JPH10206225A - Method for counting wave number and vibration-measuring apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a wave number accurately even when an input signal includes noises. SOLUTION: According to the method, an upper and a lower envelope lines of an input signal measured at a measurement step S1 are detected (S2). Based on the upper and lower envelope lines, a nearly intermediate level of the envelope lines is extracted as an intermediate line (S3). Then, an area formed for every one wave above or below the intermediate line by the intermediate line and an input signal waveform measured at the measurement step S1 is calculated for every wave (S4). When the area is larger than a preset area, one wave of the area is specified as an effective waveform to be counted (S5). A count of intersections of the specified waveform and a predetermined reference value is counted in accordance with a detection time of the waveform (S6).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wave number counting method, and more particularly to a wave number counting method used in digital signal processing in the field of measurement. Further, the present invention relates to a vibration measuring device, and more particularly, to a vibration measuring device for measuring a vibration of an object in a non-contact manner, which is a basis for structural analysis of the object.

[0002] A vibration measuring device is used not only for measuring noise and body characteristics of an engine, a body, a door, a window, a muffler, etc., but also for detecting abnormal vibration of a processing machine such as a drill and a cutting tool. It also includes various other objects that require vibration analysis.

[0003] The wave number counting method can be used for a device for counting the wave number using a threshold value or a device for measuring time. For example, it is used for the measurement of the flight time of an ultrasonic wave in ultrasonic distance measurement, the wave number measurement of an optical interference distance meter, and the wavelength measurement counter used in frequency measurement.

[0004]

2. Description of the Related Art Hitherto, vibration measurement of a vehicle body has been performed by an acceleration pickup installed on an object or a moire vibrometer using slit light. The vibration of the object measured by the vibration measuring device is used for vibration analysis of the object.
By analyzing the structure of the object based on the amplitude at the resonance frequency, determination of the rigidity of the object to be measured (for example, determination of the quality of welding) is performed.

[0005] Abnormal vibration detection of a processing machine such as a drill motor is performed by detecting a change in the drive current of the motor or by AE.
(Acoustic Emission) to detect the impact noise, and also by a pickup sensor installed via a mounting jig.

[0006]

However, since the acceleration pickup is of a contact type, the weight of the sensor and the connecting cable influences the vibration, so that accurate measurement becomes difficult. Further, the moiré vibrometer can determine the overall vibration tendency but cannot measure the displacement of the vibration of the object.

[0007] In addition, in the measurement of vibration of a processing machine such as a motor, it is difficult to perform retrofitting by detecting a change in driving current of the motor, and it is difficult to detect when the drill diameter is 3 mm or less.
For this reason, it is difficult to detect the lack of the gear of the motor by comparing the result with the vibration analysis result of the normal object, and in particular, it is not possible to perform the abnormality determination by the vibration measurement device and the vibration analysis device with a small motor. there were.

[0008] Further, the detection by the impact sound is to detect the impact sound with broken teeth, but there is a disadvantage that the apparatus is expensive, the influence of the ambient noise is easy, and the detection of the impact sound is difficult. Furthermore, conditions are severe such that a flat surface is desired for the surface to be brought into contact with the pickup microphone.

In addition, the vibration characteristics change due to the weight of the sensor and the cable, and the abnormal vibration detection condition changes at the position where the sensor is mounted. Therefore, the structure of the object cannot be stably and well analyzed. For this reason, a non-contact vibration measuring device is desired, but a non-contact vibration measuring device that measures even the displacement of vibration is not known.

[0010] Further, since the object of vibration measurement from the vehicle body to the small motor is wide, and it is desired that the quality inspection of welding and the quality inspection of the processing machine be incorporated into the manufacturing process, the vibration measurement device is also compactly installed. However, it is desirable to use an easy and inexpensive one.

For this purpose, the applicant has a light detecting means for observing a laser beam reflected from an object to be measured, a signal processing means for analyzing a waveform signal output from the light detecting means and detecting a sawtooth wave. Calculating means for calculating the switching time of the vibration direction of the measuring object based on the wavelength difference for each sawtooth wave detected by the signal processing means, and the switching time information calculated by the calculating means. A vibration measuring device including a data converting means for converting the wavelength of each sawtooth wave into displacement data of the object has been developed and has already been filed (Japanese Patent Application No. 8-185576).

As shown in FIG. 10, the signal processing means detects a sawtooth wave d corresponding to the displacement b of the vibration surface a of the object to be measured. One sawtooth wave is generated when the vibrating surface is displaced by a distance (λ / 2) of a half of the laser wavelength. Therefore, when the wave number of the sawtooth wave is counted, the displacement of the measurement object can be measured.

However, in the method of measuring the displacement of the object to be measured by counting the sawtooth wave, as shown in FIG. 11, the sawtooth wave is generated by temperature drift of a photodiode or an amplifier for photoelectrically converting a laser or electromagnetic induction. May fluctuate (indicated by the two-dot chain line indicated by the symbol n in FIG. 11). At this time, the position at which the wave number is counted in the sawtooth waveform is not constant, so that the measured vibration displacement becomes inaccurate. Further, when the center voltage level of the sawtooth wave greatly exceeds the ground level, the sawtooth waveform does not cross the ground level, and the wave number is not counted.

When the moving direction of the vibrating surface changes, the moving speed approaches zero and the waveform is extended. As shown in FIG. 12, if noise is added in a state where the waveform is extended, the number of waves is erroneously counted when crossing the ground (a two-dot chain line portion indicated by a symbol n in FIG. 12).

[0015]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a wave number counting method capable of improving the inconvenience of the conventional example and, more particularly, providing a wave number counting method capable of accurately measuring a wave number even if an input signal contains noise. Aim. Still another object of the present invention is to provide a vibration measuring device that can accurately measure the vibration of a measurement object in a non-contact manner even if an input signal contains noise.

[0016]

Therefore, according to the first aspect of the present invention, there is provided a measuring step of measuring a change amount of an input signal inputted from a measuring object via various media, and a measuring step of measuring the amount of change in the measuring step. Counting the number of intersections between the waveform and a predetermined reference value in accordance with the reception time of the waveform. Moreover, after the measuring step and before the crossing counting step, an envelope detecting step of detecting upper and lower envelopes of the input signal measured in the measuring step, and an upper and lower envelope detected by the envelope detecting step. An intermediate line extracting step of extracting a substantially intermediate level of the envelope as an intermediate line based on the line, and the intermediate line extracted by the intermediate line extracting step and the input signal waveform measured in the measurement step, and An area calculating step of calculating an area formed for each wave on the upper or lower part for each wave, and counting an wave of the area when the area calculated by the area calculating step is larger than a predetermined area. There is provided a waveform specifying step of specifying a valid waveform of the object. The number-of-intersections counting step counts when the intermediate line extracted in the intermediate line extracting step and the waveform specified in the waveform specifying step cross in the upward or downward direction. This aims to achieve the above-mentioned object.

In the waveform counting method according to the first aspect, after the envelope is extracted in the envelope extracting step, an intermediate line at an intermediate level of the envelope is calculated. Further, in the area calculating step, an upper part (FIG. 4A) or a lower part (FIG. 4B) formed by the intermediate line and the input waveform signal is calculated. Then, the waveform specifying step discards a waveform having an area smaller than a predetermined area, and specifies only a waveform having an area larger than the threshold area as a valid waveform. For this reason, the number-of-crossings counting step counts (counts up) the wave number while removing the influence of noise.

According to the second aspect of the present invention, the light detecting means for observing the laser light reflected from the object to be measured, and the waveform signal outputted from the light detecting means is analyzed and a predetermined effective sawtooth wave is detected. And a displacement data generating means for generating displacement data of the object to be measured in accordance with a wavelength of each sawtooth wave detected by the signal processing means. In addition, the signal processing means detects an upper and lower envelope of the sawtooth wave, and intermediates the substantially intermediate level of the envelope based on the upper and lower envelopes detected by the envelope detector. An intermediate line extracting unit that extracts a line, an area calculating unit that calculates an upper or lower area formed by the intermediate line and the sawtooth wave extracted by the intermediate line extracting unit for each wave, When the area calculated by the area calculating unit is larger than a predetermined area, a sawtooth wave specifying unit that specifies a wave having the area as an effective sawtooth wave is provided.

In the vibration measuring apparatus according to the second aspect, the sawtooth wave specifying unit discards the sawtooth wave whose area calculated by the area calculation unit is equal to or smaller than a predetermined area, and equals or exceeds the predetermined area. Is specified as a counting target.
Further, the displacement data generating means obtains the displacement of the measuring object based on the wavelength of the sawtooth wave specified by the sawtooth wave specifying unit.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart showing the configuration of the wave number counting method according to the present invention. The wave number counting method includes a measurement step S1 for measuring a change amount of an input signal input from a measurement target via various media, and an envelope detection for detecting an upper and lower envelope of the input signal measured in the measurement step S1. Step S2 and an intermediate line extracting step S3 of extracting a substantially intermediate level of the envelope as an intermediate line based on the upper and lower envelopes detected in the envelope detecting step S2.

Further, the area formed for each wave above or below the intermediate line by the intermediate line extracted in the intermediate line extracting step S3 and the input signal waveform measured in the measuring step S1 is defined for each wave. An area calculating step for calculating, and S4, and a waveform specifying step S5 for specifying, when the area calculated in the area calculating step S4 is larger than a predetermined area, one wave of the area as a valid waveform to be counted. ing.

Then, the number of intersections between the waveform specified in the waveform specifying step S5 and a predetermined reference value is counted (counted) according to the reception time of the waveform.
It has. This intersection number counting step S6 includes the intermediate line extracted in the intermediate line extracting step S3 and the waveform specifying step S5.
Is counted up when the waveform specified in the above crosses upward or downward.

FIG. 2 is an explanatory diagram showing an example of a waveform to be subjected to wave number counting. The operation of each step shown in FIG. 1 will be described with reference to FIG. The measurement step S1 converts a measurement amount input from various objects such as radio waves, light waves, and sound waves from a measurement target into an electric signal and outputs the electric signal. As shown in FIG.
In the present embodiment, a signal in which the electric signal (input signal k) becomes a sawtooth wave is to be counted. In the present embodiment, the input signal k measured S1 in the measurement process is amplified and converted into digital data.

Next, an envelope extraction step S2 extracts an envelope h of the input signal k. This envelope h is generated at the top and bottom of the input signal k. Further, in the intermediate line extracting step S3, a value of a substantially intermediate level of the envelope h is calculated at regular time intervals, and is set as an intermediate line c. Further, in the area calculating step S4, the area of the hatched portion shown in FIG. 2 is calculated in order to calculate the upper area here.

Further, in the waveform specifying step S5, it is determined whether or not the area of each wave is equal to or more than a predetermined fixed area, and a waveform having a certain area or more is set as a waveform to be counted. Then, regarding the two-dot chain line portion indicated by the reference numeral n in FIG. 2, the narrow waveform on the right side is not treated as a waveform because the area is equal to or less than a certain value. At this time, in the waveform specifying step S5, the wavelength of the discarded waveform portion is divided into two and added to the wavelength of one wave before and after that.

After removing the influence of the noise portion as described above, the number-of-crossings counting step S6 includes a waveform specifying step S5.
Then, the number of intersections between the wave specified in step 1 and the intermediate line c is counted. As described above, according to the first embodiment, even if the waveform includes a noise component as shown in FIG. 2 and a voltage level fluctuates, the wave number can be effectively counted by digital signal processing. , The accuracy of various measurements and image processing can be greatly increased.

[Second Embodiment] FIG. 3 is a block diagram showing the configuration of the vibration measuring device according to the present embodiment. As shown in FIG. 3, the vibration measuring device includes a light detecting unit 10 for observing a laser beam reflected from an object to be measured, and a light detecting unit 1
A signal processing means 20 for analyzing a waveform signal output from 0 and detecting a predetermined effective sawtooth wave, and a measuring object according to a wavelength of each of the sawtooth waves detected by the signal processing means 20 Displacement data generating means 30 for generating displacement data of an object.

In addition, the signal processing means 20 detects the upper and lower envelopes of the sawtooth wave, and based on the upper and lower envelopes detected by the envelope detector 21, An intermediate line extracting unit 22 for extracting a substantially intermediate level of the intermediate line as an intermediate line, and an upper or lower area formed by the intermediate line extracted by the intermediate line extracting unit 22 and the sawtooth wave for each wave. Area calculation unit 23 to be calculated
And a sawtooth wave specifying unit 24 for specifying a wave having the area as an effective sawtooth wave when the area calculated by the area calculation unit 23 is larger than a predetermined area.

FIG. 4 is an explanatory diagram showing an example of calculating the area in the configuration shown in FIG. As shown in FIG. 4, the area calculation unit 23 vertically divides the saw-tooth wave k by an intermediate line obtained from the envelope h. Then, as shown in FIG. 4A, the area formed on the upper side by the sawtooth wave k and the intermediate line c is calculated. Alternatively, as shown in FIG.

Here, since the sawtooth wave is divided after obtaining the intermediate line c, even if the level of the sawtooth wave changes as a whole due to the fluctuation of the voltage level, the characteristics of the sawtooth wave are lost. Can accurately specify the saw-tooth wave without calculating the area by the area calculation unit 23 and comparing the calculated area with a predetermined constant area. , Which can be effectively removed.

When the fluctuation of the voltage level is small, the processing may be performed without performing division at the center line. In this case, the signal processing means 20 includes an envelope detector 21 for detecting one of the upper and lower envelopes of the sawtooth wave.
And an area calculator 23 for calculating an area formed by the envelope detected by the envelope detector 21 and the sawtooth wave for each wave.

When the envelope detecting unit 21 extracts the lower envelope h, the area formed below the sawtooth wave is calculated as shown in FIG. On the other hand, when the envelope detection unit 21 extracts the upper envelope, as shown in FIG. 5B, the area formed above the sawtooth wave is calculated.

Next, the operation of the displacement data generating means 30 will be described with reference to FIGS. As shown in FIG. 6, one of the sawtooth waves has a displacement λ /
Corresponds to 2. From the sawtooth wave shown in FIG. 6, it can be measured that the vibration plane displacement has occurred as shown. When the vibrating surface is displaced at high speed, the wavelength of the sawtooth wave is shortened, while when the wavelength is long, it is displaced slowly. In the example shown in FIG. 6, the wave number is counted based on the time when the sawtooth wave crosses the center line upward.

FIG. 7 is an explanatory diagram showing an example of a case where a fluctuation in voltage level and noise occur in a sawtooth wave. When the area calculator 23 shown in FIG. 3 calculates the area of the sawtooth wave shown in FIG. 7, the result is as shown in FIG. Since the noise part intersects the center line, when the wave number is counted by the method shown in FIG. 6, a number larger than the original wave number is counted.
As shown in (2), when the area is calculated and a waveform having an area smaller than a predetermined area is discarded, the inconvenience of counting the noise portion does not occur.

In the example shown in FIG. 7, when the area is less than a predetermined size (threshold), the wavelength is not treated as an intersection. Will be added to the wavelength.

The timing for calculating the area is when the sawtooth wave crosses the center line c from top to bottom or crosses from bottom to top. When calculating the area shown in FIG. 5, the area may be calculated at the peak of the sawtooth waveform. Further, the area may be calculated when the voltage exceeds the set voltage.

In the example shown in FIG. 7, the timing for treating the intersection is based on the middle line. As described above, the timing of plotting the vibration plane displacement from the sawtooth wave is the same as the calculation of the area, at the time of intersection with the intermediate line, at the time of the peak of the sawtooth wave, or when the voltage exceeds the set voltage.

Further, even when the area is calculated not in a portion divided by the intermediate line c but in a portion formed by the envelope h, the intersection between the intermediate line c and the sawtooth wave may be counted.

In this case, the envelope detector 21 has a function of detecting the upper and lower envelopes of the sawtooth wave. And
The envelope detecting unit 21 is provided with an intermediate line extracting unit 22 that extracts a substantially intermediate level of the envelope as an intermediate line based on the upper and lower envelopes detected by the envelope detecting unit 21. Further, when the effective sawtooth wave specified by the sawtooth wave specifying unit 24 crosses the center line extracted by the intermediate line extracting unit 22 upward or downward, the displacement data generating unit 30 A center line counting function for counting the waveform is provided.

As described above, in the present embodiment, the intermediate line c generated based on the envelope h is used for both the calculation of the area and the counting of the wave number. As a result, even if a change in the voltage level occurs, it is possible to perform processing in which this effect is effectively removed.

Further, in the example shown in FIG. 7, an example in which the vibration surface is displaced in one direction has been described. However, in the case where the direction of displacement is switched, the processing based on the area is similarly performed.
At this time, since the area where the direction switching occurs has a small area, the predetermined area may be changed based on the determination result by the separately provided direction switching time determination means. Furthermore, if the area is not the area of the division by the intermediate line but is a large area by the envelope, the difference in the area with the other parts hardly occurs even at the time of the direction switching, so that it depends on the relationship with the configuration of the direction switching time determination means. In some cases, it may be advantageous to remove noise based on the area of the envelope (see FIG. 12).

FIG. 8 is a block diagram showing the configuration of hardware resources according to the second embodiment.

As shown in FIG. 8, the vibration measuring device comprises a photodiode serving as a sensor head 41, and an amplifier 4 for amplifying a sawtooth wave detected by the photodiode 41.
2, an A / D converter 43 for converting the signal amplified by the amplifier 42 into digital data,
A memory 44 for storing digital data converted by the D converter 43 and a microcomputer 45 for counting the number of sawtooth waves which are digital data stored in the memory 44 are provided. Instead of this microcomputer 45, FP
The signal processing means 20 may be realized by a digital circuit such as a GA. FPGA is Field Programmable G
ATE Array is an integrated circuit that allows the user to freely rewrite the internal circuit configuration.

FIG. 9 is a flow chart showing an operation example of the vibration measuring device using the hardware resources shown in FIG.

First, the sawtooth wave is converted into digital data and stored in the memory 44 (step S21). The envelope of the sawtooth wave is identified from the waveform data in the memory 44 (step S22), and the intermediate voltage level is set as the center level for counting the number of waves (step S23).

Further, a sawtooth wave higher than the center level is extracted, and the area divided by the center level is calculated (step S24). A waveform having an area smaller than the predetermined area is not treated as a sawtooth wave. That is, the counting of the wave number by the waveform is invalidated (step S
24). Since the area of the noise is small, the wave number is not counted and erroneous measurement can be effectively prevented. Then, when the valid waveform crosses the center level, it is counted as a wave number (step S27). Further, when the waveform crosses the center level, the time is recorded and counted as a wave number (step S27).

As described above, according to the present embodiment, the center level is calculated from the envelope of the sawtooth wave, invalid waveforms are selected based on the area of the waveform divided by the center level, and when the effective waveform crosses the center level. Therefore, even if the voltage level of the sawtooth wave fluctuates or noise is superimposed on the signal, the wave number is not erroneously counted, and accurate displacement measurement can be performed.

[0048]

According to the present invention, according to the first aspect of the present invention, the area calculating step is performed on the area formed by the intermediate line and the input waveform signal. The part or the lower part is calculated, and the waveform specifying step specifies only a waveform having an area larger than a predetermined area as a valid waveform. Therefore, it is possible to provide an unprecedented superior waveform counting method capable of counting the number of generated waveforms by effectively removing the influence of fluctuations in voltage level and noise.

According to the second aspect of the present invention, since the saw-tooth wave specifying unit specifies a saw-tooth wave having a predetermined area or more as an object to be counted, the saw-tooth wave is effectively removed by removing the influence of voltage level fluctuation and noise. One of the waveforms can be specified, and the displacement data generating means can be measured based on the wavelength of the sawtooth waveform from which the influence of the noise specified by the sawtooth waveform identification unit has been removed. Since the displacement of the object is obtained, it is possible to provide an unprecedented excellent vibration measuring device that can accurately measure the displacement of the object without contact.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an example of an input signal whose wave number is to be counted according to the flowchart of FIG. 1;

FIG. 3 is a block diagram illustrating a configuration of a second exemplary embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an example of area calculation using an intermediate line, and FIG. 4 (A) is a diagram for calculating an upper area;
(B) is a figure which calculates the area of the lower side.

FIG. 5 is an explanatory diagram showing an example of area calculation using an envelope, and FIG. 5A is a diagram for calculating a lower area;
(B) is a figure which calculates the area of the upper side.

FIG. 6 is an explanatory diagram showing a relationship between an input waveform signal and displacement of a vibration surface.

FIG. 7 is an explanatory diagram showing an example of signal processing when an influence of a power supply level fluctuation and an influence of noise are added to an input waveform signal.

FIG. 8 is a block diagram showing a configuration of hardware resources of the vibration measuring device shown in FIG.

9 is a flowchart showing an operation in the configuration shown in FIG.

FIG. 10 is an explanatory diagram showing a schematic configuration of a vibration measuring device.

FIG. 11 is an explanatory diagram illustrating an example of a sawtooth wave affected by a change in voltage level.

FIG. 12 is an explanatory diagram illustrating an example of a sawtooth wave including a portion where the displacement direction of the vibration surface is switched.

[Explanation of symbols]

 Reference Signs List 10 light detecting means 20 signal processing means 21 envelope detecting section 22 intermediate line extracting section 23 area calculating section 24 sawtooth wave specifying section 30 displacement data generating means

Claims (4)

[Claims] 1. A measuring step of measuring a change amount of an input signal inputted from a measuring object via various media, and the number of times of intersection between a waveform measured in the measuring step and a predetermined reference value is represented by the waveform. In the waveform counting method comprising the step of counting the number of intersections according to the reception time of, before and after the step of counting the number of intersections after the measurement step, the upper and lower envelopes of the input signal measured in the measurement step An envelope detecting step of detecting, an intermediate line extracting step of extracting a substantially intermediate level of the envelope as an intermediate line based on the upper and lower envelopes detected by the envelope detecting step, and an extracting step of the intermediate line extracting step. An area calculating step of calculating, for each wave, an area formed for each wave on the upper or lower part of the intermediate line based on the obtained intermediate line and the input signal waveform measured in the measuring step; When the obtained area is larger than a predetermined area, a waveform specifying step of specifying one wave of the area as a valid waveform to be counted, wherein the number of intersections counting step is extracted by the intermediate line extracting step. A waveform counting method, wherein counting is performed when an intermediate line and a waveform specified in the waveform specifying step intersect in an upward direction or a downward direction with the intermediate line as a reference value. 2. A light detecting means for observing a laser beam reflected from an object to be measured, a signal processing means for analyzing a waveform signal output from the light detecting means and detecting a predetermined effective sawtooth wave, A displacement data generating means for generating displacement data of the object to be measured in accordance with a wavelength of each of the sawtooth waves detected by the signal processing means; An envelope detector for detecting upper and lower envelopes of the sawtooth wave, and an intermediate line extractor for extracting a substantially intermediate level of the envelope as an intermediate line based on the upper and lower envelopes detected by the envelope detector. An area calculating unit that calculates, for each wave, an upper or lower area formed by the intermediate line extracted by the intermediate line extracting unit and the sawtooth wave, and an area calculated by the area calculating unit. Vibration measurement apparatus comprising the sawtooth wave identification unit that identifies a wave having the area is larger than a predetermined area as an effective sawtooth wave. 3. A light detecting means for observing a laser beam reflected from an object to be measured, a signal processing means for analyzing a waveform signal outputted from the light detecting means and detecting a predetermined effective sawtooth wave. A displacement data generating means for generating displacement data of the object to be measured in accordance with a wavelength of each of the sawtooth waves detected by the signal processing means; An envelope detection unit that detects an envelope of the sawtooth wave, an area calculation unit that calculates an area formed by the envelope and the sawtooth wave detected by the envelope detection unit for each wave, A vibration measuring device comprising: a sawtooth wave specifying unit that specifies a wave having the area as an effective sawtooth wave when the area calculated by the area calculation unit is larger than a predetermined area. . 4. The envelope detection unit has a function of detecting upper and lower envelopes of the saw-tooth wave, and the envelope detector detects the upper and lower envelopes based on the upper and lower envelopes detected by the envelope detection unit. And an intermediate line extracting unit that extracts a substantially intermediate level of the envelope as an intermediate line, wherein the displacement data generating unit performs a saw-tooth wave specifying unit with respect to a center line extracted by the intermediate line extracting unit. 4. The vibration measuring apparatus according to claim 3, further comprising a center line counting function for counting a specified effective sawtooth wave when the wave crosses upward or downward.