SU894607A1 - Sawtooth voltage non-linearity coefficient meter - Google Patents

Description

(54) MEASURING FACTOR OF NONLINEARITY COEFFICIENT

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The image refers to electrical measuring equipment, namely, the technique of measuring electrical parameters, and an automatic control of the non-linearity of the sweep voltage in television can be used, as well as to control the shape of sawtooth wave pulses used in other areas of radio electronic -. troniki and in nuclear electronics.

A device for measuring the non-linearity of a PN is known, in which a cathode-ray tube ll is used to determine the non-linearity coefficient (KN).

The drawback of the device is the low accuracy and complexity of the measurement process.

Closest to the proposed device for measuring the nonlinearity of the PN, based on its differentiation, characterized by low laboriousness of the measurement process, direct reading of the values and the sign of the CN, the possibility of promptly determining this parameter on

any selected area mon. The device contains a series-connected differentiating capacitance, an amplifier-limiter and a buffer cascade, two gating helmets oa, made in the form of serially-connected adjustable time delays connected to the source of clock pulses, two flippers of strobe pulses and keys, two peak detectors, and an analog circuit to calculate.

To tani, as well as a differentiating circuit connected in series, a peak detector, an integrator with a dongle switch switched from a source of clock speeds with a stable frequency, a comparator and a source of optical voltage G2.

The drawbacks of the device are, firstly, that the measurement result. The SC, due to the complexity of the comparator output pulses, depends on the voltage of the reference source and the parameters of the auxiliary PN, produced by the integrator (initial level of the PN, slope, nonlinearity of the repetition period). Variation

The values of these values under the action of teMneparypbi, humidity and other factors determine the measurement error of the VF,. The effect of absorption is especially significant when the storage capacity is quickly discharged through the key. Practice shows that when switching a capacitance of 0.15 µF through a discharge switch for 10 MKS, the error in determining the VF due to the absorption of a 78-P capacitor can reach several percent. The instability of the steepness of the PN is determined mainly by the variation of the storage tank. The accuracy of the change in capacitance for a temperature difference in an NFFZ of 2.5%. The nonlinearity of the PN in the case of using high-quality integrating circuits does not exceed one hundredth of a percent and its effect on the result of measuring the CN can be ignored. As for the error due to variations in the voltage of the reference source and the frequency of the clock pulse, when using thermocoupled zener diodes and a quartz oscillator, its value turns out to be negligible.

Secondly, the result of measuring a KN in a known device is represented by a constant voltage level, i.e. in analog form, which makes it difficult to quickly register and memorize for a more or less long period of time. The use of analog-ci (} rsky transducer for organizing a digital readout is irrational, since it complicates the design of the device and, in addition, introduces additional error in the determination of the VF.

Thirdly, the device has a large inertia. With a monitored PN of 20 ml, the time taken to establish one indication is approximately 5 seconds. The low speed is conditioned by the method of measuring KN, which assumes effective smoothing in the node of voltage pulses coming from the output of the modulator, in order to isolate their constant component. It can be considered that the time constant of the indicator damping device should be approximately 500–7 times the duration of the auxiliary TI formed by the integrator, i.e. Approximately 0.6-0.8 seconds.

The purpose of the invention is to improve the accuracy, speed and simplify the measurement of KN.

This goal is achieved by the fact that the measuring instrument for the nonlinearity coefficient of the sawtooth voltage, which contains a series-connected differentiating capacitance, an amplitude-limiting and a buffer cascade, two identical cascade controllers, each of which is implemented in the form of series-connected adjustable time

S delay connected to the source of clock pulses, the driver of the pulse and the key associated with the output of the buffer stage, two peak detector. Connected respectively to the outputs of the keys, an analog subtraction circuit whose inputs are connected respectively to the outputs of the peak detectors, an integrator, a comparator whose input is connected to the integrator's output indicator, and a serially connected differentiating element.  and a third peak detector, with the differentiating capacitance and the differentiating element connected to the measuring input of the device, two switches, two valves, a clock generator and a pulse frequency generator, a time delay circuit, an analog inverter, a counter, a register, a third driver and a control unit, the second input of the comparator is connected to the common bus of the device, its output is connected to the control circuit and, via the third driver, to the control input of the second switch, the integral input torus connected to the output of the first switch, one of whose inputs is coupled to the output of the analog circuit howling, subtracting, and.  the other with the output of the second switch, one of the inputs of which is connected to the output of the inverter, and the other with its input and the output of the third peak detector, the input of the time delay circuit: and connected to the clock source, and its output and output of the clock generator through the first the gate is connected to the control unit, the pulse generator of the exemplary frequency is connected via a second gate to the counting input of the counter, the discharge bits of which through the register are connected by an indicator, and the high discharge output of the counter is connected It is connected to the control unit, the outputs of which are connected respectively to the control loop of the first switch, the second valve and to the installation inputs of the counter and register. .  FIG.  1 is a functional diagram of the proposed device; FIG. 2 shows temporary diagrams 1 explaining the principle of its operation; in fig.  3 embodiment of peak detectors; in fig.  4 shows the voltage forms at the output of the integrator 14 and the former 31.  The meter KN MON contains a differentiating capacitor 1 connected to an amplifier-limiting device 2 connected to the buffer helmet pu 3, two identical gating cascades, the first of which is implemented in the hanging serial connection of the adjustable time delays 4, the strobe driver 5 and the key 6, the second one in the form of a serial connection of an adjustable time delay 7, a pulse generator 8 and a key 9. The time delay inputs are connected to the clock source U, and the key inputs are connected to the buffer output, cascade a 3.  In addition, the meter contains two peak detectors 10 and 11 connected respectively to the outputs of the keys, analogue subtracting circuit 12, the inputs of the controller are connected respectively to the outputs of the peak detectors 1O and II, and the output through the first switch 13 and the integrator 14 with a charging circuit 15, 16 and amplify / YuM 17 voltage is connected to the input of the comparator 18, differentiating element 19, third peak detector 2O and inverter 21 connected in series, counter 22, register 23 and digital indicator 24 switched on, time delay element 25, generator a clock torus 26, a pulse frequency generator 27, a second switch 28, passing valves 29 and 30, a third driver 31, and a control unit 32.  In the circuit of the embodiment of the peak detectors 10, 11 and 2O (Fig.  3) includes a comparing operational amplifier 33, a charging diode 34, in series with which included a charging transistor 35 and a storage capacitor 36, connected by its first lead to the input of the repeater 37 voltage on the operational amplifier with field-input transistors, resis. the divisive divider 38, 39 ,.  protective zener diode 40, leveling resistor 4 and button 42 discharge.  8 7 "A silicon planar triode of the pn type is used as a charge transistor 35.  The device works as follows.  In the initial state, the device inputs are disconnected from the sources of the sawtooth U, and the synchronizing U.  stress  In this case, the keys 6 and 9 pa-i are closed, the voltages and and Ue, respectively, at the outputs of the analogue subtracting circuit 12 and the differentiating element 19 are zero.  In It bits of counter 22, an additional integer M is written in the additional code, and bits from (ic + l) to the most significant one are oriented at the position of one.  In the peak detectors 10, 11, and 20, the discharge buttons 42 are closed, so the voltages at the outputs of the picoBOGO detector 2O and the analogue inverter 2 I are equal and -80 mlV, respectively (J 80 mlV.  One of these voltages (for example, U {j) through the switches 28 and 13 acts on the input of the integrator 14 and, after integration, is compared with a comparator 18 with zero voltage.  At the time the comparator 18 triggers, a signal is generated that is normalized in amplitude by the driver 31.  Under the action of a voltage pulse (Fig. 4) from the output of the imaging unit 31, the element 28 is triggered, connecting the O-to-Ut voltage to the integrator 14.  In this case, the direction of the voltage id is reversed, which leads to a new operation of the comparator 18 and the switch 28 and so on. d.  Therefore, the integrator 14 is in the mode of relaxation oscillations, and the constant component of its output voltage is zero, and if the current value of the voltage Uxj is removed from the zero level does not exceed the deadband in amplitude (Fig.  4) comparator 18, which is a millivolt unit.  Thus, in the proposed device, the measurement error of the VF caused by the input current and the emf of mixing of the integrator 14 is practically eliminated, and therefore there is no strict requirement for the values of which.  In the working state of the meter, the discharge buttons 42 at the peak detectors 10, 11 and 20 are open and the inputs are.  The devices are connected respectively to the sawtooth Uy sources, and synchronizing DC voltages.  Before the arrival of the signal, and the output voltage Uj.  78 peak of the spectrum 20 remains equal to 8 O mlB and the integrator 14 continues to work in the relaxation mode.  Due to the peculiarities of the peak detector circuit 20 (FIG.  3) this mode can be long enough.  1 The feature of the circuit in FIG. 3 is the implementation of the charging circuit.  In addition to the charge diode 34, it also contains a charge transistor 35, turned on so that the potentials on the base and on the collector of the triode are the same at any time.  If the charge diode 34 is blocked, which is the case for (Jg 0, U -80 Mjfi, then the reverse voltage is released mainly on this diode.  The voltage drop across the equalization resistor 41 is a few millivolts.  Therefore, the entire charge transistor 35 is an equipotential region, thereby eliminating the path of discharge of the storage capacitor 36 through the charge circuit.  Since the input resistance of the repeater 37 voltage with transistors is very high (10 -1OOm), the peak detector circuit 20 provides long-term storage of the voltage level E, eg hundreds of minutes if the capacitor 36 of the type K76-P has a capacity of 0.1 µF .  The meter operation can be explained using mathematical expressions.  Thus, with the advent of the first synchronizing pulse Uc (FIG. 2), a DO DO is formed, which, having passed the differentiating capacitance 1, is brought to the amplification with a shocker 10 in the form of a current pulse with amplitude where SL is the value of the differentiating capacitance 1.  The pulse width, containing information about the change in the derivative of the PN, is determined by limiting the differentiated signal from above and is converted into an impulse of direction C.  The entry of the device, the first clock pulse and actuates the adjustable time delays 4, 7 and the element 25 of the time delay.  The durations t and lg of the adjustable delays 4 and 7 are set smoothly and independently, which makes it possible to determine the CNs in any selected area of the PN.  Duration1 (y, delay 25 is chosen such that by the time of its termination the transition to the 7th process of setting the voltage on the output of the analog circuit 12 is completely completed.  To stability of duration  no hard requirements.  At time t (FIG.  2) sipal from the output of the adjustable time hold 4 starts the driver 5.  The first strobe pulse is generated, and through key 6, the first voltage pulse U, the amplitude of the coordinate Up, passes through the peak detector 1O in the form of a constant voltage.  If we ignore the characteristics of the key 6 and assume that the transmission coefficients of nodes 3 and 0 are equal to unity, then the level of constant voltage at the output of the peak detector 1O is equal to, ta) th - the level of limiting amplifier-limiting 2; A is a constant value for a given amplifier; R.  - transfer resistance.  node 2; d- is a derivative of mon at the moment of time I men t.   At the same time, the output of the analog subtracting circuit 12, having a gain factor of the difference signal K, is set to voltage 0.  equal to K.  U (2.  At time b. A second strobe pulse is formed, and a second voltage pulse cut through the key 9 passes, the amplitude of which is.  remembered by the peak detector 11 as a constant voltage level.  In equation (3), Mu is derivative of PN at time of time Ch.  At the output of the analog subtraction circuit 12, after the completion of the transient process, the voltage VW is set. (-) t) Proportional to the difference of the derivatives of the measured PN at the instants of time t and tQ.  The duration of the transient is determined by the inertia of the node 12.  The K C R value determines the sensitivity of the meter and can be adjusted by changing the transmission coefficient stepwise.  Acting on the differentiating element 19 of the nonlinearity coefficient meter, the sawtooth voltage is transformed by this purpose into a voltage pulse and 5 (Fig.  the maximum value of which is locked and remembered by the third peak detector 20.  The storage of an extrinsic, nonvolatile MF is performed as follows.  With the appearance of a negative voltage drop Uc (4ig.  3) diode 34 is unlocked and capacitor 36 starts charging.  During the charging process, the voltage on the capacitance 36 monitors the signal Uj, since this process is continuously monitored by a comparison amplifier 33, to the inverse input of which a signal is output from the output of the peak detector 20.  At the moment when the negative voltage pulse Uj reaches its maximum value and then begins to decrease, the process of the subarameter of the capacitor 36 stops, as the voltage at the signal input of the comparison amplifier 33 becomes less than the voltage at its inverse input.  As a result, the voltage at the output of the matching amplifier 33 reverses its sign, which leads to the blocking of the diode 34.  Thus, a constant is set at the output of the peak detector 20 (FIG.  2) proportional to the maximum value of the derivative of the controlled MO,. , U, u) - the largest value of the derivative of the MO; CQ is the capacitance of differentiating element 19; fto is the resistance of this element; To, koef4 the voltage transmission element of the element 1 The most important consideration of the operation of the meter will continue from the moment the delay time ends (Fig.  2) -.  By a voltage difference U- from the output of the element 25, the valve 29 is unblocked, and the voltage pulses and the idot of the clock generator 2 arrive at the control unit 32.  On the first clock pulse Ug, control unit 32 generates two pulse signals at its outputs.  One of them U lJ breaks the valve 30, and the pulse T o of the exemplary frequency tg from the generator output, 27 begins to fill the counter 8 710.  2, in which the M & raar ay (k +1) ao senior is oriented to the eoinitsa position.  Another pulse ignal. (control of the switch in switch 13 (FIG.  1), as a result of which the last posi- tion of its ingressor 14 to the output of the analogue reading circuit 12.  Since the transition process for voltage Ux has already been completed, the voltage of the integrator 14 does not change linearly (Fig.  4) ill) where t is the resistance of the resistor 15; C - capacitor capacitance 16.  Comparator 18 compares the signal and (i) with a zero level.  At the moment of the comparator 18 srabatan, the voltage drop across its output through the shaper 31 acts on the control input of the switch 28, and a voltage is connected to the output of the latter, the polarity of which is opposite to the polarity of the voltage id.  As can be seen from FIG. 2, the negative polarity has a constant voltage} formed at the output of the peak detector 20.  After the counter is filled with 22 M pulses of an exemplary frequency, all its bits turn out to be in a single position.  With the arrival (M-b) of the signal, separated from the clock pulse u9 (Fig.  2) with the time interval T, i, all the bits of the counter 22 are zeroed out and the negative voltage drop of the output of its most significant bit through the block 32 y.  This function returns the switch 13 to the initial position.  At the same time, the voltage U is disconnected to the input of the integrator 14 for the compensation of the action of the voltage Od.  The output voltage of the integrator 14 at time T; equals fT).  V i -c-ip Further, the voltage () is changed according to the law V. TTRCf and counter 22 continues to fill with pulses.  exemplary frequency about coming from the output of the generator 27.  After a time interval (FIG.  2) the voltage at the output of the integrator 14 reaches zero, which is detected by the operation of the comparator 18.  On the positive overload of its output voltage, control unit 32 forms two pulse signals.  Otsin of them is the negative voltage drop U Q -coding of the 30, and on the counter 22 appears the fixed binary code of the number N I determined from the condition RC-b.  Another signal — the impulse Hanpsprai — unlocks the register 23 for the time tj, which is necessary to confidently write a binary code into it from the output of counter 2. 2  At the end of the pulse, the control unit 32 generates a reset pulse and (5 (2) which, arriving at the installation input of the counter 22, restores its initial state, preparing the device to the next one of. measuring cycle / y.  The contents of register 23 are memorized and displayed in decimal code-specific indicator 24.  Substituting in (9) the controls (4) and (5) gives the following expression for the measurement result represented by the value of the number (du du I Ж d d. -fci (dUn Vdi BOY. -with.  where r - - / - scale factor,: defined by the parameters of the scheme.  From (10) it follows that the readings of the digital indicator 24 with an accuracy up to a scale factor correspond to the measured CN, and when choosing the coefficient COO 1OO, indicator 24 directly highlights the value of the nonlinearity coefficient of the studied part of the saw voltage On.  The value 100 can be set by selecting the value of the number M, which is entered in the additional code in the counter 22 when it is preset.  Upon completion of the time interval Tt, the integrator 14 is again in the mode of relaxation oscillations and its output voltage is maintained at the zero level.  When the second so-called pulse Ug appears (FIG.  2) the next measurement cycle begins and the operation of the proposed device is repeated.  The update rate of indications on 8,712 scoreboard indicator 24 is set by the onierator using control unit 32.  The result of the measurement does not depend on changes in the repetition period T of clock pulses Ug, the reference frequency (j, the voltage of the reference source, and on the parameters of the auxiliary PN produced by the integrator 14.  Due to the use of the two-stroke integration mode, the measurement error due to the absorption and characteristics and leakage points of the storage tank 15 is eliminated and the noise immunity of the circuit is improved.  All this makes it possible to obtain in the proposed device a higher accuracy of measurement, a higher accuracy of determining KN and greater sensitivity (resolution).  The device has a higher speed.  As viino from the time diagrams (FIG.  2), the time taken to establish an instrument reading does not exceed T + t3aA. The device provides the ability to memorize and the length of the south storage of the result of the measurement in digital form, which is important for automating the control of the VF and for interfacing the meter with the computer.  Ф О р.  The invention measures a sawtooth voltage nonlinearity coefficient meter containing a series-connected differentiating capacitance, an amplifier-limiter and a buffer cascade, two gates, made in the form of serially connected adjustable time delays connected to a source of clock pulses, gate formers of strobe pulses and keys.  connected to the output of the buffer stage, two peak detectors connected respectively to the outputs of the keys, an analog subtraction circuit whose inputs are connected respectively to the outputs of the peak detectors, an integrator, a comparator whose input is connected to the output of the integrator, an indicator, and a series-connected differential element and the third peak detector, the differentiating capacitance and the differentiating element being connected to the measuring input of the device, which is, in order to increase accuracy, faster Corollary and simplification.  Neither the measurement process, 13 pv switches, ova valve, clock pulse generator and pulse generator of exemplary frequency, temporary looping circuit, analog inverter, counter, register, third driver and corrugator, are entered into it, while the second input of the comparator is associated with a common one. By the bus of the device, its input is connected to the control circuit and through the third driver with the control input of the second switch, the integrator input is connected to the output of the first switch, one of whose inputs is connected to the output. analog circuit, and the other with the output of the second switch, one of the inputs of which is connected to the output of the analog inverter, and the other with its input and the output of the third peak detector, the input of the time delay circuit is connected to the sync pulse 07, and its output and the output of the clock generator through the first valve is connected. to the control unit, a pulse generator of exemplary frequency through the second valve is connected to the counter input of the counter, the outputs of the latter through a register are connected to the indicator, and the high end of the counter is connected to the control unit, the outputs of which are connected respectively to the control input of the first switch, second valve and to the installation inputs of the counter and register6.  Sources of information taken into account during the examination 1. USSR Author's Certificate No. 169678, cl.  5 01R 29/04.  2 USSR Author's Certificate No. 742830, cl.   29/02 (prototype).

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Claims (1)

Claim The sawtooth non-linearity coefficient meter, which contains a differentiating capacitance in series, has a limiter and a buffer cascade, two gating cascades made in the form of adjustable time delays connected in series, connected to a clock source, a strobe driver and a key connected. connected to the output of the buffer cascade, two peak detectors connected respectively to the outputs of the keys, an analog subtraction circuit, the inputs of which are connected respectively to the outputs of the peak detectors, an integrator, a comparator, the input of which is connected to the output of the integrator, an indicator, and a differentiating element and a third connected in series peak detector, wherein the differentiating capacitance and the differentiating element are connected to the measuring input of the device, characterized in that, in order to increase accuracy, speed and simplification of the measurement process, two switches, two valves, a clock generator and a pulse generator of a reference frequency, a time delay circuit, an analog inverter, a counter, a register, a third driver and a control unit are introduced into it, while the second input of the comparator is connected to the device common bus , its output is connected to the control circuit and, through the third driver, to the control input of the second switch, the integrator input is connected to the output of the first switch, one of the inputs of which is connected to the analog output of the subtraction circuit, and the other with the output of the second switch, one of the inputs of which is connected to the output of the analog inverter, and the other with its input and the output of the third peak detector, the input of the time delay circuit is connected to the clock source14, and its output and output the clock generator through the first valve is connected to the control unit, the pulse generator of the model frequency through 5 the second valve is connected to the counter input of the counter, the outputs of the latter through the register are connected to the indicator, and the output of the senior zryada counter is connected to a control unit which outputs are connected respectively to U control input of the first switch, the second valve and the inputs to the installation counter and register.