SU1374146A1 - Device for determining parameters of oscillatory circuits - Google Patents

Abstract

The invention relates to a radio measuring technique and allows to increase the accuracy of measuring the quality factor of oscillatory circuits (K) and reactivities of low Q. The device contains an excitation voltage generator 1, an automatic adjustment unit 5, a detector 5, a measurement unit 7, a communication element , K 9 and a voltmeter 10. A phase detector 3 is introduced into the device, the inputs of which receive a voltage and a and d from the generator 1 and the measuring unit 7. The output voltage is U, Ucosi /, where (f is the phase angle between voltage by mi and and j., is fed to the subtracting unit 6, where the supplied voltage Ug detector 5. The resulting differential voltage is equal to U U cosif- Uj. oscillating circuit parameters determined from the expressions presented in the description text. 1 yl. (A

Description

with

four

41 O)

The invention relates to the field of radio metering technology and can be used to measure the quality factor, loss tangent of dielectrics, active resistance, capacitance and inductance.

The aim of the invention is to improve the accuracy of measuring the Q-factor of high-quality oscillatory circuits and reactivities of low-Q oscillatory circuits.

The drawing is. block diagram of the device for determining the parameters of oscillatory circuits. The device circuit contains a generator of excitation voltage 1, a resistor 2, a phase detector 3, an automatic adjustment unit 4, a detector 5, a subtraction unit 6 ,. measuring unit 7, coupling element 8, oscillating circuit 9, voltmeter 10.

Moreover, resistor 2 and the first input of the phase detector 3 are connected to the output of the exciting voltage generator 1, and the control input is connected to the output of the automatic adjustment unit 4, the input of which is connected to the output of the detector 5 and to the first input of the subtracting unit 6, the second input which is connected to the output of the phase detector 3. The second terminal of the resistor 2 is connected to the input of the detector 5, to the second input of the phase detector 3 and to the input of the measuring unit 7 containing the series-connected communication element 8 and the measuring oscillating circuit 9. In The output of subtraction unit 6 is connected to a voltmeter 10.

A device for determining the parameters of the oscillating circuits works as follows.

The excitation voltage with a given frequency from the output of the generator 1 through the resistor 2 and the coupling element 8 enters the measuring oscillator circuit 9. When tuning the oscillatory circuit 9 in resonance at the frequency of the excitation voltage using a reference reactive element (in particular, the measuring capacitor) The input impedance of the measuring unit 7 In this case, the input impedance of the measuring unit contains the active R and reactive X components.

The active component of the input impedance of the measuring unit is determined by the active power consumed by the measuring oscillating circuit, i.e.

,five

(one)

, 2

H

and

RBK

where i C current in the oscillatory circuit; t active resistance

oscillatory circuit in sequential replacement; Uj, is the input voltage of the measuring unit 7;

6U is active component of the input impedance of the measuring unit 7. Given that

Ujx- n

one

rfT

+ a

and Q Qc / C;

one

Loolc

w -c - g

(2)

(3) (4).

where Q is the quality factor of the oscillatory contour; i) g is the specified angular frequency of the exciting voltage; Cjj, Lp - respectively

capacitance and inductance of the oscillating circuit at resonance; n - coupling coefficient of the oscillating circuit 9 s

an external circuit through the communication element 8; GHS - relative detuning

oscillatory circuit capacity;

from expressions (1) and (4) we get

(-) 1:;: yb

 ()

(five)

At resonance and

one

 in

P

 U) oLo ff-

u, C, n q -

From expressions (5) and (6) it is clear that

the value of the active component R

5X

The input impedance of the measuring unit 7 with known values of w, n, C (or LO) gives full information on the quality factor and g, L, C - parameters of the investigated oscillatory circuit.

The measurement of the active component of the input impedance of the measuring unit 7 is performed as follows. The first input of the phase detector 3 receives the voltage U from the output of the generator 1, and the second input receives the voltage U from the input of the measuring unit 7.

In this case, the voltage U is kept constant by means of the automatic output control unit 4 and is the reference voltage for the detector 3.

As a result, the output of the phase detector 3 is a voltage determined by the expression

razheny (5), (6) (8) and (11) is determined by the maximum value of the differential voltage U, obtained at the output of the subtraction unit 6 (i.e. the maximum voltmeter 10) According to the known values to, Cf ( or b), and, R and Ugy define the parameters of the oscillating circuit:

ten

(12)

15

and U cosg-,

(7)

where Lf is the phase angle between eg

wives and and and,

which is fed to the first input of block 6 subtraction. The second input of the subtraction unit 6 is supplied with a voltage from the output of the detector 5, the value of which is equal to Ug.

In this case, at the output of the subtractor, a difference value of voltage is obtained, equal to

and cos if - Xex

(8) (9)

Where

(ten)

As a result, from expressions (8) - (10)

R. R-5- 01) The moment of resonance of the measuring oscillating circuit according to you

five

0

five

0

Claims (1)

Formula Fig. E. A device for determining the parameters of oscillatory circuits, containing an excitation voltage generator, as well as a detector and measuring unit connected by its inputs, an automatic output control unit, the input of which is connected to the detector output, and the output voltage to the control input of the exciting voltage generator, and A voltmeter, characterized in that, in order to improve the measurement accuracy, a resistor, a phase detector and a subtraction unit are inserted into it, and the output of the exciting voltage generator is connected through a resistor the input of the measuring unit, the first input of the phase detector is connected to the generator output of the exciting voltage, the second input to the input of the measuring unit, and the output to the first input of the reading unit, the second input of which is connected to the output of the detector, and the output to the voltmeter input .