JPH07128371A - Digital oscilloscope - Google Patents

Abstract

PURPOSE:To make it possible to express frequency with dot density while preventing aliasing through composition of an actual sample display and a P-P compression display. CONSTITUTION:A display data generating means 6 stores an actual sample data from an acquisition memory 4 into a display memory 7, composes an actual sample display and a P-P compression display, and delivers a digital composite display signal. When a data is stored in the memory 4 and one acquisition is ended, an operation for indicating the content stored in the memory 4 is started. The stored data is read out by such number as necessary for one raster display at a time in synchronism with a raster period signal (a). It is then fed to a P-P detector 5 and outputted as a P-P data (d) while simultaneously an acquisition data is stored in the memory 7. Means 6 combines the contents of a stored data (c) and the data (d) and then delivers the combined data. Upon finishing the operation for all data of one acquisition, a composite waveform for one screen is displayed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved digital oscilloscope for preventing aliasing in the digital oscilloscope.

[0002]

2. Description of the Related Art When a waveform is displayed, a digital oscilloscope samples an analog input signal at regular time intervals, converts it into a digital signal, and displays it on the screen as a waveform based on the digital value to observe the input signal. It is a thing.
In such a digital oscilloscope, when the cycle of the input signal is close to the sampling frequency (so-called the frequency of the so-called sampling signal is close to the Nyquist frequency), as shown in FIG. The waveform of the input signal cannot be displayed and aliasing occurs.
For example, in an analog oscilloscope, aliasing does not occur because sampling is not performed, and information about the frequency of the waveform is displayed as brightness on the screen. I can't.

Conventionally, in order to prevent the occurrence of such aliasing, the sampling period is set sufficiently higher than the period of the input signal even if the time axis resolution on the screen display is low. For example, in displaying one raster, a method of performing waveform display such as PP compression display (FIG. 7) or dot display of all data (FIG. 8) based on a plurality of data has been used. The raster here corresponds to the resolution in the time axis direction (horizontal axis of the screen). A simple illustration is shown in FIG.

However, in the P-P compression display, the maximum value and the minimum value (acquisition data shown by ● in FIG. 6) are detected from the data sampled as one raster, and the data in between are detected as shown in FIG. Raster interpolation is performed (in addition to the interpolation data indicated by ◯ in FIG. 6) for display. Therefore, although the aliasing itself is eliminated, in some cases, as shown in FIG. 7, all the waveforms are filled, and the input signal is erroneously observed.

A dot display of all data sampled for one raster (hereinafter referred to as "actual sample display")
Since it is expressed by dots as shown in FIG. 8, it is visually observed that aliasing occurs.

[0006]

Therefore, the digital oscilloscope has a problem that there is no efficient method for solving the occurrence of aliasing. In addition, there is a problem in that it is difficult to understand the frequency of a certain value in the input signal in the above two types of display methods. The present invention solves such a problem and provides a digital oscilloscope that efficiently solves the occurrence of aliasing.

[0007]

According to the present invention, an input signal storage means for storing a series of data groups in which an analog input signal is digitized, and one raster display of the data stored in the input signal storage means are displayed. The maximum and minimum value detecting means for detecting the maximum value and the minimum value of the read data, and the maximum and minimum values from the maximum and minimum value detecting means. And interpolating means for interpolating data between the interpolating data and the displaying means for synthesizing and displaying the interpolating data from the interpolating means and the data from the input signal storing means. It is a digital oscilloscope characterized in that it can observe stored data at the same time.

[0008]

In the digital oscilloscope according to the present invention,
Since the real sample display and the PP compressed display are combined, the occurrence of aliasing can be efficiently prevented and the frequency of the waveform can be understood by the dot density.

[0009]

1 is a block diagram showing a hardware configuration for implementing an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a front end, which is made up of an attenuator, an amplifier, a filter, a trigger comparator, and the like, and which inputs a signal to be measured from outside the digital oscilloscope and triggers when the input signal has a certain condition. It is a part for outputting a signal. An AD converter 2 digitally converts the output from the front end 1.

Reference numeral 3 is an acquisition controller, 4 is an acquisition memory, and the trigger signal output from the front end 1 and the microprocessor (hereinafter referred to as "CP").
Based on the control signal from the U) 11), an operation for storing the digitally converted data out of the digital data output from the AD converter 2 at the timing related to the trigger signal in the acquisition memory 4 is performed. To do.

Reference numeral 5 denotes a maximum / minimum value detecting means (hereinafter referred to as "P-P detector"), which stores 1 data required for displaying one raster.
The data is read at the timing necessary for displaying the raster, and the maximum value and the minimum value of the data necessary for displaying the one raster are detected.

Reference numeral 6 is a display data generating means, and 7 is a display memory. The operation is to interpolate the data between the maximum value and the minimum value output from the PP detector 5, and the actual sample data from the acquisition memory 4. Operation of storing in the display memory 7,
Further, the display data generating means 6 performs an operation of synthesizing the actual sample display and the PP compressed display and outputting the synthesized display signal as a digital value. Further, the display memory 7 is realized by a rewritable VRAM.

Reference numeral 8 denotes a DA converter for converting the composite display signal of the digital value from the display data generating means 6 into an analog signal. 9
Is a display means for displaying by an analog signal from the DA converter 8. For example, raster scan type C
Realize with RT etc.

A display controller 10 outputs a synchronizing signal for display to the acquisition controller 3, the PP detector 5, the display data generating means 6 and the display means 9. The CPU 11 described above outputs a control signal to the front end 1, the acquisition controller 3, and the display data generating means 6.

The operation of such a configuration will be described, but the operation of the acquisition will be described on the premise. For example,
The number of input signals that can be sampled with one trigger signal generation is 10,000. The data of 10,000 points is called acquisition data and is stored in the acquisition memory 4 described above. Also assume that there are 500 rasters on the display screen, and raster scan (for the screen,
It is assumed that the screen is swept vertically.

Under this condition, the number of acquisition data that can be used to display one raster is two.
It is 0. If the trigger point is the left end of the tube surface, 1 acquisition is completed by sampling 10,000 data after the trigger is generated and storing the data in the acquisition memory 4.

The operation of the configuration of the present invention will be described below with reference to the time chart of FIG. In FIG. 2, (a) is a raster synchronization signal output from the display controller 10. (b) shows the fluctuation of the acquisition data read from the acquisition memory 4 via the acquisition controller 3. (c) is stored data and shows what kind of data is stored in the display memory 7.

(D) is PP data, which is the acquisition data (b) for each raster read from the PP detector 5.
Of these, the maximum and minimum values are data. (e) is display data which is read from the display data generating means 6. Based on this display data (e), the composite waveform is displayed on the display means 9.

When 10000 points of data are stored in the acquisition memory 4 after the trigger signal is generated (when one acquisition is completed), the raster scan timing is determined by this raster synchronization signal (a). The operation of displaying the contents stored in the acquisition memory 4 starts.

As shown in (b), the data stored in the acquisition memory 4 is synchronized with the raster sync signal (a), and the number of data (20 points) required for displaying one raster Read out. These 20 points of data are
It is input to the PP detector 5, and is output as (d) PP data. At the same time, the acquisition data itself is also stored in the display memory 7 via the display data generating means.

The display data generating means 6 stores the stored data (c)
And the contents of PP data (d) are combined and output. There are various methods for this synthesis, but PP data
(d) and PP compressed display data using interpolation data,
Different luminance display information or different color information is given to the stored data (c), and they are displayed in an overlapping manner as shown in FIG. Specifically, it is converted to display data and whether the corresponding pixel is due to PP compression display or stored data (c)
Different bit data depending on the cause. By converting this bit data into voltage value data by the DA converter 8 and displaying it on the display means 9, it is possible to make the luminance gradation different for each display method or to display different colors. .

The above operation is performed for each raster synchronization signal,
When the operation is completed for all data for one acquisition (when completed for 500 rasters), the combined waveform for one screen shown in FIG. 3 is displayed.

[0023]

According to the present invention, since the P-P compression display and the actual sample data display are combined and displayed,
It is possible to easily prevent the occurrence of aliasing,
Moreover, it is possible to realize a digital oscilloscope that can express the frequency of a phenomenon by the density of dots.

For example, when the input signal is a pulse signal, as shown in FIG. 4, the waveform is displayed by observing it on a rough time axis without displaying the signal enlarged on the lower stage. It is possible to understand the outline of the waveform even in the state.

[Brief description of drawings]

FIG. 1 is a block diagram showing a hardware configuration of an embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of the embodiment of the present invention.

FIG. 3 is a display screen for explaining the operation of the embodiment of the present invention.

FIG. 4 is a display screen for explaining the operation of the embodiment of the present invention.

FIG. 5 is an explanatory diagram of the operation of aliasing according to the present invention.

FIG. 6 is an explanatory diagram of an operation of a conventional example of the present invention.

FIG. 7 is an explanatory diagram of an operation of a conventional example of the present invention.

FIG. 8 is an explanatory diagram of an operation of a conventional example of the present invention.

[Explanation of symbols]

 1 front end 2 AD converter 3 acquisition controller 4 acquisition memory 5 maximum / minimum value detection means 6 display data generation means 7 display memory 8 DA converter 9 display means 10 display controller 11 microprocessor

Claims (1)

[Claims] 1. An input signal storage means for storing a series of data groups obtained by digitizing an analog input signal, and for each data number required to display one raster among the data stored in the input signal storage means. To read the data, detect the maximum value and the minimum value of the read data, and interpolate the data between the maximum value and the minimum value from the maximum and minimum value detection means. The interpolating means and the display means for synthesizing and displaying the interpolated data from the interpolating means and the data from the input signal storing means are provided, and the interpolating data and the data stored in the input signal storing means are observed simultaneously. A digital oscilloscope characterized by what you can do.