SU654915A1 - Meter of frequency errors of voltage dividers - Google Patents

Description

This invention relates to the field of electrical measurements. A device for measuring the non-uniformity of the frequency characteristics is known, in which the reference and test signals at the output of the circuit 1 are periodically compared. separated by the studied circuit, the integrator and the null indicator 2. The unevenness of the frequency response is determined by the formula A- (w) - / f (0) m. t (o): -i5L-Z ::: | l- (O) where TI and T2 are the durations of the breaker switching intervals. The disadvantages of such devices include low accuracy and a limited range of frequency measurements. The purpose of the invention is to improve the accuracy of measurements in a wide frequency band. To do this, a meter that contains a harmonic signal generator, an integrator, the output of which is connected to the input of a null indicator and a rectifier, whose input is connected to the output of the first automatic switch and the output to the input of the second automatic switch, the first output of which is connected to the integrator input and the second} input of the first automatic switch, and its second output is connected to the first input of the first automatic switch, with the control inputs of the first and second automatic switches connecting cheny to the generator output switching pulses controlled duration and to the input of the switching pulse meter, put the second harmonic signal generator, two balanced mixer, the matching stage, a selective amplifier, the third switch circuit, the switch and the filter of the upper and lower frequencies. In this case, the corresponding inputs of the first balanced mixer are connected to the outputs of the first and second harmonic signal generators, and its output to the input of the switch, the first output of which is connected to the input terminal, and the second output to the output terminal of the voltage divider, through parallel-connected high and low pass filters connected to the corresponding inputs of the third automatic switch, the control input connected to the output of the switching pulse generator s adjustable duration. The output of the third automatic switch is connected to the input of the second balanced mixer, the second input of which is connected to the output of the first generator, and its output through a selective amplifier with the first input of the first automatic switch. The drawing shows the functional diagram of the device. It contains generators 1 and 2 harmonic signals, balanced mixer 3, switch 4, object under study 5, matching stage 6, low pass filter 7, high pass filter 8, automatic switch 9, balanced mixer 10, selective amplifier 11, automatic switch 12, switching rectifier 13, automatic switch 14, integrator 15, zero-indicator 16, generator of 17 switching pulses of adjustable duration, meter 18 of the duration of switching pulses. In the mixer 3, the voltage of the generator 1 is the frequency coi and, (t) - and cos. multiplied by the harmonic signal of the generator 2 frequency 02; 7j (t) cos toj. The output of the mixer 3 is the voltage t /, (. COs ((o, - ",) + +, fy, COS (", +),) And where k is the transfer coefficient of the mixer dimension (1 / V). As The reference signal uses the difference frequency i-02 0) 2 - const. The constancy of the frequency of sho is achieved by appropriate selection of the frequencies of COi and CU2. The sum frequency component is used as the test signal. The amplitudes of the reference and test signals are equal and are determined by the product. The measurement process consists of two stages. At the first stage, the measurement path is calibrated. In the "Calibration" mode, the transmission coefficient is equalized, respectively, to the measuring path, which does not contain the object under study 5, at the reference frequency "O" and one of the test frequencies with. Switch 4 closes the contact a. Automatic switches 9, 12, 14 operate in a symmetric mode (0.5 / K). The operation mode of the switches, symmetric or asymmetrical (ti ± ± T2), is determined by the duration of the control signals generated by the device 17. The device 17 generates switching pulses with a repetition period of k 1: 1 + 1: 2 const. The voltage from the output of the mixer 3 through the matching stage 6 enters the filters 7 and 8, which are tuned to the frequencies coo and w, respectively. Voltage frequencies coo and c are fed to the first input of the mixer 10 through the contacts of the automatic switch 9, and the second input of the mixer 10 receives the coi frequency signal from generator 1. At the output of the mixer 10 at different switching intervals, signals are generated that contain the harmonic of the same frequency 0) 2, which is allocated by the selective amplifier I. From the output of the amplifier AND the signals of the frequency 0) 2, the level of which is determined by the frequency response of the measuring path section from the output of mixer 3 to the reference frequency and the test frequency, through the contacts of the automatic switches 12, 14 and the rectifier 13 are fed to the input of the integrator 15. The balance of the amount of electricity on the accumulator element of the integrator 15 in the calibration mode, to one of the test frequencies, is achieved by proper adjustment of the transfer coefficients (tCoo) and / CsCto) filters 7 and 8 or one of them. The equality of the constant components at the output of the integrator is judged by the zero readings of the zero indicator 16. The achievement of equality of the switching intervals is monitored by the readings of the duration meter 18. As a result of the calibration, the transmission coefficients of the sections of the measuring path are equal from the output of the mixer 3 to the output of the rectifier 13 to the reference 0) 0 and one of the test frequencies ω, i.e. ((1) о К) Cs1 ((). test frequency calibration process is repeated. In the second stage, the relative frequency error of the object is measured 5. Switch 4 closes contact B. If the transfer coefficients of the object under study 5 at frequencies o and o are unequal, then the balance of the amount of electricity for you The integrator 15 installed at the calibration stage is violated. It is restored by changing the duration of the switching intervals TI and T2 by adjusting the duration of the switching pulses produced by the generator 17. The amplitude balance conditions in this case are written as: K) K) (( K ,,, ((dt,

where TI and T2 are switching intervals (m1 + T2);

/ C5 (®о) К K5 ((f) - transfer coefficients of the studied circuit 5 on the corresponding

frequencies; f

and (o) o) and (a) - t / io) a-amplitudes

reference and test signals.

Taking into account the equality of the amplitudes f / ((uo) and f / (co), after integration we obtain the ratio

/ H, K) A, J, K) tj- / Go (w) L ,,, (w) t ,.

Since the transmission coefficients of the channels of the reference and test frequencies are aligned at the calibration stage, the ratio

A.i. K) A:. ,, (O)) / g.,. K) / g. ,, (w).

Using the expression for the frequency irregularity of the object under study, we obtain the expression (1) in the form

// TsCta) -AsCa) Jti.

 A-5K)

The switching intervals TI and T2 are fixed using a standard meter 18 duration, which is connected to the output of the generator 17 switching pulses with adjustable duration.

The proposed device makes it possible to measure the frequency error of objects with an arbitrary type of connection between the input and output, to improve the accuracy and sensitivity of measurements in a wide frequency band.

Claims (2)

Invention Formula A frequency error meter of voltage dividers containing a harmonic signal generator, an integrator whose output is connected to the input of a null indicator, and a rectifier whose input is connected to the output of the first automatic switch and the output to the input of the second automatic switch, the first output of which is connected to the input of the integrator and to the second input of the first automatic switch, and its second output is connected to the first input of the first automatic switch; the control inputs of the first and second automatic switches are connected to the output of the switching commutator pulses of adjustable duration and to the input of a meter of the duration of switching pulses, characterized in that, in order to improve the measurement accuracy in a wide frequency band, a second harmonic generator, two balanced mixers, a matching stage, a selective amplifier, a third automatic switch, a switch and high and low pass filters the inputs of the first balanced mixer are connected to the outputs of the first and second harmonic signal generators, and their output is connected to the input of the switch, the first output of which is connected to the input terminal, and the second output to the output terminal of the voltage divider and the output of parallel-connected high and low pass filters are connected to the corresponding inputs of the third automatic switch, the control input of which is connected to the output of the switching pulse generator p Adjustable duration, and the output of the third automatic switch is connected to the input of the second balanced mixer, the second input of which is connected to the output of the first generator, and its output through a selective amplifier is connected to the first input of the first automatic switch. Sources of information taken into account during the examination 1. USSR Author's Certificate No. 359607, cl. G 01 R 23/20, 1969. 2. USSR author's certificate number 490026, cl. G 01 iR 27/02, 1974.