SU1132249A1 - Device for measuring frequency difference - Google Patents

Abstract

DEVICE FOR. MEASUREMENT OF THE DIFFERENCE OF FREQUENCIES according to author. 974290, that is, so that, in order to increase speed, a two-pole controlled driver-limiter and a summing amplifier, connected between the output of the controlled voltage-limiter and the first output of the isolation the capacitor to the second input of the summing amplifier is connected to the output of a two-pole controlled driver limiter, the first and second inputs of which are connected respectively to the first and second outputs of the difference frequency pulse extraction unit, and yuschy input - with the output of the transducer length. period to voltage. (L cz

Description

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S1 Invention relates to electrical measuring equipment and can be used as a measurer of the relative frequency difference or a measurer of the relative difference in speeds, for example, the rotation of various mechanisms equipped with frequency sensors that convert the speed to the iroportional frequency of the pulses. According to the main auth. No. 974290, a device for measuring the frequency difference is known, which contains input pulse shapers, a differential frequency pulse extraction unit, the outputs of which are connected to the inputs of differential frequency current pulse shapers, a coupling capacitor, a filter, connected to a current meter, for example, an operational amplifier with a dial gauge, Phase-to-duty ratio transducer, higher frequency selection unit, transducer of period duration to voltage, controlled voltage-limiter, the inputs of the phase difference converter to the duty cycle are connected respectively to the outputs of the two input pulse drivers and to the inputs of the differential frequency pulse selection unit, and the output is connected to the input of a controlled voltage limiter, the control input of which is connected to the output of the period duration in voltage circuit The input is connected to the output of the higher frequency selection block, whose inputs are connected to the outputs of the input pulse shapers, the second output of the separator condensate ra connected to the input filter and the output of the difference-frequency current igotulsov disadvantage of the known device is the low speed due to insufficient compensation of the difference frequency pulsations in the output signal SG. Pulsations of the difference frequency result in the appearance of a dynamic error, in order to reduce which it is necessary to increase the filter time constant, which quickly reduces the operation of the device. The purpose of the invention is to enhance. the speed of the device 49I due to the co-sensation of the pulsations of the difference frequency in the output signal. The goal is achieved by introducing a two-pole controlled driver limiting device and a summing amplifier connected between the output of the controlled voltage limiter and the first output of an isolating capacitor, the second input of the summing amplifier is connected to the output of the two-controlled controlled voltage driver, the first and the second inputs of which are connected respectively to the first and second outputs of the differential frequency pulse extraction unit, and the control input to the output p eobrazovatel period duration in voltage. Figure 1 shows a block diagram of a device for measuring the frequency difference; in fig. 2 is one example of a specific implementation of a bipolar controlled limiter; FIG. 3 shows stress graphs that show the operation of the device. The device contains input shapers 1 and 2 pulses, a differential-frequency pulse extraction unit 3, shapers of a differential frequency pulse shaper 4 and 5, a phase difference-to-duty ratio converter 6, a higher frequency selection unit 7, a period-to-voltage converter 8 controlled by the driver o; - voltage suppressor 9, separation capacitor 10, filter 1 b, current meter 12 ,. For example, an operational amplifier with a switch device, a two-pole controlled driver-limiter 13 and a summing amplifier 14. The outputs of the input drivers 1 and 2 pulses are connected to the corresponding inputs of the differential-frequency pulse extractor 3, the phase difference to duty cycle converter 6 and the higher frequency selection unit 7 , the outputs of the block 3 of the differential-frequency pulse pulses are connected to the corresponding inputs of the formers 4 and 5 pulses of the differential frequency and to the first and second inputs of the two-pole control Limiter 13, the control input of which is connected to the output of the converter 8, the period duration is voltage, and the output is connected to the second input of the summing amplifier 14, the first input of the latter is connected to the output of the controlled voltage limiter 9, the first input which is connected to the output of the converter 6 phase difference in the duty cycle, and the second control input to the output of the converter 8 of the period duration to voltage, the input of the latter is connected to the output of the high frequency selection unit 7, STUDIO 4 and 5 the difference frequency pulses are connected through a filter 11 to the input of a current meter 12, and also via a capacitor 10 to the output of the summing amplifier 14, the output current meter 12 is. output, device. The current meter 12 is an operational amplifier 15 covered by negative feedback (resistor 1 b, the output of the operational amplifier 15 is the output of current meter 12 and connected to a switch device 17. The dual-driver limiter 13 of FIG. 2) can be post royen on keys 18 and 19, amplifier 2 inverter 21, resistors 22-26. The Converter 6 of the phase difference in the duty cycle can be made in the form of RS-trigger, triggered by the inputs of pulses from the input drivers. The difference frequency pulse extracting unit 3 may be implemented using known circuits, extracting a higher frequency pulse to the slender one, which came again in a period of a lower frequency. Shapes 4 and 5 Differential frequency impulses can be made as stable current generators on operational amplifiers. The converter of the duration of the period to the voltage can be performed according to any known scheme of the integral of the storage device, where the input current is set constant, and the integration time is set equal to or proportional to the duration of the period of the higher frequency. The higher frequency selection unit 7 can be performed, for example, in the form of an RS flip-flop, to the inputs of which differential frequency pulses are applied, and the outputs control the keys to the informational inputs of which the input frequencies f and fj are fed respectively. The device works as follows. The sequences of input frequency pulses formed by the shaper 1 and 2 are fed to the inputs of the differential frequency extracting unit 3, to the inputs of the converter 6 phase difference in the duty cycle and to the inputs of the higher frequency selection unit 7. Differential frequency pulses from the output of block 3 are fed to Bx.optd of 4 or 5 pulse formers of a differential frequency current and to the inputs of a two-pole graf-head reader 13. At the output of shaper 4 or 5, differential pulses of Ka.tEjj are formed (Fig.3 &) and go through the filter 11 to the input of the current meter 12, creating in it the average current value, proportional to the relative frequency difference 1 oIi-3 idi: T „- ° T-P -r where T is the period of the difference frequency; T is the duration of the conversion period. The pulse sequence from the output of the higher frequency selection unit 7 is fed to the input of the converter 8, the period duration into a voltage that forms a constant voltage proportional to the period duration of the larger of the two frequencies. This voltage is fed to the control inputs of the controlled shaper limiter 9 and the two-pole shaper limiter 13. The other input of the controlled shaper limiter 9 receives from the converter 6 a pulse sequence, the duty cycle of which is determined by the phase difference of the input frequency pulses. At the output of the controlled limiter 9, a sequence of variable duty cycle pulses is formed with an amplitude t (nepepadok) equal to twice the output voltage of the converter 8. At the output of the controlled twopolar limiter I3, S is formed. voltage difference pulses with an amplitude equal to the output voltage of the converter 8, t equal to half the amplitude of the variable duty cycle pulses of the limiter 9. The pulses from the outputs of the limiter 9 and the two polar limiter 13 are fed to the sum amplifier 14 the output of which is formed by the total voltage f (32). This signal arriving through the separation capacitor Yu to the INPUT: filter 11 does not carry an average value - the current is due to the presence of the separation capacitor, but its harmonic components are almost phase-phased harmonic composition of the signal of the driver 5 carrying the average current (Fig.38). ). The appropriate choice of the output voltage of the converter 8 for the duration of the period to voltage, i.e. T, selection of the scale in accordance with the expression q 2UC 1pT2, ensures equality of the charges transmitted through the coupling condenser: pp 10 by the pulses from the output of summing amplifier 14, and differential frequency current pulses with formers 5, i.e. almost full compensation of differential frequency pulsations in the output signal is provided. Pulse III and differential frequency in the output signal are determined by the nonidentity of the pulse shape supplied through the separation (dosages) capacitor and from the differential frequency current pulse generator. Moreover, for a small frequency difference (Tj Tr), the amplitude of the pulsation of the first harmonic of the difference frequency is determined mainly by the shift of the centers of gravity of these pulses. The voltage at the input of the filter 11 (Fig. 3 is formed by current pulses of the difference frequency IQ (Fig.3 &)) carrying charge H, and voltage pulses supplied through the separation capacitor from the output of summing amplifier 14 (FIG. 3 At the inputs of the amplifier summation pulses of variable duty cycle amplitude 2U, carrying on each front charge q, and voltage pulses 49 with amplitude U (Fig. 38), carrying a charge of + -§- on the leading edge of the pulse and -: on the falling front of the pulse. these charges are shifted by ria T - ii T,. T, "t, Cfa ± p4-t-: f7 angle 0, + /.)- - --- relative to impulses qs q, which, in turn, is shifted by the angle tfg with respect to the charge i and | q, t Uil q. The total relative ripple of the difference frequency is determined by the geometric sum of the vectors H, i, and is equal to:,, ein2q.,: - ..., -. Considering that U 1, and decomposition. "SinCfuCf i-, we get in fig.Za The waveform at the input of the current meter is shown. Thus, the ripple-difference frequency in the proposed device ...... t: -,. ve is less than in If. 2 prototype. (-1 .., oo) For example, when -p- 0.01, the difference frequency pulsations are 60 times less than in the prototype. The substantial reduction of the pulsations reduces the time constants of the filter links, which directly leads to a decrease in the delay in the measurement channel of the difference frequency, i.e. to increase the speed of the device. The bipolar driver-limiter 13 ((fig. 2) p, works,; as follows;;, In the absence of impulses, the difference frequency (fp, fpw) key 18 is open, key 19 is closed, i ap ation at point A and on the invert and non-inverting inputs of the amplifier 20 is equal to Uex 12 at the same time, the voltage at the output of Uftt ,, 6. At the appearance of a differential frequency pulse, the key 19 is disconnected, and the voltage at the output of the amplifier

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Thus, the proposed device has high speed by reducing the difference frequency ripples in the output signal.

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Claims (1)

DEVICE FOR MEASURING THE DIFFERENCE OF FREQUENCIES according to ed. No. 974290, with the exception that, in order to improve performance, a bipolar controlled shaper-limiter and a summing amplifier are included in it, which is connected between the output of the controlled voltage shaper-limiter and the first output of the isolation capacitor, the output of the bipolar controlled shaper-limiter is connected to the second input of the summing amplifier, the first and second inputs of which are connected respectively to the first and second outputs of the differential frequency pulse extraction unit, and controlling th input - with the output of the duration converter. period in tension. ,