SU842632A1 - Device for measuring resonance circuit q-factor - Google Patents

Description

This invention relates to a measurement technique, in particular, to measuring the quality factor of a resonant circuit. The known method and device for measuring the quality factor, based on the shock excitation of the measuring circuit using a pulse generator, enhancing the response and counting periods of damped oscillations, the amplitude of which is less than the specified level of the beginning of the account, but greater than the specified level of the account. A device for carrying out this method comprises a pulse generator amplifier with automatic gain control, a threshold device, a key, a meter with an indicator. The closest to the technical essence of the invention are a method and a device according to which shock excitation is performed by a circuit capacitor. charged from a source of constant voltage. Crit {zazr de contour capacitor reads the number of damped oscillations in the measuring circuit, the amplitude of which is less than a given level of the beginning of the account, but more than a given level of the counting wave, and, moreover, the ratio У2 is equal to е. -, n - the number of oscillations when the level changes from to C.T.e. direct reading of the value of the quality factor is possible. To improve the accuracy, a series of measurements (10 or 100) is carried out and their results are averaged. This device contains a stabilized power supply, the output of which is connected to a loop capacitor through a switch and simultaneously through a voltage divider to one of the inputs of the comparison circuit, to the other input of which the circuit under study is connected via a switch and its output is connected to a serially connected switch frequency, counter and digital indicator 2 The disadvantage of the known device is that with an increase in the frequency at which the measurement of the quality factor is made, the level of the counting reduced, which causes increase in the relative instability threshold device 1oschego determines the ending time of counting the number of oscillations as a result of which the quality factor measurement error increases. Increasing the counting start level by simply increasing the excitation pulse also results in an age error in measuring the quality factor due to the nonlinearity of the magnetic core of the loop inductance. Averaging the results of several measurements gives a decrease in the error due only to a short-term instability of the device response threshold.

The purpose of the invention is to improve the accuracy of measuring the quality factor of the resonant circuit at high frequencies.

The goal is achieved in that a device for measuring the Q factor of a resonant circuit contains a stabilized power source, the output of which is connected via a switch to the resonant circuit and to one of the inputs of the comparator, and through a voltage divider to another input of the comparator, the output of which is connected a key, a frequency divider, a counter and a digital indicator are connected in series, a generator, an additional key, a counter with a controlled counting coefficient, a code definition block set The generator’s output is connected to the inputs of an additional key and counter with a controlled counting factor, the output of the latter is connected to the control inputs of a key and an additional key, the output of which is connected to the control input of the switch, and the output of the counter is connected to the control inputs of the frequency divider, a counter with a controlled counting factor, and a voltage divider.

The drawing shows the functional electrical circuit of the device for measuring the quality factor.

A device for measuring the quality factor of a resonant circuit, which has two measurement limits (15-50 and 50-500), contains a stabilized power source 1, the output of which is simultaneously connected via switch 2 to a capacitor 3 of the resonant circuit 4 being connected, connected to one of the inputs of the comparison unit 5 and, through a voltage divider 6, made with a variable factor, to another input of the comparison unit 5, the output of which is connected to a series-connected key 7, a frequency divider 8, a counter 9. and a digital indicator 10; The generator 11, which controls, via a control key 12 to Imitator 2, is also connected to one of the inputs 13 of the counter with a control of the counting coefficient connected to the key. 7. and an additional key 12; the counter 9 is connected to a block 14 for determining a code of a given number, the output of which is simultaneously connected to the control inputs of voltage divider 6, frequency divider 8 and counter 1 with a controlled counting factor.

The device works as follows.

When the discharge of the loop capacitor 3, pre-charged from the power source 1, in the resonant one. Loop 4 causes damped oscillations. Comparison unit 5 generates pulses until the oscillation amplitude is less than U, the value of which is determined by the voltage divider b. Let at the first measurement and. The generated pulses are counted by the counter 9. Since the switch 2 is controlled by the pulses of the generator 11, the shock excitation

repeats until the additional key 12 closes, which occurs after two pulses are recorded in the counter 13 with a controlled counting factor. At the end of the counting of pulses after the second cycle of shock excitation, the block 14 for determining the code of a given number determines the number recorded in the counter 9. If it is less than 50, then the division factor of the divider δ (the voltage U at the same time becomes equal to j-) and the coefficient of the debt Jt

This 13 meter counter is controlled by a lm by two to five counting coefficient, and also a frequency divider 8 is connected by four and the measurement is repeated. If the number recorded in the counter 9 is greater than 50, it is displayed on the indicator 10.

Thus, the choice of the limits U and and from the condition of the minimum error and, use the expression

and"

Un p Un

AUn

) p- ti- ug

0-0

en (iLn-.

Jt

-J.

and/

and

about

where U (j - level of the beginning of the account;

UI, the level of termination of the account; Q - the quality factor of the resonance con

tour.

This makes it possible to reduce the measurement error by no less than 2 times (for large values of Q), and the gain in obtaining the minimum error increases significantly with increasing relative instability di

lime uo

which corresponds to the measurement conditions in the high-frequency part of the range.

Claims (2)

Invention Formula A device for measuring the quality factor of a resonant circuit contains a stabilized power source whose output through a switch is connected to a resonant circuit and to one of the inputs of the comparison unit and through a voltage divider to another input of the comparison unit whose output is connected to serially connected switches; , a counter and a digital indicator, characterized in that in order to improve the accuracy of measuring the Q-factor and the resonant circuit at high frequencies, a generator, an additional a key, a counter with a controlled counting coefficient, a code for determining a given number, the generator output is connected to the inputs of an additional key and a counter with a controlled account coefficient, the output of the latter is connected to the control inputs of the key and an additional key, the output of which is connected to the control input of the switch, and the output of the counter is connected to the control inputs of the frequency divider, a counter with a controlled counting coefficient, and a voltage divider through the code definition block. Sources of information taken into account during the examination 1. A. A. Grokholsky. Q Meters - Numeters. Novosibirsk, Science, 1966. 2. The author's certificate of the USSR 180656, cl. G 01 R 27/26, 1966 (prototype).