JPS63205571A - Crest value measuring instrument - Google Patents

Abstract

PURPOSE:To measure a crest value with high accuracy by calculating the maximum measured crest value in the display period of a signal to be measured from the display crest value of a reference signal based upon image data, the ratio of the maximum crest value of the signal to be measured, and the reference value of the reference signal. CONSTITUTION:An audio intermediate-frequency signal inputted to an input terminal 1 for the signal to be measured is inputted to a reference signal inserting circuit 2. A signal in the measurement period which is outputted by the circuit 2 and a 3rd gate signal are inputted to the vertical input terminal IN and external trigger terminal EXT of an oscilloscope 3 respectively. The display image on this oscilloscope 3 is picked up by an image pickup device 4, so image data on the display screen is outputted from the device 4 to an image processing part 6. Then when image data of one image plane is inputted to a processing part 6, the processing part 6 calculates the number A of picture elements of the crest value of the reference value and the number B of picture elements of the maximum crest value in the display period, and outputs them to a data processing part 7. Further, the processing part 7 calculates the maximum measured crest value in the display period according to the numbers A and B of picture elements and the reference value of the reference signal.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is used, for example, to inspect and adjust the output level of each circuit of a television receiver or video tape recorder. The present invention relates to a peak value measuring device that automatically measures the peak value of an analog waveform having characteristics.

[Conventional technology]

Conventionally, the input and output levels of each circuit of a television receiver or video tape recorder have been inspected and adjusted using, for example, the maximum or one-cycle wave of an audio, video intermediate frequency signal, or a color signal modulated with a subcarrier. This is done by measuring the high value.

By the way, the measurement of the maximum value or the peak value of each period of a signal under measurement of an analog waveform having periodicity such as a modulated wave signal such as an audio or video intermediate frequency signal is usually performed by one of the following methods.
10, (au>, aψ).

A method in which the measurer reads the waveform of the signal being measured as it is displayed as a sweep on an oscilloscope.

(11) A method in which the peak level of the signal under test is held, a voltage signal at the hold level is supplied to a voltmeter, and the measurer reads the displayed value of the voltmeter.

((ii) A method of converting the signal under test into digital data and processing the digital data using a microcomputer or the like.

A method of sweeping and displaying a signal under test on a digital storage oscilloscope with Qφ digital memory.

In the middle, (i+) is not effective unless the measurer processes the read value and measures the peak value, but (liI),
IIV), the peak value is automatically measured.

In addition, Special Publication No. 58-6426 (HO4N 5/1
3) describes that a preset black and white vertical striped image is displayed on a television screen, the screen is read by a line scan camera, and the output data of the camera is processed to measure the image amplitude. has been done.

[Problem that the invention seeks to solve]

By the way, in the above-mentioned method, the reading error of the measurer and the sensitivity calibration error of the oscilloscope have a large influence on the measurement, and in the method (11), the reading error of the measurer, the peak hold circuit, the voltage converter, etc. The setting gain error has a large effect on the measurement.

In addition, in the above-mentioned (itD method), setting gain errors of voltage converters, analog/digital converters, etc. have a large influence on measurement, and the specific signal under measurement corresponding to a processing program preset in a microcomputer etc. There is a disadvantage that only measurements can be performed.

Furthermore, the +1 method has the disadvantage that the sensitivity calibration error of the oscilloscope has a large effect on the measurement and the equipment becomes very expensive.

On the other hand, in the case of the apparatus described in the above-mentioned publication, the accuracy of the image pattern displayed on the television screen, that is, the black and white vertical striped pattern, has a great influence on the measurement, and there are disadvantages in that only the image amplitude can be measured.

In other words, the conventional peak value measurement device used to measure the peak value of the signal under test of this kind of analog waveform with periodicity suffers from one of the following errors: reading error, oscilloscope sensitivity calibration error, and setting gain error 1. There is a problem in that accurate measurements cannot be made unless one or more of them are strictly controlled.

In addition, (ii), the method of (iψ) and the method of the publication have problems such as expensive equipment or lack of periodicity.

[Failure to solve the problem]

This invention was made with the above points in mind,
A peak value measuring device that measures the peak value of a signal under test having an analog waveform with periodicity, such as a modulated wave signal, includes a DC generator that generates a DC signal with a set reference value, and a DC signal that is synchronized with the signal under test. periodic pulse signal.

a gate signal generation circuit that includes a counter that counts for a set number of cycles and sets a display period, and that processes an output signal of the counter to generate a gate signal for replacement and insertion of the DC signal; a signal gate circuit that replaces the part of the measured signal set by the replacement/insertion gate signal within a period with the DC signal and outputs the same; a sweep display device that displays a signal and a waveform of the DC signal in an l sweep; a solid-state imaging device that captures an image of the display screen of the display device and outputs image data; and the reference obtained by processing the image data. Based on the ratio of the displayed peak value of the signal to the maximum or each one cycle of the signal under test, and the reference value, the measured peak value of the signal under test at the maximum or each one cycle within the display period. This is a peak value measuring device characterized by comprising a calculation processing device that calculates the peak value.

[Effect]

Therefore, the measured signal in the display period is partially replaced with a DC signal and displayed on the display device in one sweep, and
The display screen of the display device is imaged by a solid-state imaging device,
and the maximum display peak value of the reference signal based on the image data output from the solid-state imaging device and the maximum value of the signal under test, or 1 for each.
The maximum measured peak value within the display period of the signal under test or each cycle is calculated based on the ratio of the peak values of the period and the reference value of the reference signal, so just by stabilizing the reference signal, The peak values of various signals under test can be measured with high precision.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings of FIGS. 1 to 7 showing one embodiment thereof.

Figure 1 shows the case where the application is applied to the peak value measurement of the audio intermediate frequency signal (hereinafter referred to as SIF signal) of a television receiver. In the figure, (1) is the signal input terminal to be measured into which the 8IF signal is input. , +21 is a reference signal insertion circuit connected to input terminal +11, +31 is a single-phenomenon oscilloscope forming a sweep display device, and vertical input terminal (IN).
A signal of the measurement period, which will be described later, output from the insertion circuit (2) is input to the input circuit (2), and a third gate signal, which will be described later, output from the insertion circuit (2+), is input to the external trigger terminal (FAT).

[4] is a solid-state imaging device consisting of a COD camera with a 525 x 525 pixel array, which captures an image of the display screen of the oscilloscope (3) and outputs binary image data indicating the brightness and darkness of each pixel.

(5) is an arithmetic processing unit connected to the imaging device +41, which is composed of an image processing unit (6) and a data processing unit (7), and processes the image data of the imaging device +4) to generate a measurement wave of the 81F signal. Calculate the high price.

By the way, the insertion circuit 2) is configured as shown in Fig. 2, and in the same figure, C81 is an input buffer circuit f9).
, 1st to 8th multiples ff'IO, QD, C
This is a signal gate circuit consisting of 2 and an output buffer circuit a3, and the 81F signal is input to the buffer circuit (9), and the output signal of the buffer circuit (to) is output to the input terminal (IN) of the oscilloscope (3). do.

(141 is a DC generator made of a stabilized DC power supply or the like, which generates a DC signal with a voltage of a preset reference value and outputs it to the multiplexer α.

al19 is a waveform shaping circuit that outputs a periodic pulse signal synchronized with the 81F signal. α· is a counter αη and the first to eighth gate signal generating circuits o8. α wound.

This is a gate signal generation circuit consisting of a wire.A periodic pulse signal is input to the counter ση, and based on the output signal of the counter αη, a signal is sent from the generation circuit (18)-4 to the multiplexer 0O-(2) for setting the display period. The first gate signal Ga for replacement insertion, the second gate signal Ga for replacement insertion. Third gate signal Gb
, Gc, and also outputs the third gate signal Gc for the generating circuit to the external trigger terminal (EXT) of the oscilloscope (3).

Note that the gain of the buffer circuits (91, ('13) is set to 1.

Further, the peak value of the reference signal, that is, the reference value, is set to 1 (V).

Then, the display period is set to 3 periods of the signal of the input terminal (1), the first period of the display period is set as the replacement insertion period of the DC signal, and the remaining 2 periods of the display period are 81
When measuring the maximum peak value of the F signal, each section in FIGS. 1 and 2 operates as described below.

First, the 8IF signal of the input terminal 11) shown in FIG. A periodic pulse signal with a period of one phase is input.

Note that the signal input to the shaping circuit α9 is, for example, SI
It consists of an oscillation output signal from an oscillator that is PLL-controlled by the F signal, and changes as shown in FIG. 8(b).

In addition, the shaping circuit port O shapes the input signal into a square wave, and the third
A periodic pulse signal shown in Figure (e) is output.

Then, for example, by operating a switch, the counter 0'i
) is activated, the counter αη converts the periodic pulse signal into 3
It counts during the period, sets the display period of the three periods, and outputs an output signal consisting of the count data to the generation circuits (to) to kan.

Furthermore, the generation circuits 010 to 010 (1) are composed of, for example, a combination circuit of a logic gate and a flip-flop, and process the output signal of the counter αη to generate the first to eighth gate signals G.
generate a-Gc, respectively.

That is, the generation circuit a8 generates the first gate signal G that becomes high level when three cycles of the display period have elapsed from the rising edge to of the first periodic pulse signal immediately after the counter αη is activated.
a, and the generating circuit α9. The pen is shown in Figure 3(d),
As shown in (e), the second periodic pulse signal is at a high level for only one period and a half period from the rising edge of the first periodic pulse signal. Third gate signal Gb.

Generates Gc.

And the multiplexer (10, Qυ is the gate signal G
The multiplexer 02 selects and outputs the output signal of the multiplexer 011 during the high level of the gate signal Gc by turning it off and setting the output level to the ground level (0 (V)) during the high level of the gate signal Gc. At the same time, while the gate signal Gc is at a high level, the DC signal of the generator α4 shown in FIG. 8 is selected and output.

Therefore, from multiplexer aO to multiplexer 0
11, the SIF signal until the end of the display period is output, and the multiplexer a
2, an 81F signal is output with only the first period of the display period fixed at the ground level.

Then, the multiplexer (6) selects the DC signal in the first half of the first period of the display period, and selects the 8IF signal in the remaining two periods of the display period, so that the buffer circuit α3 selects the DC signal in the first half of the first period of the display period, and the 8IF signal is selected in the remaining two periods of the display period. As shown in FIG. 2, a signal obtained by replacing and inserting the reference signal is output in the first half of the first cycle of the display period from to.

Furthermore, the output signal of the buffer circuit αJ is input to the input terminal (IN
), and the third gate signal Gc is input to the external input terminal (FIXT), so the oscilloscope +3
) sweeps and displays the signal at the input terminal (IN) using the eighth gate signal as an external trigger signal, and at this time, the waveform of the display period shown in FIG. 4 is displayed on the oscilloscope +31 in l sweep.

Also, the display screen of the oscilloscope (3) is
), the processing unit (
6), image data of 525 x 525 pixels on the display screen of FIG. 4 is output.

The processing units (6) and (7) are both composed of microcomputers, and when one screen worth of image data shown in FIG. 5 is input to the processing unit (6), the processing unit (61) Based on the image data, the number of pixels A and B (bits) of the displayed peak value of the reference signal in FIG. The number B [bits] is calculated and the processing unit (7
).

Furthermore, the processing unit (7) inputs the input pixel numbers A and B,
Based on the reference value of the reference signal set in advance, the measured value corresponding to the number of pixels B, that is, the maximum measured peak value B within the display period is calculated as described below.

Now, the reference value is a (V:], and the measured peak value is x (V
) means to calculate X by processing the formula x = ”H,
The obtained X is output as the measured peak value B.

Then, when A = 150 C bits] and B = 240 [hits], a = l(V), so X = 1
- The voltage is 1.6 (V), and data of 1.6 (Vl) is output from the processing unit (7) as the measured peak value B'.

By the way, when the thickness of the bright line of the oscilloscope (41) becomes larger than one pixel of the imaging device (41), the processing unit (6)
When calculating A and B, as shown in Figure 6,
A using the center O pixel of the bright line (L).

B is required.

In addition, l! in Figure 6! a and gb indicate the outside and inside of the bright line, and the length of /a to lO and the length of l to 10 are 1/2 of the thickness L of the bright line.

Therefore, in the case of the above embodiment, based on the ratio of the displayed peak value of the SIF signal obtained from the image data of the imaging device (41) and the peak value of the reference signal, and the reference value, the maximum The wave height value of is automatically measured, and at this time, the sensitivity calibration error of the oscilloscope (3) etc.
Since the signal and the reference signal are affected equally, the measurement accuracy depends almost only on the accuracy of the reference value.

The use of a commercially available relatively stable and highly accurate regulated DC power supply for the generator α4 is extremely effective compared to, for example, methods that strictly control sensitivity calibration errors of the oscilloscope (3). Easy and accurate measurements
For example, highly accurate inspection and adjustment of the input and output levels of the audio intermediate frequency amplification circuit of a television receiver can be easily performed.

Furthermore, a general-purpose, inexpensive oscilloscope (31, etc.) can be used, and the apparatus can be formed at a low cost.

Furthermore, even when a signal with this kind of analog waveform, such as a modulated wave signal other than an SIF signal, is used as the signal to be measured, it is only necessary to change the signal at input terminal +11, and a highly versatile device can be provided. .

In the embodiment described above, the display period was set to three cycles, and the DC signal was replaced and inserted in the first half of the first cycle, but the display period and the replacement insertion position of the DC signal for one period were different from those in the embodiment. Of course, it is also good.

Furthermore, in the above embodiment, the explanation was given on the assumption that the peak values of the two periods within the display period are equal, but if the peak values of the two periods are not equal, the processing unit (6) changes the peak value of the larger period. Of course, it is calculated.

Furthermore, it is also possible to measure the peak value of each cycle of the signal under measurement within the display period, and in this case, the processing unit (6) may calculate the display peak value of each cycle of the signal under measurement.

〔Effect of the invention〕

As described above, according to the peak value measuring device of the present invention, the signal to be measured during the display period is partially replaced with a DC signal and displayed on the sweep display device in one sweep, and the signal on the display device is The screen is imaged by a solid-state imaging device, and the ratio of the displayed peak value of the reference signal based on the image data output from the solid-state imaging device and the peak value of the maximum or each period of the signal under measurement, and the reference value of the reference signal. As a result, the peak value measured during the display period of the signal under test or for each period is calculated, so it is possible to accurately measure the peak value of various signals under test simply by stabilizing the reference signal. It is possible to accurately measure the peak values of various signals under test at low cost and easily.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1 to 6 show one embodiment of the peak value measuring device of the present invention, in which FIG. 1 is a block diagram, FIG. 2 is a partial detailed block diagram, and FIG. Figures (a) to (g) are timing charts for explaining the operation, Figure 4 is a waveform diagram of the display screen, and Figures 5 and 6 are diagrams for explaining processing of image data. (1)...Measurement signal input terminal, (21...Reference signal insertion circuit, 13+...Oscilloscope, (4)...
・Solid-state imaging device, +5)...Arithmetic processing unit, (81・
...Signal gate circuit, α4...DC generator, αQ...
・Gate signal generation circuit.

Claims (1)

[Claims] (1) A peak value measuring device that measures the peak value of a measured signal having an analog waveform with periodicity, such as a modulated wave signal, comprising: a DC generator that generates a DC signal with a set reference value; and the measured signal. It has a counter that sets a display period by counting a periodic pulse signal synchronized with the signal for a set number of cycles, and processes the output signal of the counter to create a gate signal for replacing and inserting the DC signal. a signal gate circuit that replaces a portion of the signal under test set by the replacement insertion gate signal within the display period with the DC signal and outputs the DC signal; a sweep display device that displays the waveforms of the output signal under measurement and the DC signal during the display period in one sweep; a solid-state imaging device that captures an image of the display screen of the display device and outputs image data; and the image. Based on the ratio of the displayed peak value of the reference signal obtained by processing data to the maximum or each period of the displayed peak value of the signal under test, and the reference value, within the display period of the signal under test. 1. A wave height measuring device comprising: an arithmetic processing device that calculates a maximum measured wave height value or a measured wave height value for each cycle.