JPH06331658A - Digital oscilloscope - Google Patents

Abstract

PURPOSE:To allow automatic set-up to function even with complex input waveforms so as to stabilize the waveform displayed by counting vertical axis data having the same value, and setting a trigger level where data are sparse. CONSTITUTION:A frequency measuring circuit 9 receives the input of waveform data processed by a display circuit 5, counts the positions of dot clock pulses included in the waveform data, and outputs that count to a trigger level setting means 10. The setting means 10 sets to a trigger level that of the vertical axis data where vertical axes exist at the least frequency, and outputs that data to a trigger circuit 7. The trigger circuit 7 generates a sampling pulse according to the set trigger level, and an input signal is sampled by an S/H circuit 2, A/D converted 3, stored in memory 4, subjected to display processing 5, and displayed 6. Therefore, even in such cases where an automatic set-up function is operated for waveforms where the vertical axis data exist near jitters and maximum and minimum values, observing the waveforms stably is made possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital oscilloscope, and more particularly to a digital oscilloscope having an improved method of determining an optimum trigger level in an automatic measurement setting function (so-called auto setup function).

[0002]

2. Description of the Related Art In a conventional digital oscilloscope, a trigger level for operating an automatic measurement setting function (hereinafter referred to as an auto setup function) is determined by a maximum value and a minimum value of sampled input signals. The value between the values was used as the trigger level. As described above, since the trigger level is uniquely determined, when there is a large amount of input signal data in the portion of the value determined as the trigger level, as in the case where the waveform as shown in FIG. 3 is input. For example, if the input waveform has a large jitter, or if the pulse waveform is complicated, the trigger is applied more than necessary, and the displayed waveform becomes unstable.

[0003]

SUMMARY OF THE INVENTION The present invention solves this problem and provides a digital oscilloscope that enables a stable trigger level to be set based on the auto setup function even with a complicated input waveform. Aim to achieve.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a digital oscilloscope for digitally converting an analog input signal and displaying a waveform, and in a display of one screen, vertical axis data having the same value on the display screen. A digital oscilloscope characterized by having a vertical axis frequency measuring circuit that counts how many there are and trigger level adjusting means for adjusting the trigger level based on the output from the vertical axis frequency measuring circuit. is there.

[0005]

[Function] Since there is little data existing in the input signal and the trigger level is selected, a stable trigger level can be set based on the auto setup function even with a complicated input waveform. Becomes

[0006]

1 is a block diagram of an embodiment of the present invention.
In the figure, reference numeral 1 denotes an input amplifier, which is specifically configured by an attenuator or the like that receives an input signal. Reference numeral 2 denotes a sample-hold circuit (hereinafter referred to as S / H circuit), which samples an input signal by a sampling pulse output from the trigger circuit 7. Reference numeral 3 denotes an analog / digital converter (hereinafter referred to as an A / D converter), which performs analog / digital conversion on the output from the S / H circuit 2. A data memory 4 stores the digital output from the A / D converter 3. 5
Is a display processing circuit, which performs arithmetic processing of the digital output from the data memory 4, converts it into display data, and outputs a video signal. Reference numeral 6 denotes a display, which displays a waveform based on the output from the display processing circuit 5. Reference numeral 7 is a trigger circuit, which outputs a sampling pulse based on the signal from the trigger level setting means 10. A counter 8 outputs an address to be accessed in the data memory 4. Reference numeral 9 denotes a frequency measuring circuit, which measures, based on the data read from the data memory 4, which data and how much exist in the display waveform for one screen. Reference numeral 10 is a trigger level setting means, which calculates and outputs which level is the display level based on the information from the frequency measuring circuit 9. The trigger level setting means 10 is specifically operated by a CPU or the like.

The operation in such a configuration will be described.
First, because of the auto setup function, the trigger circuit 7 generates a sampling pulse when the input signal reaches a certain arbitrary time or a value set arbitrarily. By this sampling pulse, the S / H circuit 2
Then, the input signal is sampled, and the analog / digital converted data is stored in the data memory 4 at an address corresponding to the time axis on the display screen. The contents of the data memory 4 are converted into a video signal by the display processing circuit 5 and displayed on the display 6. When the data for display is output to the display processing circuit 5, it is also output to the frequency measuring circuit 9.

The frequency measuring circuit 9 detects how many values exist in the vertical axis data for one screen. This is composed of software or a hardware circuit composed of a plurality of digital comparators and counters. As a specific operation, the waveform data processed as data for display in the display circuit 5 is input, and the position of the dot clock pulse of the waveform data is counted to find out which data is the most. You will be counting things. Further, the data read from the data memory 4 may be used as it is. Such a detection result is usually recognized as a histogram display as shown in FIG. 2 or FIG. Information on the number of pieces of data is output to the trigger level setting means 10. Trigger level setting unit 10, among the vertical-axis data in the range of V _PP displayed waveforms shown in FIG. 2, in surrounded by frequently appearing part of the vertical axis (V _P-P2), the most power A small number is set as a trigger level determined by operating the auto setup function and output to the trigger circuit 7.

Therefore, of the input signals having the repetitive waveform, it is possible to set the trigger level to be between the maximum value and the minimum value of the waveform and the frequency of the input waveform data is the least.

[0010]

As described in detail above, according to the present invention, by setting the trigger level at the place where the frequency of the vertical axis data is small, the vertical axis can be set near the center value of jitter or the maximum value and the minimum value. It is possible to determine a trigger level that enables stable waveform observation even when the auto-setup function is operated, based on a waveform for which data exists.

This will be specifically described. The level set by the conventional auto setup function is shown in Fig. 2.
It is the level shown in (1) of 3. At this level, the display waveform becomes unstable because there are many identical values in the input signal. On the other hand, according to the present invention, the level shown in (2) of FIGS. 2 and 3 in the place with the smallest frequency is set as the trigger level in the middle (V _P-P2 ) surrounded by the places with the highest frequency on the vertical axis. To be done. Therefore, a stable display waveform can be obtained.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of the operation of the embodiment of the present invention.

FIG. 3 is an explanatory diagram of the operation of the embodiment of the present invention.

[Explanation of symbols]

 1 Input Amplifier 2 S / H Circuit 3 A / D Converter 4 Data Memory 5 Display Processing Circuit 6 Display 7 Trigger Circuit 8 Counter 9 Frequency Measurement Circuit 10 Trigger Level Setting Means

Claims (1)

[Claims] 1. A digital oscilloscope for converting an analog input signal into a digital signal and displaying a waveform, in a single screen display, a vertical axis for counting the number of vertical axis data having the same value on the display screen. A digital oscilloscope provided with an axis frequency measuring circuit and a trigger level adjusting means for adjusting a trigger level based on an output from the vertical axis frequency measuring circuit.