JPH0766012B2 - Waveform display device - Google Patents

Description

The present invention relates to a waveform display device such as an oscilloscope, and more particularly to a reference level display.

<Prior art> For example, when performing waveform observation with an oscilloscope,
In many cases, the relationship between the measured waveform and the reference level such as the earth potential is obtained.

However, since the measurement waveform is displayed on the display screen, and the reference level is not displayed, the observer must measure the reference level as necessary and grasp the display position on the display screen at that time. And the operability is poor.

In order to solve such a problem, a certain type of waveform display device displays a reference level position as a graphic symbol on a part of the display screen.

<Problems to be Solved by the Invention> However, in order to display the reference level position by the graphic symbol, a display processing circuit different from the waveform display processing needs to be additionally provided, and the circuit configuration becomes complicated.

The present invention focuses on such a point, and an object thereof is to provide a waveform display device capable of displaying the position of the reference level on the same display screen as the measured waveform with a relatively simple configuration. .

<Means for Solving the Problems> A waveform display device of the present invention converts a measured waveform into a digital signal and stores it in a memory, and a large number of display elements are two-dimensionally arranged according to the waveform data stored in the memory. In the waveform display device for driving the display, the changeover switch for selecting the input signal and the reference level, the adder to which the output of this changeover switch is added to one input terminal, and the other input terminal of this adder A D / A converter whose output is added to, an A / D converter that converts the output of the adder into a digital signal, and the reference level position data and measurement waveform data output from this A / D converter. A memory that stores data continuously from the address corresponding to one end to the address corresponding to the other end of the display area of the display unit, and one input terminal to which each data read from this memory is added A digital adder, means for adding offset data to the other input terminal of the digital adder and the D / A converter, and data read from the memory is added to one input terminal and the other input terminal A selector to which the output of the digital adder is added, and controlling read and write operations of the memory,
Means for controlling the selector so that the output of the digital adder is output in the section where the reference level position data is read from the memory and the data read from the memory is output in the other section; A display for displaying the output of the selector, wherein the reference level position data and the measured waveform data stored in the memory are simultaneously displayed as continuous waveform data along the time axis of the display, It is characterized in that the entire display waveform is moved in the vertical direction according to the offset data.

<Operation> In the present invention, the position of the reference level is simultaneously displayed on the display unit as a part of the display waveform together with the measured waveform, and a special display processing circuit for performing processing for displaying the position of the reference level is It becomes unnecessary.

Further, by adjusting the vertical position by changing the digital offset data to increase or decrease the offset voltage, the entire display waveform including the reference level waveform and the measurement waveform can be moved in the vertical direction.

<Example> Hereinafter, an example of the present invention is described in detail using a drawing.

FIG. 1 is a configuration explanatory view showing an embodiment of the present invention.
In the figure, reference numeral 1 is an input selector switch, and an input signal V
_{An example in} which _in and the ground potential V _G are selectively switched and output to one input terminal of the adder 3 is shown. The changeover switch 1 is switched and driven by a control signal k output from the operation control circuit 9. Reference numeral 2 is a D / A converter for adding an offset voltage to the output signal of the changeover switch 1, and its output signal a is input to the other input terminal of the adder 3. An A / D converter 4 converts the analog output signal b of the adder 3 into a digital signal c. The output data c of the A / D converter 4 is stored in the memory 6 via the memory control circuit 5. The memory control circuit 5 controls a read / write operation of the data d in the memory 6, and a control signal h for controlling the selector 7 in synchronization with the read / write operation.
Is input to the select terminal S of the selector 7. The data e read from the memory 6 is input to one input terminal A of the selector 7 and one input terminal of the digital adder 8 via the memory control circuit 5. Offset data f is input from the operation control circuit 9 to the other input terminal of the digital adder 8. This offset data f is also input to the D / A converter 2. The output data g of the digital adder 8 is input to the other input terminal B of the selector 7. The output data i of the selector 7 is input to the display control circuit 10, and the output data j of the display control circuit 10 is output.
Is input to the display 11 such as a CRT.

The operation of the apparatus thus configured will be described.

First, the changeover switch 1 is connected to the ground potential V _G side. As a result, the input signal b of the A / D converter 4 becomes the offset voltage V _OS output from the D / A converter 2. This offset voltage V _OS is converted into a digital signal c by the A / D converter 4.
The output data c of the A / D converter 4 is displayed on the display 11 from the address 0 of the memory 6 corresponding to the left side of the display area of the display 11 via the memory control circuit 5 as shown in FIG. It is stored in the area up to the address N corresponding to the right end of the area. The memory control circuit 5 reads the data d stored in the memory 6 after writing the data d of the offset voltage V _{OS to} the memory 6, inputs the read data e into the selector 7, and The control signal h is controlled so as to be input to the display control circuit 10.

As a result, the level of the ground potential V _G is displayed on the display 11 as shown in FIG. The operation of writing and reading the data d of the offset voltage V _OS to and from the memory 6 is constantly repeated, and the data f of the offset voltage V _OS output from the operation control circuit 9 is changed to display The position of the waveform displayed on the container 11 moves vertically.

Next, connect the change-over switch 1 in the input signal V _in side. As a result, the output signal b of the adder 3 becomes V _in + V _OS . The output signal b (V _in + V _OS ) of the adder 3 is converted into a digital signal c by the A / D converter 4. The output data c of the A / D converter 4 is stored in the memory 6 via the memory control circuit 5, and the storage area is a measurement waveform display area of the display 11 by the memory control circuit 5 as shown in FIG. The area from the address S corresponding to the left end of the display area to the address N corresponding to the right end of the display area of the display unit 11 is controlled. That is,
The reference level data based on the ground potential V _G is stored from address 0 to address S of the memory 6, and the address S
The measured waveform data based on the input signal V _in is stored from the address to the address N. The memory control circuit 5 is
After the writing of the data d of (V _in + V _OS ) to the memory 6, the data d stored in the memory 6 is read and the read data e is input to the selector 7, and this data e is also displayed. The control signal h is controlled so as to be input to the.

As a result, as shown in FIG. 3, the display 11 continuously displays the level of the ground potential V _G and the measured waveform based on the input signal V _in as a continuous waveform along the time axis direction. It will be.

When the offset voltage V _OS is changed while the data e is being output from the selector 7, the measured waveform based on the input signal V _in changes in the vertical direction, but the waveform based on the ground potential V _G does not change. Therefore, the added data g of the output data e of the memory and the digital offset data f is obtained from the digital adder 8, and the memory control circuit 5 causes the memory 7 to select the digital adder from the selector 7 in the section from address 0 to address S of the memory 6. 8 so that the output data g of 8 is output.
The control signal h sent to the select terminal S of is inverted.

As a result, the waveform based on the ground potential V _G stored in the section from the address 0 to the address S of the memory 6 is also changed in the vertical direction according to the change in the offset voltage V _OS , similarly to the measured waveform based on the input signal V _in. Therefore, the entire display waveform can be moved in the vertical direction by adjusting the vertical position by increasing or decreasing the offset voltage V _OS . D /
The gains of the A converter 2 and the adder 3 are set to 1.

FIG. 4 is an explanatory diagram showing a specific example of the memory 6. Conventionally, generally, the scale of the horizontal axis (time axis) of the oscilloscope is set to 10 scales. Here, assuming that the display resolution in the horizontal axis direction of the digital oscilloscope is 50 dots per scale, the total number of display dots along the horizontal axis direction is 501. On the other hand, it is convenient to process digital memory with binary data. Therefore, when using 512 bytes as the memory 6, for example, as shown in FIG. 4, an area of 501 bytes is used for displaying the measured waveform, and the address 0 out of the 11 bytes from the remaining head is used. The reference level position may be displayed by storing the initial value of the ground potential V _G at addresses 9 to 9.

By the way, as described above, the initial value of the ground potential V _G is set to A / D.
Although it is the converted data, this is the actual input signal
The offset voltage V _OS applied to V _in is based on the fact that the offset voltage of the D / A converter 2 and the adder 3 is also superposed and therefore does not exactly match the digital offset data f. In addition, the gains of the D / A converter 2 and the adder 3 may not be exactly 1 in some cases, and a non-linear error of the D / A converter 2 may be considered. Therefore, the initial values are stored in the memory 6 as these offset errors being dominant.
A / D converted data is used, and subsequent vertical position adjustment is performed by adding digital offset data f.

When such an analog error Δε is known, the operation control circuit 9 outputs the digital offset data f to the D / A converter 2 to output the digital adder, as shown in FIG. Digital offset data f ′ (f ′ = f + Δε) to which the analog error Δε is added may be output to 8.

With such a configuration, it is sufficient to handle the reference data position as display data, and a special display circuit for displaying a graphic symbol as in the conventional art is not required.
As a new digital processing circuit, a digital adder,
A selector and selector control signal generating means are required,
These can be realized relatively inexpensively as a gate array circuit.

Further, in the above embodiment, the example in which the ground potential is used as the reference level is shown, but other reference potentials may be used depending on the application.

Further, the display is not limited to the CRT and may be a flat display such as a liquid crystal display.

<Effects of the Invention> As described above, according to the present invention, it is possible to realize a waveform display device capable of displaying the position of the reference level on the same display screen as the measured waveform with a relatively simple configuration, and practical effects Is big.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment of the present invention, FIGS. 2 and 3 are operational explanatory views of FIG. 1, FIG. 4 is a specific example of a memory in FIG. 1, and FIG. It is a structure explanatory view of the important section of other examples of the present invention. 1 ... Input selector switch, 2 ... D / A converter, 3 ... Adder, 4 ... A / D converter, 5 ... Memory control circuit, 6 ...
... Memory, 7 ... Selector, 8 ... Digital adder, 9
…… Operation control circuit, 10 …… Display control circuit, 11 …… Display unit (CRT).

Claims (1)

[Claims] 1. A waveform display device for converting a measured waveform into a digital signal, storing it in a memory, and driving a display in which a large number of display elements are two-dimensionally arranged according to the waveform data stored in the memory, A selector switch for selecting the input signal and the reference level, an adder whose output is applied to one input terminal, and a D / A converter whose output is applied to the other input terminal of this adder, The A / D converter that converts the output of the adder into a digital signal, and the reference level position data and measured waveform data output from this A / D converter are output from the address corresponding to one end of the display area of the display. A memory that stores data continuously up to the address corresponding to the other end, a digital adder to which each data read from this memory is added to one input terminal, and the other of this digital adder Means for adding offset data to the input terminal and the D / A converter, and a selector to which the data read from the memory is added to one input terminal and the output of the digital adder is added to the other input terminal And controlling the read and write operations of the memory,
Means for controlling the selector so that the output of the digital adder is output in the section where the reference level position data is read from the memory and the data read from the memory is output in the other section; A display for displaying the output of the selector, wherein the reference level position data and the measured waveform data stored in the memory are simultaneously displayed as continuous waveform data along the time axis of the display, A waveform display device, characterized in that the entire display waveform is moved in the vertical direction according to the offset data.