SU1442923A1 - Time interval meter - Google Patents

Abstract

The invention relates to a measurement technique and can be used in oscilloscopes with a digital measurement of the duration of time intervals. The purpose of the invention is to improve the accuracy of measuring the duration of time intervals. Trigger 4

Description

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ff

4 HchE

tND

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9U2.1

alternately connects to the input of the sweep generator 7 or the output of the synchronization unit 2, or the output of the digital delay unit BZZ 3. In this case, two images of the signal under investigation are formed on the screen of the cathode-ray tube 10: one formed directly from the sync pulses, another formed with some delay, defined by BZZ 3. By combining with BZZ 3 both images, the coarse value of the measured interval is counted in the higher bits of the digital indicator (DI) 11. A more accurate value of the measured interval is obtained by the sensational method using an audio / video converter (DAL) 8, a key 12, a code generation unit 6. At the moments of switching on delayed sweeps to the second input of tract 9, horizontal 1

The invention relates to a measurement technique and can be used in electron beam oscillographs with digital measurement of the duration of time intervals.

The purpose of the invention is to improve the accuracy of measuring the duration of time intervals,

; FIG. 1 shows a block diagram of a meter 5 in FIG. 2, diagrams explaining its operation.

The meter contains a vertical deflection path 1, a synchronization block 2, a digital delay block 3, a trigger 4, a switch 5, a code generation unit 6, a sweep generator 7, a digital-to-analog converter 8 (D / A converter), a horizontal deflection path 9 of the cathode ray tube (CRT) 5 digital indicator 11, key 12.

The inputs of the vertical deviation path 1 and the synchronization unit 2 are connected to the source of the signal under study Uy, the output of the vertical deviation path 1 is connected to the first input of the CRT 10, the output of the switch 5 is connected to the input of the sweep generator

The output voltage of the DAC 8 is supplied to the maximum deviation and the image is combined with the accuracy determined by the discreteness of the DAC 8. The code corresponding to the output voltage of the DAC 8 is entered into the lower bits of the DI 11 and. determines the exact value of the measured interval. Introduction to the BCG device 3, trigger 4, code generation unit 6, key 12, DI 11, switch 5 reduces the measurement error of the time intervals, since both the combined signals pass through the same circuits, which eliminates errors due to drift horizontal deflection amplifier and sweep deflection factors. The meter also contains a path 1 vertical deviation of about 2 Il.

7, the output of which is connected to the first input of the horizontal deflection path 9, the output of which is connected to. the second input of the CRT, the input of the 3-digit digital delay unit is connected to the first output of the synchronization unit 2 and to the second input of the switch 5, the second output of the synchronization unit is connected to the counting input of the trigger 4, the first

0. the output of which is connected to the third input of the switch 5, the second output of the digital delay unit is connected to the first input of the digital indicator 1.1, the output of the code generation unit 6

5 is connected to the input of the DAC 8, the second output of the code-forming unit is connected to the second input of the digital indicator, the second output of the trigger 4 is connected to the control input of the key 12 connected between the output of the DAC 8 and the second input of the horizontal deflection path 9 connected to the first switch of switch 5.

5 The meter works as follows.

The investigated signal U, j; normalized using path 1 vertical

3

deviations and enters the vertically deflecting plates of the CRT 10. Simultaneously, the synchronization unit generates synchronization pulses that arrive at the first input of the switch 5 and then to the input of the sweep generator 7. The sweep signal is amplified by the horizontal deflection path 9 and is fed to the horizon. CRT deflection plates. 10. On the CRT screen, an image of the signal Uy under study is formed. Simultaneously, the signals from the second output of the synchronization unit are fed to the counting input of trigger 4. The latter alternately connects to the input of the generator 7 a sweep or the output of the synchronization unit 2, or the output of the digital delay unit 3. At the same time, two images are formed on the screen.

One signal is generated directly from the sync pulse (Fig. 2a5) image I and the second, formed with a certain delay, determined by the installation of the digital delay unit 3 (Fig. 2a, image II).

The measurement of the duration of the time intervals is performed in the following sequence. Let it be necessary to measure the duration of the interval

T; "between points 1

and

2 images of the I signal. The operator controls the oscilloscope on the CRT screen to display the image of the signal under investigation, which provides the maximum image of the interval T to be examined on the screen of the CRT. The operator then changes the delay T, j until the points 1 and 2 of images I and II match (Fig. 26). The delay value is set

bum

equal to the duration of the interval T

The measurement error is:

/five

Cg

SOVM

CH

{

 (de)

where hzs is the error of the digital delay;

 cuBw combination error, consisting of;

D - discrete digital delay,

f (df) g is the component defined by the width of the image line. In real conditions, without much difficulty, it is possible to achieve dc equal to (0.2-1)% th (25-100) not;

f (.

 H

The component of the alignment error due to the thickness of the line f (Lr) is reduced by reducing the width of the lines, increasing the geometric dimensions of the invention — by stretching ten times, setting the maximum possible size of the images I and II at the place of their combination (Fig. 2c ).

The registration error, determined by the discrete delay, is reduced by decreasing the launch delay discreteness. This way you can reduce the value of L to 20-50 no.

A further reduction in the combination error can be achieved by measuring time intervals T, not exceeding the value of / f, by the compensation method. This is achieved using a DAC 8, a key 12, a code generation unit 6. The key 12 operates synchronously with the switch 5 and is controlled from the trigger 4. At the moments when the delayed sweeps are turned on, the output of the DAC 8 is connected to the second input of the horizontal deviation path. When the output voltage of the DAC 8 changes, the image is moved from the delayed sweep within the delay increment, for example , in the range of 0-100 no. Due to this, it is possible to measure the KOMP by the sensation method with discreteness

t

and-

and - the number of DAC levels. With

 NA and 1 discrete not. The result of the measurement is displayed on the digital indicator 11. The code corresponding to the delay value t}. Is entered in the upper bits of the indicator, the DAC code 8 - in the lower bits.

In the device, the two combined signals pass through the same chains, therefore, the error due to the drift of the horizontal deflection amplifier is excluded. The magnitude of the delay does not depend on the sweep duration (with measured intervals longer than

55 discrete delay), therefore, the error is eliminated due to the error of the sweep deviation coefficients. This provides a reduction in measurement error.

Claims (1)

Invention Formula The time meter, containing a cathode ray tube, vertical and horizontal deflection paths, a synchronization unit, a sweep generator, and a digital-analog converter, with inputs of the vertical deflection path and synchronization unit connected to the source of the signal under investigation, the output of the vertical deflection path is connected to the first input of the electron beam tubes, generator output times-15 digital indicator, second output winding through the horizontal deflection path is connected to the second input of the cathode ray tube, characterized in that, in order to improve the accuracy of measuring time intervals, a digital delay unit, a trigger, a code generation unit, a key, a digital indicator, a switch, and an input ujOcHoSttoe image Ux (I) G Zader / nano 4 u ishrage niv and, (n) BUT / I B UK images with embedded x10 raster image The digital delay unit is connected to the first output of the synchronization unit and the second input of the switch, the second output of the synchronization unit is connected to the counting trigger input, the first output of which is connected to the third input of the switch, the second output of the digital delay unit is connected to the first input of the digital indicator, the output of the code generation unit connected to the input of a D / A converter; the second output of the code generation unit is connected to the second input the trigger is connected to the control input of the key connected between the output of the digital-to-analog converter and the second input of the horizontal deviation path; the first output of the digital delay unit is connected to the first input of the switch, the output of which is connected to the input of the unwrapped generator BUT / I WITH