SU1372234A1 - Oscillographic method of measuring time parameters of signals - Google Patents

Abstract

The invention relates to a radio measuring technique. The oscillographic method of measuring the time parameters of signals is implemented in a device containing a strobe converter 1, a comparator 2, an amplifier (V) 3 vertical deflection, a cathode ray tube 4, a U 5 light, a counting trigger 14, a generator (d) 9 fast ramp voltage, synchronizer Yu, horizontal deflection amplifier 11, multiplexers 12, 17, digital-to-analog converter 13, counters 7, 8, 14, and 22 auto-shift, labels, mode and accumulations, respectively, potentiometers 15 and 16 Start and Stop, respectively, element And 18, G 19 reference frequency, reversible counter 20, register 21 and digital indicator 23. The essence of the method lies in the fact that the determination of the specified levels of the signal under investigation, between which the time interval of interest is concluded, is carried out in a transformed time scale by gating, and the measurement the time interval selected by these levels is carried out in real time. The accuracy of short time intervals is improved. 3 il. (L NSchn 3

Description

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The invention of radio communication is to measure. it can be used as a time zone for measuring the time AND) 1X parameters of a pulse signal, time-iep pulse duration, rise time.

The purpose of the invention is to improve the accuracy of measurement of short time intervals.

The essence of the method lies in the fact that the determination of the specified levels of the signal under study, between which the time interval is interesting, is carried out in a transformed time scale by the gating method, and the time interval selected using these ypoBHefi is carried out in real time.

In this case, the error component due to the finite rise time of the input circuit of the meter is reduced using the gating method, which allows the minimum rise time value to be realized. On the other hand, the error component inherent in the known stroboscopic methods for measuring time intervals and associated with the imperfection of the time scale generated in a transformed time scale is reduced by forming a time scale in real time, for example, using a precision quartz oscillator.

Known stroboscopic methods do not allow the measurement of short time intervals on a real time scale, with high accuracy. This is explained by the general principle that underlies the construction of all wide, off-line strobe transducers. Only the strobe-converter input circuits have a high speed and a short rise time (: 30 ps), and amplification, conversion, and measurement of instantaneous samples of the signal under investigation is carried out after they are stored in the storage capacitor, in a relatively narrow band and low frequency circuit. on the order of microseconds. The error with which the instant of the measurement result at the output of the strobe-converter in real time can be recorded

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(the instant of coincidence of the instantaneous value of the signal with the preset Start or Stop level) cannot be less than the rise time of the stroboscopic converter in real time. This time is determined by the output circuit of the strobe converter and is 1 µs.

Thus, stroboscopic methods are not used for real-time measurements because of the contradiction between the short rise time of the input circuit of the strobe converter and the long rise time of its output circuit.

The proposed method eliminates this contradiction due to the fact that the coincidence of the instantaneous samples of the signal under investigation with the specified Start and Stop levels is not used to fix the corresponding points in time, as in all known methods, but to fix the corresponding values of the second sweep signal, in which a coincidence has occurred. The time instants corresponding to the coincidence of the instantaneous values of the signal under investigation with the specified Start and Stop levels are recorded in real time by comparing the first sweep signal with the previously recorded values of the second sweep signal, without waiting for this step of the result of comparing the output strobe signal converter with given levels. The procedure of allocating initial and final times, limiting the desired interval, in two stages (first fixes the first and second values of the second sweep signal, and then the time points corresponding to them) is new. And it allows for the measurement of time intervals with previously unattainable accuracy, which is limited by the rise time of the strobe pulse of the stroboscopic converter (ps).

Figure 1 shows a block diagram of a device for carrying out the proposed method; Fig. 2 shows voltage diagrams at characteristic points of the circuit (the diagrams correspond to the symbols on the block diagram); in Fig. 3 - the oscillogram of the signal under study. when measuring the pulse duration t at a level of 0.5.

The device contains a strobe converter 1, a comparator 2, a vertical deflection amplifier 3, an electron yo-ray tube 4, amplify 5 illumination, a counting trigger 6, an auto-shift counter 7, a counter 8 marks, a fast sawtooth generator 9, a synchronizer Yu, horizontal deflection amplifier 11, first multiplexer 12, digital-to-analog converter (DAC) 13, mode counter 14, potentiometer 15 Start, potentiometer 16 Stop, second multiplexer 17, element 18, reference frequency generator 19, reversible counter 20, register 21, sche Accumulator 22, digital indicator 23.

The input of the gate converter 1 is connected to the bus of the signal under study, the input of the gate is connected to the input of comparator 2, and the output is through the vertical deflection amplifier 3 with the vertical deflection plates of the cathode ray tube 4. The modulator (not shown) of the cathode ray tube 4 is connected through the amplifier 5 illumination to the output of the comparator 2, the installation input of the counting trigger 6, the counting inputs of the auto-shift counter 7 and the counter 8 tags. The first input of the comparator 2 is connected via the generator 9 of a fast sawtooth voltage to the counting input of the counting trigger 6 and the output of the synchronizer 10, whose input is connected to the synchronization clock. The second input of the comparator 2 is connected via a horizontal deflection amplifier 11 to the horizontal deflection plates of the cathode ray tube 4 and to the output of the first multiplexer 12. The code output of the auto-shift counter 7 is connected via a digital-to-analog converter 13 to the inputs of the first multiplexer 12, and the overflow output to the inputs of the first multiplexer 12. The overflow output of the counter 8 is connected to the inputs of the first multiplexer 12, the output of which is connected to the counting input of the mode counter 14 and to the installation inputs of the counter 7 A. osdviga counter 8 and tags. The input of the first multiplexer 12 is connected to the average output of the potentiometer 15

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The start and the input are with the middle gate of the 16 Stop potentiometer, the extreme terminals of which are connected to the power sources of opposite polarity. The high-order output of the mode counter 14 is connected to the control inputs of the first multiplexer 12 and the second multiplexer 17, and the low-end output is connected to the control inputs of the same multiplexers, whose blocking outputs are connected to the zero-potential bus (housing). The inputs of the second multiplexer are also connected to the zero potential bus. The output of the counting trigger 6 is connected to the first input element And 18, the second input of which is connected to the output of the reference frequency generator 19, and the output - to the inputs of the second multiplexer 17, whose outputs are connected to the Loan and Transfer inputs of the reversible counter 20. The code output of the reversible counter 20 is connected to the information input of the register 21, and the installation input of the reversible counter 20 and the synchronizing input of the register 21 are connected to the overflow output of the accumulation counter 22, the counting input of which is connected to the overflow output of the counter ka 14 modes. The output of the register 21 is connected to the input of the digital indicator 23. At the same time, the connection between the auto-shift counter 7 and the digital-to-analogue converter 13, the reversible counter 20 and the register 21, the register 21 and the digital indicator 23 is made by multi-bit buses ( figure 1 arrows).

The strobe converter 1 contains a bridge-type diode mixer, an amplifier, and a strobe generator.

The vertical deflection amplifier 3 and the horizontal deflection amplifier 11 are made according to a differential circuit based on amplifying Cc Scales of the O-OB type.

Illumination amplifier 5 is assembled on common base type cascades, common emitter and common collector. A differentiating chain is used in the circuit to form the duration of the backlight pulse.

The synchronizer 10 contains an input amplifier, a high-speed bistable trigger, a switch

polarities, output driver and delay circuit.

The first multiplexer 12 and the second multiplexer 17 contain a decoder and the core of a four-channel switch.

The proposed method using this device is carried out as follows.

The signal under study is fed to the input of the strobe converter 1, which samples the instantaneous values of this signal at times t,

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gates determined by the signal from the output of comparator 2 (Fig. 2d). The sampling of the signal under study, obtained by gating, comes from the output of the strobe converter 1 through the amplifier 3 of vertical deflection onto the vertical deflection plates of the cathode ray tube 4.

Comparator 2 compares the first sweep signal (Fig. 26) produced by the fast sawtooth generator 9 from the synchronization signals (Fig. 2a) from the output of the synchronizer 10 with the second sweep signal (Fig. 2b) coming from the output of the first multiplexer 12 (signals coming from the output of the first multiplexer are indicated by a dotted line).

One cycle of operation of this device is divided into four clock cycles (Fig. 2). In the first clock cycle, the output of multiplexer 12 receives the voltage from the output of a digital-to-analog converter 13 (fig. 2b), controlled by an automatic shift counter 7, which counts the number of gates performed. As a result, a stepwise increasing sawtooth voltage is formed at the output of the converter 13, which automatically shifts the gating moment by one step after the next gating. The same voltage is supplied through the horizontal deflection amplifier 11 to the horizontal deflection plates of the tube 4, and the point image is scanned. The illumination of the image points is carried out by a strobe signal coming through

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amplifier 5 light on the modulator tube 4.

The auto-shift of the gating moment continues until an overflow signal appears at the output of the auto-shift counter 7, which is fed from the output of the multiplexer 12 to the counting input of the mode counter 14. The mode counter 14 changes its state by one (in the counter 14 is recorded 2) and thereby connects the input of the multiplexer 12 to its output.

At the same time, the signal from the output of the multiplexer 12 is fed to the installation inputs of the auto-shift counter 7 and the counter 8 marks, setting them to the initial state. From this moment (Fig. 2), the second cycle of operation of the device begins.

During the second cycle, the comparator 2 compares the fast sawtooth voltage from the output of the generator 5 to the constant voltage received through the multiplexer 12 from the 15 Start potentiometer. At the same time, the input signal is gated at one point at the moment of time (Figure 2d). The gating signal, coming from the output of the comparator 2 through the illumination amplifier 5 to the modulator tube 4, illuminates the point on the signal at which gating is performed. Due to the additional light pulses during the second cycle, the point on the signal image corresponding to the point in time is highlighted by the others and can be used as a rhythm Start (Fig. 3). The position of this mark on the signal image is adjusted by a 15-start potentiometer by changing the DC voltage applied to comparator 2.

The gating of the signal under investigation at the Start point continues until an overflow signal appears at the output of the counter 8 marks. The overflow signal comes from the output of counter 8 through the multiplexer 12 channel open in the second one to its output and then to the counting input of mode counter 14 and the installation inputs of counters 7 and 8. The mode counter 14 increases its state by one (3 is recorded in the counter) and connects the multiplexer input 12

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to the exit. Counters 7 and 8 are set to the initial state. The third cycle of operation of the device begins (Fig. 2).

In the third cycle, the dotted image of the signal under investigation is reconstructed on the tube screen in the same way as in the first cycle. The duration of the first and third cycles is determined by the capacity N of the automatic shift counter 7 (in this case N 256) and the repetition period of the clock pulses (Fig. 2a). The cycle number and mode of operation of the entire device are determined by the mode counter 14, which contains two counting triggers and has a capacity equal to four, in accordance with the number of device operation cycles. After an overflow in the third cycle of the auto shift offset counter 7, the overflow signal is output from the multiplexer 12 to the counter 14 and the fourth cycle of operation of the device begins.

In the fourth cycle, the comparator, 2, compares a fast sawtooth voltage with a constant voltage coming from a 16 Stop potentiometer. At the same time, the input signal is sampled at one point at the instant of time.

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(figg). In the image of the signal, the luminous stop label is highlighted, corresponding to the time of gating. The position of this mark is adjusted by a 16 Stop potentiometer. The duration of the second and fourth cycles is determined by the capacity ha of the counter of the 8 mark (in this case, m 10) and the repetition period of the clock pulses (Fig. 2a). Thus, the brightness of the Start and Stop marks in relation to the brightness of the remaining points on the signal image is determined by the ratio of the capacitances of the counters 7 and B. Each of the N points on the signal image is highlighted twice in one cycle of operation, in the first and third cycles, and each of the marks are held m times in the second and fourth cycles, respectively.

During the operation of this device, the sequence of its operation cycles is continuously repeated 1, 2, 3, 4, 1, 2, 3, 4, 1, etc. At the same time, on the screen of the tube 4, a dotted image of the signal under investigation in a transformed time scale, formed during the first and third cycles, is observed with two brightness marks, which are illuminated during the second and fourth cycles (Fig. 3).

Measurements start from

determine the amplitude of the investigated

signal on a scale applied

on the screen of the tube 4 (fig.Z). Then, based on the obtained value of Ua; y ,,

Constant start and stop levels are calculated, between which the time interval of interest is enclosed. For example, when measuring the rise time of the front of the pulse under investigation, the Start and Stop levels are 0.1 and 0.9 and, respectively (Fig. 3). Mark the levels of start and stop on the scale of the tube. For example, in FIG. 3, these levels are marked by their alignment with dotted lines printed on the screen of the tube 4.

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Comparison of the instantaneous values of the investigated signal with the marked

The 30 Start and Stop levels are scaled visually around the tube screen. Moreover, to record (memorize) the first and second values of the second sweep signal, in which the instantaneous values of the signal under investigation are equal to the marked Start and Stop levels, set the Start and Stop labels at the intersection points of the section of interest for the signal under investigation using potentiometers 15 and 16 for example, the pulse front (Fig. 3), with marked Start and Stop levels, respectively. Memorization (fixation)

5, the first and second values of the second sweep signal are set by fixing the axis of the corresponding potentiometer (Start or Stop, FIG. 1) to the corresponding position.

The luminance marks are necessary in this device to indicate those points in the signal image, the temporal position of which relative to the synchronization signal corresponds to the values of the second sweep signal fixed on the 15 Start and 16 Stop potentiometers, and are used to combine the specified points with the exact point

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we intersect the signal with the start and stop levels. If the instantaneous values of the signal under study are compared with the Start and Stop levels not on the tube screen, but automatically, for example, in analog form using a separate comparator or digitally programmatically using a microprocessor, then the need for velocity labels disappears.

Simultaneously with the strobe of the input signal into the device, auxiliary pulses are formed (fig. 2d), the front of which coincides with the moment of the appearance of the clock pulses (fig. 2a), and the cut is with the strobing moment (fig. 2d). These pulses are generated at the output of the counting trigger 6 and are fed to the input of an AND 18 element, to another input of which a pulse signal of the reference frequency is fed from the generator 19 (Fig. 1). At the output of the And 18 element, bursts of pulses of the reference frequency are formed (Fig. 2e), and the number of pulses in the pack (at the output of the element 18) corresponds to the pulse duration that entered the input of the And 18 element from the output of trigger 6 (Fig. 2e).

The pulse bursts of the reference frequency are fed to the inputs of the second multiplexer 17, which is connected via control inputs in parallel with the first multiplexer 12 and switches simultaneously with it. The multiplexer 17 is also controlled by a mode counter 14.

Since the inputs of the second multiplexer 17 are connected to the common bus (Fig. 1), the signal (bursts of reference frequency pulses) appears at its output only in the second cycle of operation (Fig. 2g), and at the output - only in the fourth tact work (Fig, 2h). Moreover, since in the second cycle of operation, the signal is gated at the point marked with the Start mark, only the bursts of the reference frequency corresponding to the duration of the auxiliary pulse Start signal pass to the output of the multiplexer 17 (Fig. 2g). Similarly, only bursts of the reference frequency, corresponding to the duration of the auxiliary pulse, are passed to the output of the multiplexer 17

about

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signal. Stop (Fig. 2). The rest of the time the outputs of the multiplexer 17 receives the level of logical zero from the common bus (fig.2h, h).

The signals from the outputs of multiplexer 17 are alternately received at the inputs of the Loan and. Transfer of the reversible binary-decimal counter 20, respectively (Fig. 1, 2, h). As a result, after the end of the operation cycle of the device (Fig. 2k), the number in the reversible counter 20 is recorded (periods of the pulse signal of the reference frequency) corresponding to the duration of the time interval highlighted on the screen of the tube 4 with the appropriate Start and Stop marks (Fig. 3). The duration of this interval is equal to the difference between the duration of the auxiliary pulses from the output of the counting trigger 6 in the fourth and second cycles of operation of the device when the signal gates at the points marked with Stop and Start, respectively, (FIG. 2d). After setting the brightness marks on the boundaries of the time interval of interest, the numerical value of this interval appears on the digital indicator 23, which displays the number rewritten into register 21 from counter 20. Register 21 is necessary for a stable (flicker-free) display of the measurement result.

The digital information is entered into the register 21 by the overflow signal of the accumulation counter 22 (FIG. 2L), which counts the overflow signals from the mode counter 14 (FIG. 2k). The overflow signal from counter 14, mode a, appears at the end of each work cycle, and the overflow signal from accumulation counter 22 once per n work cycles, where n is the number of accumulations determined by the counter capacity 20. At the same time as entering information into the register 21, installation occurs counter 20 to the zero state and a new measurement is started.

The accumulation of the results of individual measurements in the reversible counter 20 makes it possible to reduce the frequency of the reference pulses produced by the generator 19j by a factor fn compared to the frequency that is necessary for carrying out single measurements when

condition of obtaining the same accuracy.

The highest accuracy of the proposed method of measuring the duration of time intervals allows obtaining in an oscilloscope with digital measurements, which is controlled by an embedded microprocessor. In this case, the amplitude of the signal under investigation is determined not by the oscilloscope screen, but directly from the array (set) of the instantaneous values of the signal under investigation in a digital code. The calculation of constant start and stop levels and the comparison of the instantaneous values of the signal under investigation with these levels is also carried out in digital form by a microprocessor. This makes it possible to eliminate the error of setting the time interval of interest associated with the nonlinearity of the vertical deflection amplifier, the nonlinearity of the vertical tube deflection system, the visual error of alignment across the tube screen, etc.

The constant Start and Stop levels, as well as the first and second values of the second sweep signal, are then stored in digital form in the microprocessor's RAM. The conversion of the stored values of the second sweep signal to analog is carried out using a separate digital-to-analog converter.

Determining the duration of the Stlrt and Stop auxiliary pulse signals, determining the duration of the time interval of interest by subtracting the duration of the Start signal from the Stop signal duration, converting the resulting code into a form suitable for indicating, for example, a binary decimal seven-segment code, and controlling the digital indicator It is programmed using a microprocessor. Thus, the microprocessor (together with the RAM, ROM and ADC and CDL units) replaces all the counters 7, 8, 14, 20, 22 and the register 21 (figure 1). Moreover, it is possible to conduct automatic and - from measurements, during which the microprocessor also performs the functions of resistors. Controls that perform the functions of resistors are needed only in manual measurement mode.

Claims (1)

Invention Formula An oscillographic method of measuring the temporal parameters of signals, comprising the steps of forming a sequence of clock pulses, forming a first clock synchronous with the clock pulses, and a second sweep signal, comparing these signals and generating strobe pulses at the moments of coinciding the instantaneous values of the first and second sweep signals, determining the amplitude of the 5 steps to signal by the set of its instantaneous values obtained by gating the signal under study, and determining two constant levels Start and Stop, corresponding to, for example, 0.1 and 0.9 amplitudes of the signal under study, comparing the instantaneous values of the signal under study with the Start and Stop levels and determining the measured time interval, limited by the recorded Start and Stop times, that, in order to improve the measurement accuracy of short time intervals, the fixation of the Start and Stop times is performed by memorizing the first and second values of the second sweep signal, at which the instantaneous values of the measured sig5 The currents are constant. Start and Stop, respectively, comparing the instantaneous values of the first sweep signal with the first and second stored values of the second sign of the sweep and fixing the time of their coincidence. P51 Fig.Z