JPH08234708A - Display accuracy inspection device for oscilloscope - Google Patents

Abstract

PURPOSE: To automatically inspect the display accuracy with respect to the horizontal or the vertical axis of an oscilloscope with an inexpensive configuration by inspecting the display accuracy of the oscilloscope based on the wave form of a calibration signal displayed on the display screen of the oscilloscope. CONSTITUTION: An oscilloscope 10 displays calibration signal to be supplied from a signal generator 12 to an input terminal. An optical guide plate 16 having an optical path is attached to the front of the display screen 14 of the oscilloscope 10. A photodetector 20 is provided with plural photodetecting elements, an analog/digital converter(ADC), etc. Each photodetecting element is attached to the exit of the optical path of the optical guide plate 16, detects passed light and supplies the analog output signal thereof to a multiplexer. The multiplexer selects either one of the analog signals according to an inputted select signal, converts it into a digital signal by the ADC and stores it in RAM. Then, a control section 28 calculates the display accuracy of the oscilloscope 10 from this digital value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscilloscope display accuracy inspection device for inspecting the display accuracy of an analog oscilloscope or a digital oscilloscope.

[0002]

2. Description of the Related Art When a vertical display accuracy or a horizontal display accuracy of an oscilloscope is inspected, a calibration rectangular wave signal whose value is known from a calibration signal generator is usually input to the oscilloscope. . When inspecting the vertical accuracy of the oscilloscope, for example, a rectangular wave signal having an amplitude value of 1 V is input to the oscilloscope, and the vertical axis of the oscilloscope is set to an appropriate range, for example, 200 mV / div (scale) and displayed. Using a cursor or the like on the screen, the amplitude value of the displayed waveform is read from the numerical display section, and the error percentage on the vertical axis is obtained from the error of this read value with respect to 1 div. When inspecting the horizontal accuracy of the oscilloscope, for example, a rectangular wave signal having a frequency of 1 MHz, that is, a period of 1 μs is input to the oscilloscope, and the horizontal axis of the oscilloscope is set to an appropriate range, for example, 1 μs / div and displayed. Use the cursor etc. on the screen to read the cycle of the displayed waveform from the numerical display and
The error percentage on the horizontal axis is calculated from the error with respect to div.
However, in this method, an operator must read and calculate a value from the tube surface of the oscilloscope, which causes a reading error and is troublesome.

Japanese Patent Publication No. 6-58594 describes a method for automatically confirming the display characteristics of an oscilloscope. In this method, a calibration signal is input to an oscilloscope, an image on the display screen is captured by a digital video camera, and the image is converted into a digital signal representing the brightness of each pixel of the pixel matrix of the display screen. A computer analyzes predetermined digital parameters representing the display characteristics of the display screen from the digital signal, and displays a graph representing these physical parameters. From the display image captured by the digital video camera, the amplitude and period of the display waveform can be obtained and compared with each value of the calibration signal to automatically measure the error percentage as described above. But,
Since this method uses a digital video camera, the apparatus is expensive, and an error occurs due to lens distortion.

Therefore, the object of the present invention is to
An object of the present invention is to provide an oscilloscope display accuracy inspection device capable of automatically inspecting the oscilloscope vertical or horizontal axis display accuracy with an inexpensive configuration without using a video camera or the like.

[0005]

SUMMARY OF THE INVENTION The present invention is an oscilloscope display accuracy inspection apparatus for inspecting oscilloscope display accuracy based on a waveform of a calibration signal displayed on an oscilloscope display screen. A signal generating means for generating a calibration signal controlled according to the above, and a plurality of optical paths each having an entrance arranged facing each other at a plurality of specific positions of the calibration signal displayed on the display screen of the oscilloscope are provided. Optical guide means, light detecting means for detecting light from the outlet of the optical path of the light guide, an analog-digital converter for converting an analog signal output from the light detecting means into a digital value, and the signal generating means. Means for supplying the control signal to the means, and storing the digital value from the analog-to-digital converter. Characterized in that it comprises a control means for determining a display quality.

The present invention is an oscilloscope display accuracy inspection device for inspecting the oscilloscope vertical axis display accuracy based on the waveform of a calibration signal displayed on the oscilloscope display screen. Signal generating means for generating the above-mentioned calibration signal whose amplitude can be adjusted, and two lights having entrances respectively arranged facing the position of the predetermined amplitude of the calibration signal displayed on the display screen of the oscilloscope. A light guide means provided with a passage, a light detection means for detecting light from the outlet of the light passage of the light guide, and an analog-digital converter for converting an analog signal output from the light detection means into a digital value. Changing the intensity of light from the display screen passing through the optical path when the control signal is supplied to the signal generating means and the amplitude of the calibration signal is changed. Depending storing the digital values from the analog-digital converter, and wherein the stored digital values 及上 Symbol predetermined amplitude that it comprises a control means for determining a vertical axis accuracy of the oscilloscope.

The present invention is a display accuracy inspection device for an oscilloscope which inspects the horizontal axis display accuracy of the oscilloscope based on the waveform of the calibration signal displayed on the display screen of the oscilloscope, and generates the calibration signal of a predetermined frequency. A signal generating means, a light guide means provided with a plurality of optical paths having entrances arranged at equal intervals along a horizontal line passing through substantially the center of the calibration signal displayed on the display screen of the oscilloscope, and the light guide means. A light detection unit that detects light from the exit of the optical path of the guide unit and generates a plurality of position detection signals that represent the horizontal position of the light; and a plurality of digital values for the plurality of position detection signals from the light detection unit. An analog / digital converter for converting into a digital image, and a plurality of the digital values from the analog / digital converter are stored, and the stored digital value and the display screen are stored. Wherein the a distance of a predetermined period of the calibration signal comprises a controller for determining a horizontal axis accuracy of the oscilloscope.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an accuracy inspection device for an oscilloscope according to the present invention. The oscilloscope 10 displays the calibration signal supplied from the signal generator 12 to the input terminal. In front of the display screen 14 of the oscilloscope 10, a light guide plate 16 is attached by an appropriate attachment means. As shown by the dotted line in FIG. 2, the light guide plate 16 has light passages 18 which are through holes having a diameter of about 0.3 mm at a plurality of specific positions to be described later. The width of the trace or line of the oscilloscope 10 is several times this diameter of the light path 18. The light guide plate 16 is made of a material such as aluminum which is easy to form a through hole and is inexpensive. When a part of the waveform is displayed at a position on the display screen 14 facing the optical path 18,
The light of the bright line passes through the optical path 18. The light passage 18 preferably has a black inner surface in order to allow light from the portion of the display screen directly in front of the entrance to pass therethrough and to attenuate light from other portions well within the light passage 18.

The photodetector 20 includes a plurality of photodetector elements 22,
Multiplexer 24 and analog / digital converter (A
DC) 26. Each light detecting element 22 is a light guide plate 1.
6 is attached to the exit of the optical path 18 and detects the light passing through the optical path 18 and supplies its analog output signal to the multiplexer 22. The multiplexer 22 selects any one analog output signal of the photodetector element 22 according to the input selection signal and supplies it to the ADC 26. ADC2
6 converts the input analog signal into a digital signal.

The controller 28 has a microprocessor, a random access memory (RAM), and a read only memory (ROM) that stores a program for performing a desired operation described later. The controller 28 is the ADC 2
6 receives the digital output signal of No. 6 and stores it in the RAM, supplies the input selection signal to the photodetector 20, and outputs a signal setting signal for setting the frequency and amplitude of the output signal of the signal generator 12. 12 and data communication with the computer 30. Computer 30
Is connected to a display 32 such as a CRT or a liquid crystal display.

FIG. 3 is a plan view showing the positional relationship among the scale lines of the display screen 14, the plurality of optical paths 18 provided in the light guide plate 16, and the photo-detecting elements 22 attached thereto. The optical path 18 is a pair of vertical axis accuracy inspection optical paths 1.
Optical path 1 for 8v1, 18v2 and many horizontal axis accuracy inspections
It consists of 8h1-18hN. Light path 18v1 and 18v2
Is a vertical position for displaying the maximum and minimum amplitude parts of the calibration signal on the display screen 14, for example, +2.5 div and -2.5 div, respectively, at a distance of about +1 div and -1 div from the central vertical scale line. And formed. The light passages 18h1 to 18hN are formed at positions slightly apart from the center horizontal scale line and are formed at equal intervals along the line.
Note that this spacing is, for example, 0.5 mm, which is smaller than the width of the bright line. However, in the drawing, this space is shown large for the sake of illustration. In order not to block the light of the bright line, it is desirable that the optical path does not overlap the scale line. Light path to light path 18v1 and 18
Corresponding to v2, photodetection elements 22v1 and 22v2, which are ordinary photodiodes, are attached. Further, in a known positional relationship with respect to the optical paths 18h1 to 18hN, 1
An elongated light detecting element 22h, which is a dimensional position detecting photodiode, is attached so as to cover these light paths. This one-dimensional position detection photodiode is capable of detecting the position in the lengthwise direction irradiated with light, and there is a model name S5730 sold by Hamamatsu Photonics KK or the like.

Next, the oscilloscope 1 according to the present invention is used.
The operation of the accuracy check of 0 will be described. FIG. 4 is a diagram for explaining the vertical axis accuracy inspection according to the present invention. When the operator uses the keyboard of the computer 30 or the input means such as the menu on the display 32 to input a command for performing the vertical axis accuracy inspection, the controller 28 sends a corresponding instruction signal from the computer 30. Received, as a calibration signal for vertical accuracy inspection, amplitude ± 2.5V, frequency 1kHz
The signal generator 12 is controlled so as to output the rectangular wave signal. Further, the display 32 displays an instruction to the operator to set the oscilloscope 10 to the vertical axis of 1 V / div and the horizontal axis of 0.2 ms. If the oscilloscope 14 can be digitally controlled, the oscilloscope 10 may be automatically set via the controller 28 according to an instruction from the computer 30.

First, the controller 28 controls the multiplexer 24 to select the output signal of the photodetection element 22v1 by the selection signal. At this time, if the photodetection element 22v1 is detecting the light of the bright line, that is, the controller 28 adjusts the calibration signal so that the optical path 18v1 does not overlap the bright line of the displayed waveform. Next, the controller 28 continuously increases or decreases the positive output voltage of the signal generator 12 by, for example, 0.02 V, and when the output signal is obtained from the photodetector element 22v1, the controller 28 outputs the signal from the ADC 26. The corresponding digital value is stored in RAM. Further, the controller 28 sequentially changes the positive output amplitude of the signal generator 12 in the same direction, and stores the output digital value of the ADC 26 for each output voltage in the RAM.

When the amplitude of the output signal from the photodetector element 22v1 disappears to 0, the controller 28 stops the storage in the RAM. Next, the controller 28 searches for the maximum value of the accumulated values and obtains the output amplitude of the signal generator 12 when the maximum value is reached. When a plurality of the same maximum values exist in succession, the positive output amplitude of the signal generator 12 corresponding to the maximum value in the middle is obtained. Thereby, the first output voltage of the signal generator 12 when the center of the bright line of the maximum amplitude of the display waveform overlaps the optical path 18v1 is obtained.

Next, the controller 28 responds to the input selection signal by
The multiplexer 24 controls to select the photodetector element 22v2. Except for changing the negative output voltage of the signal generator, the procedure is similar to that for the photodetector element 22v2, and the center of the bright line of the minimum amplitude of the display waveform is the optical path 18v.
Obtain the second output voltage of the signal generator 12 when it overlaps with 2. The first and second output voltages of the signal generator 12 are, for example,
Given that they are + 2.56V and -2.54, respectively, the amplitude of the calibration signal is 2.56V-(-2.54V) = 5.1V. Since this amplitude is displayed on the display screen 14 with a smaller amplitude of 5V, the vertical axis error percentage Ev of the oscilloscope 10 is Ev = (5.0V-5.10V) /
5V × 100% = − 2%.

FIG. 5 is a diagram for explaining the horizontal accuracy inspection according to the present invention. When the operator uses the input means of the computer 30 to input that the horizontal axis precision inspection is to be performed, the controller 28 receives an instruction signal corresponding to the instruction from the computer 30, and uses the amplitude as a calibration signal for the horizontal axis precision inspection. The signal generator 12 is controlled so as to output a rectangular wave signal of ± 2.5 V and a frequency of 10 kHz. Further, the display 32 displays the oscilloscope 14 on the vertical axis of 1 V / div,
Display an instruction to the operator to set 100 μs / div on the horizontal axis. According to this setting, a rectangular signal waveform for 10 cycles is displayed on the display screen 14 having a horizontal axis scale of 10 div.

The controller 28 controls the multiplexer 24 to select the output signal of the photo-detecting element 22h according to the selection signal. The photodetector element 22h, which is a one-dimensional position detection photodiode, detects light from a plurality of light paths that overlap the vertical bright line of the display waveform and that allows the light to pass therethrough among the light paths 18h1 to 18hN, and position detection signals corresponding thereto are detected. Is output. The photodetector 22h is used by the oscilloscope 10
These position detection signals are sequentially output during one sweep period. In the illustrated example, output signals of 20 position detection detection signals are generated from the display waveform for 10 cycles. The position detection signal is
It is converted into a digital value by the ADC 26, supplied to the controller 28, and stored in the RAM. The controller 28 obtains values representing 20 light detection positions from the accumulated digital values. Next, from these values, for example, any 16 consecutive values corresponding to 8 cycles of the calibration signal are selected, and the difference between the maximum value and the minimum value thereof is obtained. For example, this value is 7.9
Corresponding to div, the horizontal axis error percentage Eh of this oscilloscope 10 is Eh = (7.9div-8.0div) /
8div x 100% = -1.25%.

Although one embodiment of the present invention has been described above, it will be apparent to those skilled in the art that various modifications can be made. The photodetector in the horizontal direction is one such as the photodetector 22h.
A plurality of shorter photodetectors than one elongated one may be arranged at positions corresponding to the vertical emission lines of the display waveform of the calibration signal. Since it is only necessary to process the output signal of one photodetector for one or more sweep periods of this oscilloscope, it is possible to use a high frequency horizontal calibration signal.

[0019]

According to the display accuracy inspection apparatus for an oscilloscope of the present invention, an optical path is provided at a position corresponding to the amplitude or frequency of the display waveform of the calibration signal in front of the display screen of the oscilloscope on which the calibration signal is displayed. Arrange the light guide means,
Since the display accuracy can be inspected based on the light that passes through this,
The display accuracy of the vertical axis or horizontal axis of the oscilloscope can be automatically inspected with an inexpensive configuration without using a digital video camera or the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a display accuracy inspection device for an oscilloscope according to the present invention.

FIG. 2 is a block diagram showing a configuration inside the photodetector of FIG.

FIG. 3 is a diagram showing a positional relationship between a scale line, an optical path, and a photodetector element on a display screen of an oscilloscope.

FIG. 4 is a diagram for explaining vertical axis display accuracy inspection by the apparatus of the present invention.

FIG. 5 is a diagram for explaining a horizontal axis display accuracy inspection by the device of the present invention.

[Explanation of symbols]

 10 Oscilloscope 12 Signal Generator 14 Display Screen 16 Optical Guide Means 18 Optical Path 22 Optical Detection Means 26 ADC 28 Controller

Claims (3)

[Claims] 1. An oscilloscope display accuracy inspection device for inspecting oscilloscope display accuracy based on a waveform of a calibration signal displayed on an oscilloscope display screen, the signal being controlled by a control signal to generate the calibration signal. Generating means, light guide means provided with a plurality of optical paths each having an entrance arranged facing each other at a plurality of specific positions of the calibration signal displayed on the display screen of the oscilloscope; Photodetection means for detecting the light from the exit of the optical path, an analog-digital converter for converting the output analog signal of the photodetection means into a digital value, and the control signal supplied to the signal generation means, Control means for storing the digital value from the analog-digital converter and obtaining the display accuracy of the oscilloscope from the digital value; Display accuracy inspection apparatus oscilloscope, characterized in that it comprises. 2. An oscilloscope display accuracy inspection apparatus for inspecting vertical axis display accuracy of an oscilloscope based on a waveform of a calibration signal displayed on an oscilloscope display screen, the amplitude being set to a predetermined amplitude according to a control signal. And an optical signal generating means for generating the calibration signal, which is adjustable, and two optical paths each having an entrance arranged to face the position of the predetermined amplitude of the calibration signal displayed on the display screen of the oscilloscope. The light guide means, a light detecting means for detecting light from the outlet of the light path of the light guide, an analog-digital converter for converting an analog signal output from the light detecting means into a digital value, and the signal The control signal is supplied to the generating means, and in response to a change in the intensity of light from the display screen passing through the optical path when the amplitude of the calibration signal is changed. And storing said digital values from the analog-digital converter, the stored display accuracy inspection apparatus oscilloscope, characterized in that it comprises a digital value 及上 Symbol predetermined amplitude and control means for determining the vertical axis accuracy of the oscilloscope. 3. An oscilloscope display accuracy inspection device for inspecting the horizontal axis display accuracy of the oscilloscope based on the waveform of the calibration signal displayed on the display screen of the oscilloscope, the signal generation generating the calibration signal of a predetermined frequency. Means, a plurality of light guide means having a plurality of light paths having entrances arranged at equal intervals along a horizontal line passing through substantially the center of the calibration signal displayed on the display screen of the oscilloscope, and the light guide means. Detects the light from the exit of the above optical path of
A photodetector that generates a plurality of position detection signals that represent the horizontal position of the light, an analog-digital converter that converts the plurality of position detection signals from the photodetector into a digital value, and an analog-digital converter. A controller for storing a plurality of the digital values from the instrument and determining the horizontal axis precision of the oscilloscope from the stored digital values and the distance of the predetermined period of the calibration signal on the display screen. Display system inspection device for oscilloscope.