segment by

. In these formulas, c is the speed of light, W is the wave (characteristic) resistance of a long line (Viktorov V.A., Lunkin B.V., Sovlukov A.S. High-frequency method for measuring non-electric quantities. M .: Nauka. 1978. P. 10-29, 42-50).

As a variable capacitance C, in particular, a diode with a controlled capacitance can be used - a varicap (Davydova N.S., Danyushevsky Yu.Z. Diode generators and amplifiers microwave. M.: Radio and communication. 1986. 184 s).

волноводного резонатора - отрезка длинной линии, можно при фиксированной частоте f генератора производить измерение площади S под соответствующей резонансной кривой и, следовательно, определить искомое значение х измеряемой физической величины.Therefore, changing the value of the terminal reactive load of the long line segment - inductance L within [L ₁ , L ₂ ] or capacitance C within [C ₁ , C ₂ ] corresponding to the limits [f _p1 , f _p2 ] of the frequency change

waveguide resonator - a segment of a long line, it is possible at a fixed frequency f of the generator to measure the area S under the corresponding resonance curve and, therefore, determine the desired value x of the measured physical quantity.

в диапазоне [Х_н1, Х_н2], соответствующем диапазону изменения начальной собственной частоты

резонатора в фиксированных пределах [f_p1, f_p2]:The parameter S represents the area under the amplitude-frequency characteristic - the resonance curve, i.e. the area covered by the values of the amplitude A when changing the value

in the range [X _n1 , X _n2 ] corresponding to the range of the initial natural frequency

resonator in a fixed range [f _p1 , f _p2 ]:

The range [X _n1 , X _n2 ] should correspond to the range of vibration frequencies [f _p1 , f _p2 ] excited in the resonator at a fixed frequency f of the generator.

(т.е. при некотором номинальном значении х₀ измеряемой физической величины х) реактивного сопротивления Х_н оконечной нагрузки 3 волноводного резонатора 1. Значение

изменяется в фиксированных пределах [Х_н1 и Х_н2] и зависит, в свою очередь, от, по меньшей мере, одного параметра а оконечной нагрузки резонатора, изменяющегося в фиксированных пределах [а₁, а₂] с применением функционального элемента 4. К выходу резонатора 1 подсоединена цепочка последовательно соединенных детектора 6, интегратора 7 и регистратора 8. В регистраторе 8 определяют получаемое на выходе интегратора 7 значение функции S, выражаемой формулой (1), при девиации значения

в пределах диапазона [X_н1, Х_н2]. Этот диапазон должен соответствовать пределам изменения значений [х₁, х₂] измеряемой физической величины x.In FIG. 2 shows a diagram of a device for implementing the proposed method. Here, the waveguide resonator 1 contains a waveguide 2, which has an end load 3 at the end. Using a generator 4, electromagnetic waves are excited in the waveguide resonator 1 at a fixed frequency f. Using functional element 5, the initial

(i.e., at a certain nominal value x _{0 of the} measured physical quantity x) reactance X _{n of the} final load 3 of the waveguide resonator 1. Value

varies within fixed limits [X _n1 and X _n2 ] and depends, in turn, on at least one parameter a of the final load of the resonator, changing within fixed limits [a ₁ , a ₂ ] with the use of functional element 4. To the output resonator 1 is connected to a series of series-connected detector 6, integrator 7 and registrar 8. In the registrar 8 determine the value of the function S obtained at the output of integrator 7, expressed by formula (1), when the value deviates

within the range [X _n1 , X _n2 ]. This range should correspond to the limits of variation of the values [x ₁ , x ₂ ] of the measured physical quantity x.

Thus, this method of measuring a physical quantity is characterized by a simplification of the measurement process using a waveguide resonator by measuring the area under the amplitude-frequency characteristic at a fixed frequency with a change in the initial natural frequency of the resonator within fixed limits due to a change in the initial value of the final reactive load of the resonator.

Claims (1)

A method of measuring a physical quantity in which oscillations in the resonator are excited at a fixed frequency, when the initial natural frequency of the resonator is changed within fixed limits

determine its amplitude-frequency characteristic, calculate the area under it, which is used to judge the value of the measured physical quantity, characterized in that the resonator used is a waveguide resonator with an end load with reactance X _n , the area under the amplitude-frequency characteristic is found according to the relation

Where X _H0 - starting at the nominal value of the measured physical quantity, the value X _n, [X _H1, X _H2] - fixed limits change X _H0 corresponding fixed limits

, A (X _н0 ) is the amplitude of oscillations in the waveguide resonator at a value of Х _{н0 of the} final load.

Images