SU1506372A1 - Method of indicating resonance frequency of measuring circuit - Google Patents

Abstract

The invention relates to a measurement technique and makes it possible to increase the accuracy of the indication of the resonant frequency. According to the method, the high-frequency signal (C) of the resonant frequency is multiplied with a low-frequency C, the value of which is chosen equal to the half-width of the resonant curve between the points of maximum slope of this curve. Then, harmonic C of the sum and difference frequencies are extracted from the multiplied signals and sum the selected signals. The total C that has passed through the resonant circuit is multiplied alternately with the harmonic C of the total and difference frequencies. Harmonic C with a doubled value of the resonant frequency is selected, and the amplitudes of the selected C are equalized by changing the reactive parameter of the resonant circuit. 1 il.

Description

The invention relates to a measurement technique and can be used to indicate a resonant frequency while monitoring high quality sensors.

The purpose of the invention is to improve the accuracy of the indication of the resonant frequency.

The drawing shows a block diagram of a device for implementing the proposed method.

The high-frequency signal of the resonance frequency is multiplied with a low-frequency signal, the value of which is chosen equal to the half-width of the resonance curve between the points of maximum slope of this curve,

From the multiplied signals, the harmonic signals of the sum and difference frequencies are selected and summarized the signals. The total signal passed through the resonant circuit is multiplied alternately with the harmonic signals of the sum and difference frequencies.

Harmonic signals with a double resonance frequency are extracted.

The amplitudes of the allocated signals are equalized by changing the reactive parameter of the resonant pepe.

The casting of the proposed method from the known ones consists in the sequence of performing new signals operations with signals, as a result of which the accuracy of measurement of the reactive parameters of the sensors and their small changes is repeated.

The essence of the method lies in the T11z trace.

ate

about

bi with j

N5

The high-frequency signal of the re-frequency frequency U, (t) (b), + t + 4 i) is multiplied with the low-frequency signal U, Ct) - (: 2t + tfz). The value of the low frequency Q is chosen equal to the half of the bandwidth of the DY resonance curve at the level corresponding to the points of the maximal minimum slope of the Hi-i resonant curve of the measuring

chains,

. e. a l o / 2.

As a result of multiplication, an amplitude-modulated oscillation is formed with the suppressed carrier signal at the resonant frequency of the image.

, -n) tU3 (t) - | U, U ,, cos (CO, -IR, -LP, and- cos (co, + n) t + H.- -H 2b

where S (is the slope of the transformation,

It was equal to the difference frequency Q., CO | - C2. represents the signal of the lower side frequency of the resonance curve, and the component of the sum frequency tO CO, + O. is the signal of the upper side frequency,

From the two-frequency signal Uj (t), the harmonic signals of the difference and frequency frequencies are separated.

U, (t) - | - K, U ,,, U, cos (Wjt + (f ,,);

Uc (t) -2- .U costo t + Q, + g, -q 4),

where K and K are the Liltration coefficients at the frequencies Ci and COj, respectively;

- Rz, Lf 4 additional phase, the shifts brought at

filtering.

Sum the selected signals Uq. (T) and Uf (t-), to form again the two-frequency signal of the lower and upper side frequencies of the form

and

, (t) - - | ku, U, K, cos (W, t + lf5) - + K ,, cosCU, t Lfg),

gdvsr., q, -Cf,

Б b - phase shifts introduced after the cy t-vibration of U4 (t--) and UgCt oscillations,

A measuring circuit containing the successively connected capacitance C and the inductance L is simultaneously transmitted by signals from two side frequencies, C, and the signals from H1 and the upper frequencies pass through the circuit with a certain amount. OS-Pl. Pgtenia relative to the level of attenuation on the resonant frequency oo

p-1 1 /., to form a species

U, (t) - | - U ,,,, K, cos (u, t: + + C | 5 + tfr) + K, (CO, t: + lpg + fd),

where k

TO,

and K

To with

  .

the attenuation coefficients of the sig 1alop of the CO. frequencies, and the CO, respectively, 1;

Kp is the transmission coefficient of the transfer of a 1-dimensional circuit at a resonant frequency of COO «,;

Q 0) ,, / UCJ- is equivalent to the quality factor of the tsegti;

0);

WITH

with

iJJi (.6 W,

p and A, G-

OJn2iСъ

 from

wearable detuning;

ilf.j arctgQ T, and Cpj arctg phase shifts introduced by a circuit disturbed with respect to resonance,

Through the resonant circuit, the signal I (t) is multiplied alternately with the harmonic signals of the side frequencies, as a result of the multiplication of the signal 1) 7 (t) with the harmonic signal- / lanoM 11c. (t) bottom (delimit :) often s (multi-frequency signal of the form

and, (0 -4- ch to k ,,..

(2COit- -2Cpg + Lj,) + (+ 5 b -M,) + cos (2GJ, t + Cp5-Kp - q) g) j,

When the signal U (t) is multiplied with a harmonic signal UgCt) of the upper (with t-ball) frequency, a multi-frequency signal is formed

2

and ,, (1 :) g .os (2CO, t.) + K, (2gt + +, - ((J) + cos (2L: ,, t,).

From multi-frequency fishing Ug (t) and Ug (t), harmonic signals with a double resonance frequency of the form

Jt) ,, K ,, t +

+ q, + lf, + C; g + tf,);

u, (t)

, +

 5 + F7 +.),

where K is the coefficient t (b. gltracin nl frequency 2) ,; Wed - F ov; th shift introduced scht:

filtering

Compare amplitudes: - l; elloin jx signals and get pp. Night Escape

II

-5-- I,

K,)

sis.

G Y GK K.-J - P

 P1. one

-Jli- Q .r) (1 + Q L;)

Equalize -11vapt at-tplituda srvnivivpsm: p-: signals by changing the reactive PL-RamR-tra measuring system. R as a result of grinding capacitance C or inductance L And the resonant frequency 1 Deggy O ;, 1 A | LC changes, and, consequently, the relative detunings of the circuits Ti change, and L2 „If the amplitudes are equal, compare the Eq. equal (l,)), and the numerator in the expression for differential difference is equal to (zero). From the equality of the absolute values of the relative detunings it follows that

  .

Chow, -and

 Wt + QGO,

/ A, 1

COj H - Wo /

 COOS, + S2o

from where have

C0 „

The device contains a high-frequency generator 1 CO, a nerve multiplies a fir-tree 2 a balanced modulator, a low-frequency generator 3, band-pass filters and 5 difference and sum frequencies, day 6. 6. first automatic switch 7, l. Selector 8 frequencies sequentially connected inductance 9 and capacitive sensor 0, forming a measuring cell)

chain, varihon 11, priv p; resistor

063726

oggeratsion} 1st amplifier 13, second re-; pistol 14, second multiplier 15 (balanced mixer) selective g amplifier 16 at double the frequency, amplitude detector 17, second automatic switch 18, third resistor 19, first capacitor 20, 10 fourth resistor 21, second capacitor 22, differential amplifier 23 and indicator 2A,

-

;)

-: one

35

,

The device works as follows

As a result of multiplying the siphalop generators I and 3, in the balanced modulator oscillations of the difference and sum frequencies are formed, which are separated by filters 4 and 5 and connected again into one signal by the adder 6. CiT iMapHMe oscillations excite a continuous sequence; then measuring circuit 9 and 10 on two

2 side frequencies. Amplifier 13, whose input impedance, due to parallel negative feedback through resistors 12 and 14, is close to zero, converts the two30 resonance frequency current into a proportional voltage. This is the same as multiplying. in the balanced mixer 15 alternately with the signals of the side frequencies, we supply1) 1x through the first automatic switch 7. From the resulting signal, a voltage amplifier with a double oscillator frequency 1 equal to half the control voltage of the switch 7 is amplified and amplified by the selective amplifier 16. Period the commutation switch 7 is set by the divider 8 frequency and is selected 10-20 times longer than the period of the low-frequency signal of the generator 3. The amplified packets of the double frequency voltage alternately rectify ml one detector 17 and separated by a second auto-

50 Matical switch 18, operating synchronously with switch 7, Straightened voltages smooth out-: averaging chains 19.20 and 21.22 and go to the differential (}) 55 55 P1 1st amplifier 23. Amplifier 1 H1 differential voltage c the output of the amplifier 23 changes the capacitance of the varicap 11 in the direction of the convergence of the resonant frequency of circuit 9 and 10 with the frequency of generator 1. The voltage of the voltage of the following system of the resonant circuit is indicated and recorded by a self-recording device 2A,

Claims (1)

Owing to the indication of the resonant frequency, the accuracy of measuring the relative deviations of the capacitance of the overlay sensors with an initial capacitance of 1–30 pF and limits of 10 ± 10 with an error of no more than 0.5–1% at frequencies of 5–10 MHz is increased. Formula of the invention) 1i The method of measuring the resonant frequency of the measuring value, based on the formation of the test signal in the form of the sum of two components whose frequencies are mixed relative to the resonant frequency of the measuring circuit. Half of its flow rate was excited by the test signal of the measuring value, separated from its output signal signal of two oscillations and comparing the amplitudes of these oscillations, I distinguish With this modulation, Lorm 1 ammunition moduli1) an oscillation with a modular frequency equal to half the measuring bandwidth of the measuring circuit, 1m total and difference frequency oscillations adjacent to the resonant frequency of the measuring circuit are separated out of it, and from the forms 1 test signal: g p the sum of the oscillations O mmar and the difference frequency, which M excites the measuring circuit, then the output signal of the measuring circuit is not combined with the component of the test signal of the total frequencies (extended from the 0 GH signal of the signal double the resonance with the pstote, and then the output signal of the measuring scale is multiplied from the component test signal of the discriminating frequency) and the oscillation with the double resonance frequency is extracted from the resulting signal, after which a JJ of the two oscillations compare double the resonant frequency and the indicator from the resonant frequency with equal amplitudes compared. neither .The composer L "Muranov 1 edaktor L Kozoriz Tehred I. lodanichKorrektor V.KaOats 1Y Order 5D31 / 47 Circulation 714 V11ISH1I of the State Committee for Inventions and Discoveries at the State Committee on Labor and Defense of the USSR 113035, Moscow, Zh-35, Ra Paska Emb., 4/5 Subscription