SU1478130A1 - Device for suppressing non-stabilities of stroboscopic recorder - Google Patents

Abstract

This invention relates to electrical measuring technology and can be used in stroboscopic installations when observing periodic signals. The purpose of the invention is to enhance the functionality while improving accuracy. Through the voltage switching unit 22, a sequence of two reference voltages is fed to the input of the external sweep of the stroboscopic oscilloscope 6 via buses 30, 31 and the output signal from the sawtooth generator 8, which allows the three periodic blocks 9, 10 and 11 to be memorized sequentially signal at three points, using subtraction blocks 15, 16 and division block 17, to carry out not only the correction of additive, but also multiplicative measurement errors. Moreover, the correction is performed for a periodic signal of an arbitrary shape every moment of time for the conversion period. In addition, the drawing shows a signal generator 1, a probing signal source 2, a system 3, a probing signal receiver 4, a synchronization unit 5, a cathode ray tube 7, low-pass filters 12, 13 and 14, a ring register 18, drivers 19, 20 and 21 pulses, adder 23, keys 24, 25 and 26, terminals 27, 28 and 29. 1 dw., 1 hp f-ly.

Description

This invention relates to electrical measuring technology and can be used in stroboscopic installations when observing periodic signals.

The purpose of the invention is to expand the functionality with a one-time increase in accuracy.

The drawing shows a block diagram of a device for the instability of a stroboscopic recorder.

The diagram shows a signal generator 1, a probing signal source 2, a system 3, a probing signal receiver 4, a synchronization unit 5, a stroboscopic oscilloscope 6, a two-coordinate recorder 7, a sawtooth voltage generator 8 with an adjustable slew rate, the first 9, the second 10 and the third 11 blocks of sampling and storage, first 12, second 13 and third 14 low-pass filters, first 15 and second 16 subtractors, dividing unit 17, ring register 18, first 19, second 20 and third 21 pulse shapers, switching unit 22 a sweep array consisting of an adder 23 and keys 24-26. In addition, the diagram shows terminals 27-29 and tires 30 and 31 of the normalized and reference potentiometers, respectively.

The input of the synchronization unit 5 is connected to the output of the signal generator 1 and to terminal 28, and its output is connected to the synchronization input of the stroboscopic oscilloscope 6, the signal input of which is connected to the output of the probe 4 of the probing signal, the horizontal deflection input

the two-coordinate recorder 7 is connected to the output of the sawtooth generator 8, the inputs of the sampling and storage units 9-11 are connected to the output of the vertical deflection amplifier of the stroboscopic oscilloscope 6, and their outputs respectively through the low-pass filters 12-14 are connected to the inputs of the subtraction blocks 15 and 16, with the output

the lowpass filter 13 is connected to the inputs of subtracting units 15 and 16, and the outputs of lowpass filters 12 and 14 are respectively connected to the first and second inputs of subtractive blocks 15 and 16, the outputs of which are connected to the inputs of dividing unit 17, and its output is connected to the vertical input deviations of the two-coordinate recorder 7. The input of the ring register 18 is connected to the output of the synchronization unit 5 and to the synchronization input of the stroboscopic oscilloscope 6, and its three outputs, respectively, through shapers 19, 20 and 21 pulses - with control inputs locks 11, 10 and 9, the sample and hold. The voltage sweep switching unit 22 is connected to the output, which is the output of the adder 23, with the external sweep input of the stroboscopic oscilloscope 6, the controlled keys 24-26 are connected by the outputs to the inputs of the adder 23, and their inputs are 0

0

These are the third, second and first inputs of the voltage switching unit 22. The terminal 27 is connected to the source output of the 2 probing signal, terminal 29 is connected to the receiver 4 of the probing signal, the first input of the voltage switching unit 22 is connected to the output of the sawtooth generator 8 with an adjustable slew rate and to the input of the horizontal deflection amplifier of the X-ray recorder 7 , the third input is with bus 30, to which an auxiliary normalized potential U is fed, the second input is with bus 31, to which an auxiliary reference potential LJ yun is supplied. The control inputs of the keys 26, 25 and 24 are the fourth, fifth and sixth inputs of the voltage switching unit 22 of the sweep voltage and are respectively connected to the first output of the ring register 18 and to the input of the third pulse generator 21, to the second output of the ring register 18 and to the input the second shaper 20 pulses, with the third output of the ring register 18 and with the input of the first

shaper 19 pulses. i

The device works as follows.

The excitation voltage Ur (t) from the signal generator 1 with a period t, is supplied to the synchronization unit 5 and the system under study 3, which is simultaneously affected by the source 2 of the probing signal. As a result, the signal appearing at terminal 29 is registered by the receiver 4 of the probing signal and from its output goes to the signal input of the stroboscopic oscilloscope 6. The synchronization input of the oscilloscope 6 and the input of the ring register 18 receive pulses from the synchronization unit 5, the amplitude and duration of which does not depend on the shape and amplitude of the output voltage of the signal generator 1. Each sync pulse from the output of synchronization unit 5 starts a stroboscopic oscilloscope 6 and a ring register 18 with the frequency of the excitation signal f 1 / t | -. In this case, when the first synchronization pulse arrives, the level 1 appears at the first output of the ring register 18, while

the second and third outputs present level O. When the second and third clock pulses of Gn arrive, the three outputs of the ring register

there is respectively a combination of 10

15

20

25

thirty

five

0

five

0

qi levels o

 R

 ABOUT

and

Oh oh

five

1. Next, when the fourth pulse arrives, the cycle repeats. The formers 19–21 pulses start — from a slice of the output pulses of the ring register 18. The amplitude and duration of the pulses at the outputs of the formers 19–21 pulses does not depend on the shape of the input signals. The occurrence of level 1 at the first output of the ring register 18 and its disappearance leads to the sequential opening of the key 26 in the block 22 of the switching voltage switch, the screwdriver and the block 9 of sampling and storage in the first channel consisting of blocks 9 and 12. The keys 24 and 25 in the sweep voltage switching unit 22 and the sampling and storage units 10 and 11 remain closed. Upon receipt of the second and third synchronization pulses, the key 25 and the sampling and storage unit 10, the key 24 and the sampling and storage unit 11 are opened respectively. The alternate operation of the keys 26, 25 and 24 as the sync pulses arrive leads to the fact that after equal intervals the input of the external sweep of the stroboscopic oscilloscope 6 from the output of the adder 23 one after another receives three voltages - slowly changing voltage U p (T) sweep from a sawtooth voltage generator 8 with an adjustable slew rate, constant voltage Uon from bus 31 and constant voltage U bur from bus 30. Thus, at the input of the external sweep of the stroboscopic oscilloscope 6 alternately exist three source voltages. One of them (from the generator output 8 Up (T)) is current and determines the time of the complete recording cycle T c of the measured U (t) signal with period tr. The cycle time T c depends on the rate of increase of the sawtooth voltage, and its beginning is determined by the moment the generator 8 is started. The other two voltages are auxiliary and are determined by the point on the tc signal (for Uen) and t "(for U nor) selected as a reference

14

and normalization. Their values are fixed, but different and do not fall outside the voltage range of the external sweep of a stroboscopic oscilloscope 6,

When the stroboscopic oscilloscope is operating in the recording mode, its external sweep input is usually supplied with the voltage U0 (T) varying during the TC time from the generator 8, and the cycle time TC exceeds the excitation voltage tj by several orders of magnitude. from the signal generator 1. In this case, a temporal transformation (stretching) of a fast measuring signal supplied to the signal input of a stroboscopic oscilloscope 6 to a slow analog voltage at the output of the oscilloscope vertical deflection amplifier 6 occurs. The shape of the analog voltage is identical to that studied, but recorded on a different scale during the TC. Delivering an external sweep of the stroboscopic oscilloscope 6 through the voltage switching unit 22 of the sweep of three successively switched voltage levels, one of which changes during the recording time Tc, and the other two are fixed, causes the probe signal 4 to come from To the signal input, a fast measured signal with a period of th is converted at the output of the oscilloscope 6 into an analog voltage consisting of three successively alternating voltage samples. The separation of samples into three channels occurs by alternately opening these channels when blocks 9–11 of sampling and storage are triggered synchronously with pulses at the output of the ring register 18. The duration of open and open blocks of blocks 9–11 corresponds to the pulses of the formers 19- 21 and is determined by the time of memorization of the amplitude of the samples, which is established by a much shorter period of the excitation signal t). This avoids the influence of adjacent time samples on the results of their subsequent average nothing in every channel. Filters 12-14 of the lower frequencies eliminate the high frequency noise present in the extended analog output signal and drive (for

-

306

averaging account) to an increase in the signal-to-noise ratio, if constant n. Obtained after temporal transformation and averaging of the voltage U5 (T) at the output of low-pass filters 12-14, respectively, of the first, second and third channels are generally recorded as

five

0

five

0

five

0

five

0

five

U, (T) K (T) -Uc (t. () + U (T), where K (T) is the averaged conversion (gain) coefficient of the measuring path of the device, which includes the sounding source 2, the sounding receiver 4 -, la, stroboscopic oscilloscope 6.

U6 (t;) is the instantaneous value of the voltage coming from the output of the receiver 4 of the probing signal at time t; to the input of the stroboscopic oscilloscope 6, which is obtained under the influence of the instantaneous voltage U (t.) from the signal generator 1 with a period t ,.

Ucj (T) is the averaged drift voltage of the measuring path.

The voltage Uc (t) is not randomly dependent on T, being a periodic function of the voltage of the signal generator 1, and time t. runs through all the values of its period (from 0 to th), while K (T) and (T) depend on T randomly and are the source of slowly changing, respectively, multiplicative instabilities of the signal under study. Dividing the sequences of samples into channels leads to the fact that the first channel (blocks 9 and 12 of the sample and storage) receive samples of voltages U. (T) obtained at the moments of connection to the input of the external sweep of the stroboscopic oscillograph sweep Up (T) from generator 8. This allows you to record all the instantaneous values of the repetitive signal under study, since for a full cycle U p (T) time t; runs through all values of the period of the signal under study t ,,. When a direct voltage U of the sampling voltage U0 (T) of the investigated Signal U4 (te) is applied to the external sweep input, the corresponding time points fall into the second channel, and when voltage U Up is sampled

voltage UH (T) correspond to the signal U. (tw) under study at time t, t and fall into the third channel. Thus, it can be seen that the voltages at the output of the first U- (T), second U0 (T) and third UH (T) channels are measured at different points in the input signal period t ;, tc, tH, respectively. Voltage UT) is the main detected voltage carrying information about the input signal, and U0 (T) and UH (T) are auxiliary and serve to suppress the zero-level drift of the output voltage of the measuring path U- (T) and fluctuations of its conversion coefficient K (T), determined by possible instabilities of the source 2 of the probe signal, the receiver 4 of the probe signal and the stroboscopic oscilloscope 6. Fixed with respect to the sync pulses the time points te and tH at which the samples of the reference Ue (T) are taken and the normalization voltage UH (T) is set by the potentials U on and U H0f at the inputs of the external sweep switching unit 22, while the current time t is shifted relative to the start of the sync pulse in each subsequent period of the signal under study synchronously with the change in the output potential of the generator 8 sawtooth voltage with adjustable rate of rise.

Eliminating the effect of the drift U (T) on the signals in the first and third channels is obtained by subtracting from the output

the voltage of the first channel U. (T) on the voltage of the second reference channel

U0 (T) in block 15 of subtraction and, accordingly, subtraction from the output voltage of the third channel U (T) voltage of the second reference channel U0 (T) in block 16 of subtraction. The correct setting of the subtracted sequence of samples of the second reference channel is obtained when switching the outputs of the channels at the inputs of blocks 15 and 16 of the subtraction. The obtained two differences in voltage at the outputs of blocks 15 and 16 of the subtraction are fed to the inputs of block 17, at the output of which, the ratio A does not depend on the influence of the instability K (T)

A Ui (T) -U, (T) 1 „

. and „(t) -i. (t) ue (tH) -uc (te)

- with Q 5 Q

one

five

0

u (t) -uc (t ..) -uc (to) and

and proportional to only Uc (t;). Thus, the magnitude A at the output of the device is independent of the drift and instability of the conversion coefficient. The relation Uc (t ,,) Uc (t0) is achieved by setting fixed voltages U vof and Ueo at the input of the voltage sweep switching unit 22. The preliminary calibration of the device determines the correspondence between the magnitude A and the specific physical parameter measured in the experiment.

In devices in which the conversion factor K is sufficiently stable and only high-frequency noise and drift are to be suppressed, the third channel and one auxiliary voltage U norm can be eliminated. When building a device according to a two-channel scheme, its output will be the subtraction unit 15, the ring register 18 may be replaced by a trigger, and the auxiliary source voltage Uop, in a particular case, may be zero. Such a scheme can be used, in particular, to eliminate the zero drift of the stroboscopic oscilloscope itself.

To eliminate n types of instabilities, a circuit with a n + 1 channel and the corresponding ring register, a sweep voltage switching unit and computational blocks (subtraction, division, etc.) can be applied. If necessary, in the proposed device, a sawtooth voltage generator with an adjustable slew rate, a ring register, subtraction and division units can be made in the form of a computer.

Claims (2)

1. A device for suppressing instabilities of a stroboscopic recorder, containing a terminal signal generator for connecting the system under study, a stroboscopic oscilloscope, a first low-pass filter connected by an output to the first input of a subtraction unit, a second low-pass filter connected by an output to a second input of a subtrac Nor, a two-coordinate recorder, a horizontal deflection input connected to the output of a saw-tooth generator, characterized in that, in order to expand its functionality while improving accuracy, it contains a source of a sounding signal, a sounding receiver, a synchronization unit, three blocks sampling and storage, the third low-pass filter, the second subtraction unit, the division unit, a ring register, three pulse shapers, and a sweep voltage switching unit, the first input of which the second input is with the reference potential bus, the third input is with the normalization potential bus, and the output is with the external sweep input of the stroboscopic oscilloscope, the signal input of which is connected to the output of the receiver of the probing signal, whose input connected to one terminal for connecting the system under study, the other terminal is connected to the output of the signal generator and the input of the synchronization unit, and a third terminal is connected to the source of the probing signal, the synchronization input is st of the oscilloscope is connected to the output of the synchronization unit and the input of the ring register, the first output of which is connected to the fourth input of the voltage sweep switching unit and the input of the third pulse generator, the output of which is connected to the control input of the first sampling and storage unit, the second output with the fifth input of the voltage switching unit of the sweep and the input of the second pulse driver, the output of which is connected to the control input 0 five 0 5 0 five 0 the second sampling and storage unit, the third output — with the sixth input of the sweep voltage switching unit and the input of the first pulse shaper, the output of which is connected to the control input of the third sampling and storage unit, the input of which is connected to the output of the vertical deflection amplifier of the stroboscopic oscilloscope and inputs the first and second blocks of sampling and storage, and the output is connected to the input of the third low-pass filter; the second block of sampling and storage is connected to the input of the second low-pass filter; and the storage is connected to the output of the first lowpass filter, the first input of the second subtraction unit is connected to the output of the second lowpass filter, the output of the third lowpass filter is connected to the second input of the second subtraction unit, the output of which is connected to the second input of the dividing unit, the first input of which is connected with the output of the first subtraction unit, and the output with the input of the vertical deflection of the two-coordinate recorder. 2. The device according to claim 1, characterized in that the sweep voltage switching unit contains three keys, an adder, the output of which is connected to the output of the voltage sweep switching unit, and its inputs are connected to the outputs of the first, second and third keys, whose inputs connected to the first, second, and third inputs of the voltage sweep switching unit, and their control inputs, respectively, with the fourth, fifth, and sixth inputs of the sweep voltage switching unit.