JPH0150864B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an oscilloscope that displays a ground level along with a waveform on a tube surface.

(Prior art and its problems) Conventional oscilloscopes cannot display the ground level at the same time as the waveform. Therefore, when observing a signal with meaning at the ground level (for example, a logical signal), set the input coupling switch to "GND", align the bright line with a certain position on the screen, and then
The input coupling switch was set to DC coupling and the voltage from ground level was being measured. Therefore, if the emission line position is moved during signal observation, ground level information is lost, and the above-mentioned operation must be performed each time the emission line position is moved.

Further, a cursor function that measures the potential difference between two points of a waveform displayed on a conventional screen is generally known. When using this cursor function to measure voltage from the ground level to any point on the waveform, align one cursor (reference cursor) with the ground level, and move the other cursor (Δ cursor) with the desired point on the waveform. This was done by matching the points. In this case as well, the reference cursor must be aligned with the ground level every time the emission line position is moved, which is a troublesome operation.

(Purpose) In order to solve these drawbacks, the present invention aims to display the ground level at the same time as the waveform, display a Δ cursor, and measure the voltage from the ground level to any point on the waveform. .

(Embodiment) The present invention consists of a switch circuit that switches between an input signal and ground, a sample-and-hold circuit synchronized with this switch circuit, and a connection to the output of an A/D conversion circuit that converts the signal of this sample-and-hold circuit from analog to digital. It consists of an adder circuit that has been added to the adder circuit and a D/A converter circuit connected to the adder circuit, and it is possible to display a Δ cursor that measures the voltage up to an arbitrary point on the waveform as well as the ground level.

The principle of this invention will be explained below using the block diagram of FIG. 1 and the waveform diagram of FIG. 2.
In FIG. 1, a signal input terminal 1 is connected to an amplifier 3 via a switch circuit 2, and the output of the amplifier 3 is connected to a signal switch 4 and a memory circuit 6.
The signal switch 4 alternately switches the outputs of the amplifier 3 and the memory circuit 6 to drive the cathode ray tube. The switch circuit 2, signal changer 4, and memory circuit 6 are connected to a control circuit 7, and operate under the control thereof. Furthermore, the memory circuit 6 is composed of a sample hold circuit 8, an A/D converter 9, an adder circuit 10, a ΔV setting circuit 12 for setting a cursor position at an arbitrary position on the cathode ray tube, and a D/A converter 11. There is.

In the above connection, the control circuit 7 outputs a control signal (FIG. 2c) to intermittently switch the switch circuit 2 to the ground side. The ground level shown in waveform b in FIG.
It is converted into a digital value by the A/D converter 9 stored in the . Note that FIG. 2a shows the input signal waveform. The converted digital value of the ground level passes through the adder circuit 10 and is then input by the D/A converter 11.
The signal is converted into an analog value and applied to the signal switch 4. At this time, the output h of the ΔV setting circuit 12 for a certain period of time
By intermittently applying to the addition circuit 10,
The broken shape shown in FIG. 2d is obtained. The waveform step in FIG. 2d corresponds to the potential difference from the ground level b to the ΔV cursor.

The signal switch 4 alternately switches the output (FIG. 2 d) and the input signal (FIG. 2 a) of the memory circuit 6 and generates a combined signal (FIG. 2 e). In the example shown in FIG. 2, the time ratio between the input signal a and the output d of the memory circuit 6 is 2:1. By applying this signal to the cathode ray tube 5, the waveforms shown in FIG.
Since it corresponds to the signal waveform f, the ground level g, and the ΔV cursor g', by changing the value given to the ΔV setting circuit 12 and aligning the Δ cursor g' to an arbitrary position on the waveform f, the waveform can be changed from the ground level g. The voltage up to any point of f can be determined.

FIG. 3 shows a detailed circuit diagram of an embodiment of the present invention. Input terminal 1 is microcomputer circuit 36
The amplifier circuit 3 is connected to the amplifier circuit 3 via a switch circuit 2 controlled by a control signal 35 from the switch circuit 2. As an example of the amplifier circuit 3, a differential amplifier circuit is used. Amplifier circuit 3
The differential output of transistors 13a, b, 17a,
b, connected to the emitters of transistors 21a and 21b via resistors 20a and 20b. The collectors of the transistors 21a and 21b are connected to the positive power supply V+ via load resistors 22a and 22b, and to the vertical deflection plate of the cathode ray tube 5 and the 2
3a and 23b. The remaining end of the resistor 23a is connected to the positive input of the amplifier 25 and the resistor 24a.
It is connected to ground via. Resistor 23b
The remaining one end of is connected to the output terminal of the amplifier 25 via the negative input of the amplifier 25 and the resistor 24b. The output terminal of the amplifier 25 is connected to the comparator 26
The sample and hold circuit 8 is connected to the positive input of the sample and hold circuit 8. Here, the sample and hold circuit 8 is composed of a switch element 27 and a hold capacitor 28, which are controlled by a control signal 29 from a microcomputer circuit 36. The output of the sample and hold circuit 8 is sent to the comparator 26
is connected to the negative input of The output of the comparator 26 is connected to a microcomputer circuit 36 as a comparison result signal 30. The D/A converter 11 is connected to a microcomputer circuit 36, and the output of the D/A converter 11 is connected to a transistor 33.
connected to the base of b. transistor 33
The collector of transistor b is connected to the connection point between the base of transistor 17b and the collector of transistor 13b via resistor 34b. Transistor 33b
The emitter of the transistor 33a is connected to the emitter of the transistor 33a and the current source 32. Current source 32 is controlled by a control signal 31 from microcomputer circuit 36. Further, the control signal 31 is also connected to the differential amplifier circuit 3, and outputs or cuts the signal depending on the control signal 31. The middle point of the variable resistor 39 is connected to the amplifier 3, and both ends are connected to the positive power source V+ and the negative power source V-, respectively. Both ends of the variable resistor 37 are connected to the positive power supply V+ and the negative power supply V-, respectively.
and its midpoint is connected to the analog input of the microcomputer circuit 36. Also connected to the microcomputer circuit 36 is a switch 38 that is linked to a vertical axis deflection sensitivity switch (not shown) of the oscilloscope.

As described above, the embodiment shown in FIG. 3 is a more realistic circuit based on the principle diagram shown in FIG. 1. That is, for example, in order to configure the A/D conversion circuit 9 and the D/A conversion circuit 11 shown in FIG. 1 with a small number of components, the D/A conversion circuit 11 is
The output of the D/A conversion circuit 11 is applied to the comparator 26 through the passl path shown in FIG. 3 for a certain period of time. It performs an operation corresponding to the A/D conversion circuit 9 shown in FIG.

Furthermore, in FIG. 3, the adder circuit 10 and the ΔV setting circuit 12 shown in FIG. 1 are realized on software by a microcomputer circuit 36. Also, in Fig. 1, ground level detection is taken from the output of amplifier 3, whereas
In the figure, the deflection plate of the cathode ray tube 5 is taken out from the signal line that drives it, but this is because taking out the signal line from the deflection plate with a high signal level improves the S/N ratio and also simplifies the amplification circuit. , are essentially the same.

The control circuit 7 shown in FIG. 1 is realized on software by a microcomputer circuit 36 in FIG.
It is composed of a differential amplifier circuit 3. As described above, it is obvious to those skilled in the art that the principle diagram shown in FIG. 1 can be developed into the embodiment shown in FIG. 3.

In the connection shown in FIG. 3, a signal applied to input terminal 1 is applied to amplifier circuit 3 via switch circuit 2. In the connection shown in FIG. The signal applied to the input terminal 1 in the amplifier circuit 3 is converted into a differential signal, and the transistors 13a,
It is added to the emitter of 13b. transistor 1
The signals amplified by transistors 3a and 13b are amplified to a voltage sufficient to drive the vertical deflection plate of the cathode ray tube 5 by transistors 17a, 17b, 21a and 21b. The variable resistor 39 determines where on the cathode ray tube 5 the waveform is displayed.

Next, a control signal 35 is output from the microcomputer circuit 36, and the switch circuit 2 is switched from the signal side to the ground side. Flowcharts of the operation of this microcomputer circuit 36 are shown in FIGS. 4 and 5.
The signal applied to the differential amplifier circuit 3 is at ground level, and the deflection electrode of the cathode ray tube 5 is applied with a ground level voltage. At this time, the amplifier 25
a, 23b, 24a, and 24b constitute a differential amplifier circuit, so that the differential voltage applied to the two deflection electrodes of the cathode ray tube 5 is obtained as the output of the amplifier 25. The microcomputer circuit 36 outputs the control signal 29 and causes the hold capacitor 28 to store this differential voltage. The voltage stored in this hold capacitor 28 corresponds to the ground level on the cathode ray tube 5. Next, the microcomputer circuit 36 outputs the control signal 31 to turn on the current source 32 and the differential amplifier circuit 3
Turn off the output. When the current source 32 is turned on, the transistors 33a and 33b become active, and the output of the D/A converter 11 is transferred to the transistor 17.
a, 17b and transistors 21a, 21b to the deflection electrode of the cathode ray tube 5, and is applied to a comparator 26 via a differential amplifier constituted by an amplifier 25. The comparator 26 compares the voltage corresponding to the ground level previously stored in the hold capacitor 28 with the output of the D/A converter 11, and sends a comparison result signal 30 to the microcomputer circuit 36. The microcomputer circuit 36 changes the value sent to the D/A converter 11 and reads the ground level stored in the hold capacitor 28. At this time, the D/A converter 11, the comparator 26, and the microcomputer circuit 36 form a generally well-known sequential comparison type A/D conversion circuit. As a result, the microcomputer circuit 36 can know the ground level of the cathode ray tube 5 as numerical data _mG . After a series of these processes, the microcomputer circuit 36 returns the oscilloscope to the normal waveform display mode by releasing the control signals 31 and 39. After writing the ground level data m _G to the D/A converter 11, the ground level can be displayed on the screen together with the waveform by intermittently turning on and off the control signal 31. In addition, by updating the ground level data m _G after a certain period of time using the A/D conversion mode mentioned earlier, even if the bright line position on the tube surface is moved by turning the variable resistor 39, the ground level will be automatically maintained. It is possible to follow the

In the present invention, in addition to the ground line display described above, by setting the output of the D/A converter 11 to, for example, 1 div 400 level, the value obtained from the voltage value of the variable resistor 37 is N, and the ground level Data m _G is alternately output to the D/A converter 11,
By turning on and off the control signal 31, two cursors g and g' can be drawn on the screen as shown in FIG. At this time, ground level data
The cursor obtained by outputting m _G to the D/A converter 11 is the result of the reference cursor (1.1)
If the cursor obtained by outputting is a Δ cursor, then when the variable resistor 37 is turned to bring the Δ cursor to any point on the waveform drawn on the cathode ray tube 5, the value difference between the reference cursor and the Δ cursor, that is, N From −m _G , the value Va from the ground level at any point on the waveform can be found using equation (1.1).

Va=N-m _G /400×(deflection sensitivity) (1.2) (Deflection sensitivity can be obtained from switch 38) (400 is the number of levels per division on the screen surface)
FIG. 5 shows a flowchart for determining the voltage from the ground level to the Δ cursor.

(Effects) The oscilloscope according to the present invention can display the ground level together with the waveform, making it easy to check the ground level, which was a troublesome task in the past.

Furthermore, it is possible to measure voltages from ground level to any point on the waveform.

Further, in the present invention, the detection of the ground level can be taken out from a circuit after the signal switch, that is, a circuit with a large signal level, and those skilled in the art will appreciate that various modifications can be made without departing from the gist of the present invention. It's obvious.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the principle of the present invention, and FIG. 2 shows waveforms of various parts. FIG. 3 is a circuit diagram of an embodiment of the present invention, FIG. 4 is a flowchart when displaying the ground level, and FIG. 5 is a flowchart when calculating the voltage from the ground level to the Δ cursor. 1: Input terminal, 2: Switch circuit, 3: Amplifier, 4: Signal switching circuit, 5: Braun tube, 6: Memory circuit, 7: Control circuit, 8: Sample and hold circuit, 9: A/D converter, 10: Addition circuit, 11:
D/A conversion circuit, 12: ΔV register, 13a,
13b, 17a, 17b, 21a, 21b, 33
a, 33b: transistor, 14, 15, 16,
19, 18a, 18b, 20a, 20b, 22
a, 22b, 23a, 23b, 24a, 24b,
34a, 34b: resistor, 25: amplifier, 26: comparator, 27: switch element, 28: hold capacitor, 38: deflection sensitivity setting switch, 37,
39: variable resistor, 32: current source, 31: control signal (ground level/waveform switching), 35: control signal (GND/signal), 30: comparison result signal, 29: control signal (ground sample).

Claims (1)

[Claims] 1. Switching means for switching between the input signal side and the grounding side, storage means for storing the grounding level when the switching means is on the grounding side, means for converting the stored grounding level into a digital signal, and a means for setting a cursor level corresponding to a cursor position; means for adding a digital signal indicating the cursor level from the setting means to the digital signal indicating the ground level; and converting the digital signal resulting from the addition into an analog signal. and switching means for alternately switching a display screen vertical axis deflection input between the input signal and the ground level cursor level.