JPH0644014B2 - Scanning oscilloscope trigger method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a trigger activation method for making a sweep repetition period in a scanning period highly stable and highly accurate in a scanning oscilloscope.

"Oscilloscope" means a well-known oscilloscope that displays one sweep bright line and starts sweeping with a trigger signal to observe the waveform in order to freeze the waveform. Since the multi-waveform display, etc., is basically an observation and operation mode by one sweep bright line, hereinafter, these are collectively referred to simply as “oscilloscope”. The "scan" means that the scanning state is achieved by repeating the sweep while changing the vertical position each time the sweep ends due to the step wave. A waveform observing device for observing a waveform by such scanning is called a scanning oscilloscope. Since the vertical position is changed by the staircase wave, it is always parallel to the horizontal axis even if the step interval is changed, and this does not mean "scanning" well known in television receivers and the like.
The "scanning line" is one of the sweeping bright lines in scanning and is called a "scanning line", and includes a curve because a waveform is displayed. The surface displayed by the scanning lines is referred to as a "scanning surface", and the waveform observed by this scanning surface is referred to as a "planar observation waveform". When the number of scanning lines is small, for example, when the number of scanning lines is two, it does not form a "plane", but it is used to distinguish it from the observed waveform of the oscilloscope. In addition, in the case where it is clearly shown or explained by the drawing or when it is not necessary to distinguish it, it is also simply referred to as "observation waveform". In addition, it is assumed that the scanning line in the example of the planar observation waveform in this figure is the first scanning line at the upper position, and the scanning is performed while sequentially changing the display position in the downward direction. In the present invention, these are used as meanings as described above to avoid confusion with well-known terms and to clarify the present invention.

FIG. 1 is a block diagram showing a basic configuration example of a scanning oscilloscope in which the present invention is implemented. In this structure, the present invention is carried out at the position indicated by the one-dot chain line frame (117). Before describing the present invention, the operation of the scanning oscilloscope will be described in order to clarify the present invention. Since the present invention will be described with reference to FIG. 2 and subsequent figures, the configuration of the one-dot chain line frame of (117) is removed ((105) is a trigger switching unit, and (131) is a counting pulse generating unit).
The description will be made assuming that the route (113) is connected.
Reference numeral (101) is a vertical amplification unit, and the observed waveform (112) is input from the input terminal of (111). Reference numeral (104) is a trigger shaping unit, and a trigger signal (123) is routed from a waveform (122) output from the vertical amplification unit (101) to a route (113).
Output to. Sweep part trigger signal of (106) (123)
Start sweep with, and this sweep wave (124) is route (121)
Is output to the horizontal part of (108). Horizontal part (10
8) amplifies the sweep wave applied to the horizontal deflection plate of the cathode ray tube (110) to an amplitude that can move the bright spot from the left end to the right end of the normal display surface. The bright spot moves in proportion to the time, and the moving speed is in a wide range depending on the measurer.
It can be set in 6). In addition, the sweep unit (10
Using the blanking signal (125) obtained in 6), the staircase wave (126) is shaped in the staircase portion (107) every time the sweep is completed. This staircase wave is output to the path (115) and added to the addition unit (1
02) the waveform (1
22) and outputs the waveform (127) to the path (120). This waveform is amplified by the vertical output section (103) and applied to the vertical deflection plate of the cathode ray tube. Generally, the above operation is performed and displayed while changing the vertical position for each sweep like the observed waveform (128). An observed waveform example (129)
To get These are well-known oscilloscope techniques as well as well-known scanning oscilloscope techniques. In this case, since each scanning line is activated by the trigger signal (123) for each sweep,
For repetitive waveforms such as waveform (122), the observed waveform example (1
The same waveform is displayed as in (29), and even if there is a missing pulse or a time shift (phase, pulse width, etc.) in the portion (130), the trigger signal will follow it. , In the display method like the observation waveform example (129),
It will not be observable. Usually, in order to observe such an abnormal waveform, it is necessary to use an external trigger or to compare it with a waveform that does not have any abnormalities, but if the frequency of occurrence is low,
Difficulty occurs when there is little time lag. If the delay sweep section is provided in the configuration of FIG. 1, partial enlargement becomes possible. Since this delay waveform is also the delay from the trigger sweep start point of each scanning line, it follows the trigger signal (123). It is the same even if the delay time is digitally stabilized. In this case, since the counting is started by the trigger signal (123), the timing difference from the counting clock signal causes
The start of the delayed sweep is irregular in the width corresponding to the clock width, that is, with counting jitter. Therefore, it is impossible to discriminate whether the waveform is due to the observed waveform when the waveforms of the upper and lower scanning lines are deviated to the left and right by performing the enlarged observation such that the counting jitter appears. In this way, when the trigger activation sweep is performed for each scanning line, a partial portion is displayed on each scanning line, and the waveform cannot be displayed continuously. In the scanning oscilloscope, the above scanning method is used, and the first scanning line is swept by the trigger signal, and subsequent scanning lines are swept continuously by scanning the sweep circuit regardless of the trigger input. This method is known, and in this scanning method, since the waveform is continuously displayed on each scanning line, the above-mentioned waveform omission, time lag, etc. are directly displayed on the scanning line. However, in this case, since the next sweep is started after the sweep is completed, the time from the start of the sweep to the start of the next sweep depends on the resistor such as the sweep circuit and the hold-off circuit, the capacitor, and the element such as the semiconductor. High stability cannot be achieved. When the sweep is repeated and the waveform is continuously displayed on the scanning line, even a slight variation affects the observed waveform. For example, when the number of scanning lines is large, a slight change of one scanning line is accumulated and becomes large at the final scanning line, and a slight variation is magnified by magnifying observation. These appear as jitter in the observed waveform and cannot be distinguished from the observed waveform. On the contrary, it is difficult to adjust the repetition time slightly.

The above will be described in detail with reference to FIG. It is well known that an observation waveform such as (201) can be obtained by observing a rectangular wave with jitter with an oscilloscope. In this observation, since the jitter from the trigger start point is displayed, the trigger start point includes the jitter. In this case, the jitter amount is not based on time. It is also well known that the vertical position can be changed for each sweep and the crossing component can be observed as in (202).
Is the jitter width from the trigger start point. It is also well known that when the jitter width is small, it can be delayed for a certain time from the trigger start point, that is, partially expanded by delay sweep, and the delay amount can be made stable and character by the counting pulse counting the reference pulse. As described above, this count pulse randomly includes count jitter for each sweep, and thus this becomes like the observed waveform of (202), which cannot be distinguished from the jitter of the observed waveform. Obviously, when a clock signal is used as a reference pulse in the waveform observation of a pulse circuit or the like, the counting jitter disappears, but at the same time, the jitter of the waveform itself cannot be observed (since the waveform follows the clock signal).

In the scanning oscilloscope, the trigger-activated scanning method that activates and scans each scanning line includes the method of activating and sweeping the observed waveform for each scanning line as described above, and the method of activating and sweeping only the first scanning line with the observed waveform. It is well known that there is a method of scanning subsequent scanning lines irrespective of the waveform to be observed, which is also illustrated in Japanese Patent Laid-Open No. 56-188690 as an example. The present invention relates to the latter, but since the two types of schemes described above are related, the two basic trigger-triggered scanning schemes described above will be described for clarity of the invention. Therefore, these operations will be described for the case of observing the waveform of the pulse waveform (204) pulse-width modulated with the waveform (206). However, it is assumed that the respective waveforms are synchronized. In the former case, the trigger signal is taken out from the waveform (204) because the starting sweep is performed for each scanning line, and the sweep wave of (207) is obtained, and the observed waveform (226) is obtained by scanning with the step wave of (210). At this time, the trigger point is (21
As shown by the triangle mark in 6), it is provided for each scanning line (22
In order to make the observed waveform of 6) stationary, if the number of trigger repetitions of the observed waveform and the number of scanning lines do not match or are in a multiple relationship, they flow vertically as in (217). Further, since there is a trigger point for each scanning line, which trigger line is used to start scanning is indefinite, and therefore the observation state like the observation waveform of (226) does not always stand still. However, since the means for surely stopping the movement is disclosed in JP-A-56-188690, it is possible to always obtain the observed waveform of (226). Note that, as described above, this method corresponds to the well-known oscilloscope observation means in terms of trigger activation. In the latter, the sweep signal (212) is activated at the time of (211) when the trigger signal is taken out from the modulated wave (206) and the trigger level is set to (205) in order to make the planar observed waveform stationary. At this time, if the sweep time is set to (214), the staircase wave becomes like (213), and the observed waveform of (219) is obtained. The trigger start point is the position of the triangle mark of (215), and the scanning start point is the position of the triangle mark of (218). In this way, since the starting point of the trigger activation scanning is fixed at (218), the sweep time can be changed to move the waveforms on the second and subsequent scanning lines to the left and right, and the number of scanning lines can be set freely. Since the trigger point is fixed at the first point, it does not flow up and down, and in the above-mentioned jitter observation, each change amount can be observed in a plane based on one trigger start point. When the trigger level is changed, the planar observation waveform moves to the left and right as a whole, but stops at the trigger point. In the former, each scan line is triggered by the observed waveform, so the waveform on each scan line depends on the observed waveform, but in the latter, the sweep time (214)
Depends on. However, since the sweep times (214) (223) vary depending on fluctuations of circuit elements such as capacitors, resistors and semiconductors, noise and other contamination from peripheral circuits, operating environment such as temperature, etc., each scanning line is accurate. In addition, it is not possible to stably start with the isochronous time, and when the observation is performed as shown in (222) after the enlarged observation, it cannot be discriminated whether it is due to the observed waveform or the measuring instrument itself. For example, if the sweep repetition period, that is, the scanning period becomes unstable, the observed waveform that should be observed as in (221) is observed with jitter as in (219). Since (228) is drawn by paying attention to the changing state of the falling edge, it becomes impossible to accurately observe the illustrated waveform indicating that there is jitter. Therefore, when trying to achieve stable and high accuracy by the well-known counting circuit,
In the former method, the trigger is activated for each scanning line, so the sweep wave (2) with a stable and highly accurate delay amount in (208) is used.
09), it is impossible to stabilize the scanning cycle which is the object of the present invention. Further, when the observation is expanded, the counting jitter of (220) appears. Of course, depending on the amount of delay, the trigger signal may be skipped and the same period cannot be displayed, so that the planar observation waveform flows vertically and is deformed. Further, in the latter, since the trigger signal during the scanning period is not accepted, only the trigger start point can be delayed. That is (22
A phenomenon occurs at the time of 4), and the sweep is started after the time of (225) has elapsed. Even if the time is made stable and the accuracy is high, the planar observed waveform only moves to the left and right as a whole. Since the present invention is intended to stabilize the scanning period of the latter by using the former trigger-activated scanning method, in order to fix the trigger point to the first scanning line, the first scanning line is the waveform to be observed. The start-up sweep is performed by the following scanning line, and the subsequent scanning line is intended to make the repetition period of the sweep after the trigger point highly accurate and highly stable by performing the start-up sweep by the counting pulse that counts the highly stable pulse.
As described above, this operation triggers scanning by the former method, but the latter scanning state occurs on the scanning surface. Therefore, starting the sweep of each scanning line after the trigger start point, that is, during the scanning period is started by the continuous counting pulse without counting jitter, so that only the modulation component of the observed waveform is stopped like the observed waveform of (221). It will be possible to observe. Since the counting jitter is also eliminated, only the modulated component can be accurately observed even when magnified observation is performed. Further, as described above, the trigger point is fixed at the position of the triangle mark of (215), so the sweep time, that is, the count value of the count pulse is changed to move left and right while the waveforms on the second and subsequent scanning lines are stationary. You will be able to do it. For example, stable and accurate observation and scanning can be performed when the rising portion of the pulse is displayed while being slightly shifted, or when waveforms at different times are displayed on the upper and lower scanning lines for comparison. In the jitter observation (21
It becomes possible to observe based on the trigger start point of 1).
That is, the amount of change can be displayed with high stability and high accuracy with respect to the reference time (227). As mentioned above, the well-known oscilloscope displays the amount of change from the trigger point.
In this way, it is impossible to display the variation with respect to the reference time even if the observation waveforms are crossed. As described above, in the past, stable surface observation was difficult when the number of scanning lines was large, and accurate surface observation was difficult in magnifying observation because the variation in the time difference between the upper and lower scanning lines was also enlarged. It enables stable and highly accurate waveform observation.
Therefore, one object of the present invention is to provide an observing means corresponding to the latter trigger activated scanning method with high accuracy and high stability.

Another object of the present invention is to provide a scanning oscilloscope characterized by being capable of observing a waveform by making a planar observation waveform stationary on a highly stable and highly accurate scanning surface by the above-mentioned means.

Another object of the present invention is to read time with high accuracy over all scanning lines.

Another object of the present invention is to display a minute frequency change or time difference in real time and read it with high accuracy.

Still another object of the present invention is to control the sweep start time of each scanning line with high accuracy.

Other objects and advantages of the invention will be apparent to those skilled in the art from the following detailed description of the preferred embodiments of the invention. Furthermore, the following examples do not disclose and limit the present invention in its entirety, but are merely for those skilled in the art to fully understand the principles and applications of the present invention, and those skilled in the art can make various changes and modifications as appropriate. It will be understood what can be done.

FIG. 2 shows an embodiment of the present invention. This is the first
In the figure, it is carried out at the position indicated by the one-dot chain line frame (117). Therefore, in the following description, it is assumed that the path (113) in FIG. 1 is removed and the configuration of the trigger switching section (105) and the counting pulse generating section (131) is added, and the waveform progress chart is shown in FIG. Also, description will be made with reference to FIG.
(1) is a trigger forming part, which is the same as (104) in FIG.
(6) is the sweep section, which is the same as (106) in FIG. 1, and (5) is the staircase section, which is the same as (107) in FIG. As described above, the waveform (20) to be observed is input to the terminal (9), and the trigger signal (21) is passed through the trigger shaping section (1) and route (12).
Appears. The trigger shaping section (1) is a well-known oscilloscope technology. Switches (2) and (4) are alternately turned on / off by an inverter (3). Since this switch may have a high switching path and a low switching speed, it is well known such as a logic IC or a MOS-IC, but it is shown in FIG. The input is (69), the output is (70) (either one is acceptable), and the switching signal is (7
Input from 1). It turns on when (71) is a positive potential.
This is a well-known circuit technology. The sweep section of (6) starts the sweep by the trigger signal, and the sweep wave (22) is fed to the terminal (11).
To the horizontal axis as described above. This sweep section (6)
Is a well-known oscilloscope technology. Blanking signal (2
5) is added to the step section (5) and the step wave is set to 1 at the end of each sweep.
When the steps are modeled and the set number of steps is modeled, the process returns and repeats. The step wave (23) is output to the terminal (10) to change the vertical position for each sweep as described above. This step portion is a well-known and well-known circuit technique, but is shown in FIG. 5 as an embodiment. The blanking signal is input to the terminal (60), the staircase wave is shaped by the pulse of (61), and is reset when the stylus wave is shaped to a certain potential, and the staircase wave is output to the terminal (66). The variable resistor (62) changes the amplitude of (61) to adjust the number of steps. The flip-flop is inverted by the retrace pulse (63) (retrace erase signal) of the first sweep wave, and is restored by the reset pulse (64) that finishes the formation of the staircase wave and returns to the original potential (waveform ( 65) is obtained and output to the terminal (67), and becomes the waveform (26) of the path (13). This is a well-known circuit technology. (7) is a NAND gate which synthesizes the waveform (25) and the waveform (26) to obtain the waveform (27). Waveform (2
Since the rising edge of 5) and the falling edge of the waveform (26) are at the same timing, the rising edge of the waveform (25) is delayed when a pulse drop occurs. Hereinafter, this composite waveform (27) is simply referred to as "control signal". In (8), a counting pulse having a numerical value arbitrarily set by the counting unit is output to the path (16). This counter uses a stable clock signal (28) such as a crystal oscillator.
Is counted. ((49) indicates that this clock signal is a pulse). When the control signal has a zero potential, it is in the clear state, and when the control signal has a positive potential, the counting pulse (29) is continuously output. This is a well-known counting circuit technique, but it is shown in FIG. 7 as an embodiment. (82) is a counter, (8
3) is a matching circuit, and (84) is a setting switch, which continuously outputs counting pulses of 4 digits or less to (81). Count ON
/ OFF is performed by the control signal from (80). This is a well-known counting circuit that clears and repeats when the count values match.
When the staircase wave (23) has not been formed yet and has not been swept, the control signal is at zero potential, so the switch (2) is turned on at a positive potential, and the trigger signal of (21) is the sweep section (6).
Entered in. At this time, the counting unit (8) is in the clear state. At time (24), the sweep circuit is activated by the trigger signal (21). At the same time, the control signal becomes positive potential,
The counting unit (8) starts counting and the switch (2) turns off.
F, the switch (4) is turned on, and the trigger signal to the sweep section is switched to the counting pulse (29) from the path (16).
The display period in the first sweep of (37) is (30), and since the staircase wave is not formed at this time, the observed waveform of (39) is obtained. When the sweep is completed, one step wave is formed and the sweep circuit enters the waiting state. The waiting trigger signal is the counting pulse (29). When the counting of the set numerical value is completed, the counting pulse (43) is output and the switch (4) turned on
And the second sweep starts. The display period in the second sweep of (38) is (31), and the staircase wave is 1 at this time.
Since it is a step model, the observed waveform is (40). Similarly, the third and fourth sweeps are started with counting pulses (44) and (45), and the observed waveforms are (41) and (42). When the staircase wave is completed, the control signal becomes zero potential and the switch (2)
Is ON and the switch (4) is OFF, and the trigger signal to the sweep section is switched to the trigger signal (21) from the path (12). Further, the counting unit (8) is cleared and returns to the original waiting state. At the time of (46) when the trigger signal of (21) arrives, the above operation is repeated. In this way, the observed waveform (47) is obtained. If the second sweep start of this waveform is shifted by (34) with respect to the trigger signal (21), it will be accumulated as (35) at the third time and (36) at the fourth time. (32) is a sweep wave when the sweep pulse is set at the set value and the sweep time is shortened. Each display waveform is (33) and the observed waveform is (48). If the sweep speed is increased in this way, the deviation will be enlarged.
Since (43), (44), and (45) are counting pulses, there is no counting jitter as described above, so that it is possible to observe only the change state of the observed waveform even when magnified observation is performed. However, at (24) and (46) at the start of the first sweep, the trigger signal (2
Since it is activated by 1) to start counting, counting jitter occurs only at this time.

FIG. 4 is a waveform progress chart and an example of observed waveforms for explaining the operation of frequency measurement or frequency calibration (adjustment). (54) indicates that it was omitted in the middle. The observed waveform is (50), which is an unknown frequency. By the same operation as described above, the sweep of the first scanning line is started by the trigger signal of the observed waveform (50), and the sweep for the subsequent scanning lines is swept by the counting pulse (51) to obtain the sweep wave (52). , Create stairs (53). If the number of steps is 23, the number of scanning lines is 23 (here, this number has no meaning). Since the falling portion of the observed waveform (55) is parallel to the Y axis, the time shift of (57) is zero. Also, since one cycle of one scanning line is observed, it means that the cycle of the counting pulse at this time matches the cycle of the waveform to be observed (50). Therefore, the count set value is read and the reciprocal is obtained. For example, the frequency of the observed waveform (50) can be known. As mentioned above, (5
The time shift of 7) increases as the number of scanning lines increases or as the sweep time becomes faster, so the number of scanning lines increases or the sweep time becomes faster so that the trailing edge becomes parallel to the Y-axis. By changing the numerical setting value to, it becomes possible to know the frequency with higher accuracy. In addition, when adjusting the oscillation frequency of the oscillator circuit to a desired frequency, the period is obtained by the reciprocal of the desired frequency, the numerical value is set, and then the oscillation waveform is observed and the observation waveform (55) is obtained. If you do, it will be the frequency you want. In order to improve the adjustment accuracy, it is advisable to increase the number of scanning lines or partially enlarge the same as described above. In this frequency adjustment, the most different point from the method using the frequency counter is that it can be adjusted in real time. Incidentally, when the time difference is as shown in (57), the observed waveform is as shown in (56).

As described above, according to the present invention, the repeating cycle of the sweep can be made highly accurate and highly stable, so that minute jitter can be faithfully observed. In addition, stable waveform observation can be performed even when magnified observation or the number of scanning lines is large. Further, since each scanning line continues its time, there is an effect that the time can be accurately read over a plurality of scanning lines.

As described above, according to the present invention, the first scanning line starts sweeping with the trigger signal from the observed waveform, the second and subsequent scanning lines start sweeping with the counting pulse, and the final scanning line sweeping ends. Then, the sweep signal is returned to the original state in which the sweep is started by the trigger signal from the waveform to be observed and repeated, and therefore various modifications and variations can be made in the implementation without departing from the gist of the present invention. For example, if the circuit is such that the waveform (27) can be extracted directly from the stairs, etc.
AND (7) is unnecessary. Further, the counting section is also variously modified depending on the counter used, such as a preset counter. Furthermore, as described above, the trigger signal to the sweep circuit is
The position and circuit in FIG. 2 are not limited as long as the same operation as the switching operation can be performed.

[Brief description of drawings]

FIG. 1 is a basic block diagram of a scanning oscilloscope in which the present invention is implemented. FIG. 2 is an example of a schematic circuit diagram of the trigger controller of the present invention. 3 and 4 are waveform charts and examples of observed waveforms for explaining the operation principle of the present invention. FIG. 5 shows an example of a well-known simplified staircase wave generation circuit, showing the connection relationship with the present invention. FIG. 6 shows an example of a known switch circuit, which is an embodiment of switches (2) and (4). FIG. 7 shows an example of a simple counting circuit. FIG. 8 is an example of an observed waveform and an example of a waveform progress chart for comparing and explaining the known operation and characteristics of the present invention. In the figure, (1) is a trigger forming part, (2) and (4) are switches, (3) is an inverter, (5) is a stair part,
(6) is a sweep unit, (7) is a NAND gate, (8) is a counting unit, (9) is an input terminal of the observed waveform for triggering, (1
0) is a staircase wave output terminal, (11) is a swept wave output terminal, (12) is a trigger signal path of an observed waveform, (1)
3) is the signal path of the pulse or waveform (26) during the staircase shaping period, (14) is the path of the blanking signal of the sweep wave,
(15) is a control signal path, (16) is a counting pulse path which is a trigger signal, (20) is an observed waveform, (21)
Is the trigger signal generated by the observed waveform, (22)
Is a sweep wave, (23) is a staircase wave, (24) and (46) are scan start times, (25) is a blanking signal, (26) is a pulse during the staircase shaping period, and (27) is control. Signal, (2
8) is a clock signal, (29) is a waveform of counting pulses, (43) is the first counting (44), the second (45) is the third counting pulse, and (47) and (48) are surfaces according to the present invention. Example of dynamic observation waveform, (50) waveform to be observed, (51) counting pulse, (52) sweeping wave, (53) staircase wave, (5
5) (56) is an example of a planar observation waveform according to the present invention, (10)
1) is a vertical abdomen section, (102) is an addition section, (103) is a vertical output section, (104) is a trigger shaping section, (105) is a trigger switching section, (107) is a staircase section, and (108) is horizontal. Section, (110) is a cathode ray tube, (111) is a vertical axis input terminal, (113) is a temporary signal passage path for explaining the operating principle of the scanning oscilloscope, and (114) is a staircase wave during the modeling period. The pulse path corresponds to the path (13), (116) corresponds to the blanking signal path and corresponds to the path (14), and (117) is the basic scanning configured in the block diagram example of FIG. Shows a typical implementation site in which the present invention is implemented in a scanning oscilloscope. (118) is the path of the blanking signal, (119) is the scan start time, (131)
Indicates a counting pulse generator.

Claims (1)

[Claims] 1. A trigger circuit that forms a trigger signal according to an observed waveform, a sweep circuit that is activated by the trigger signal, and a staircase wave generation circuit that generates a staircase wave at each sweep end.
A switching circuit that can switch the trigger circuit to the sweep circuit and the counting circuit that counts the reference pulse and can continuously generate the count pulse that becomes the trigger signal to the sweep circuit at the count value that can be set arbitrarily during the scanning period. And a sweeping for the first scanning line is started by a trigger signal obtained from the trigger circuit, at the same time counting of the counting circuit is started, and the trigger signal to the sweeping circuit is switched to the counting pulse. When the sweep for the first scanning line is completed, the staircase wave is formed by one step, the vertical position is changed, the second sweep is waited, and the second and subsequent sweeps are swept by the above-mentioned counting pulse that has been switched. When the sweep of the last scanning line is repeated, the sweep position of the first scanning line is returned to, and the trigger signal to the sweep circuit is also switched to the trigger signal from the trigger circuit. Then, after that, similarly, the trigger signal based on the observed waveform is activated and the above-described operation is repeated. In this way, the trigger signal based on the observed waveform is used to start the first sweep and counting, and the second and subsequent times with the counting pulse. The method includes a means for stationary and highly accurate and highly stable scanning of the surface observation waveform by starting the sweep of the scanning line, and the means having the above-mentioned configuration enables the surface observation waveform to be obtained on the highly accurate and highly stable scanning surface. A scanning oscilloscope characterized by being able to stand still and observe waveforms.