JPS6247087Y2 - - Google Patents

Description

[Detailed description of the invention] The invention relates to a sweep circuit of an oscilloscope.
In particular, the present invention relates to improvements in auto-trigger circuits that can perform free-run sweeps stably in alternate trigger operations.

Traditionally, one type of oscilloscope sweep mode is alternate sweep, that is, multiple signals, e.g.
A mode in which signals are alternately swept is known. Generally, in alternate sweep mode, two signals are displayed alternately every sweep in synchronization with the trigger signal, and at different positions in the Y-axis direction of the cathode ray tube, making it appear as if two signals were being displayed simultaneously. I am trying to display it. By the way, in such a sweep mode, an alternate trigger circuit is conventionally known that switches trigger signals corresponding to each channel and supplies them to a synchronization circuit to synchronize the sweep with each channel. However, only one automatic signal generation circuit was provided, which determines the presence or absence of a trigger signal and determines whether the sweep is in a free running state or triggered sweep. For this reason, in a two-channel oscilloscope, a trigger signal can be obtained from one channel, but a trigger signal cannot be obtained from the other channel, and problems arise when sweeping is performed at a relatively high speed.

In other words, when a channel from which a trigger signal cannot be obtained is selected, the system waits for a trigger signal to arrive for a certain period of time, and even after this certain period of time has elapsed,
Additionally, auto-sweep is started when a trigger signal cannot be obtained. For this reason, during the above-mentioned period of time,
The display becomes dormant, which causes the display to flicker.

Figure 1 is a block diagram showing an example of such an oscilloscope auto trigger circuit.
The signals given to a, 1b are sent to preamplifiers 2a, 2
The signal is amplified by b, selected by the vertical switch 3, amplified by the vertical output amplifier, and applied to the vertical deflection plate of the cathode ray tube. Further, a trigger signal taken out from the output side of the preamplifiers 2a, 2b via trigger pick-off circuits 4a, 4b is selected via a trigger switch 5, and is applied to a trigger generator 6. This trigger generator 6 generates a trigger pulse when the change direction and level of the trigger signal satisfy predetermined conditions, and supplies it to a sweep section 7 to generate a sweep signal. Apply to the deflection plate. Further, reference numeral 8 denotes an auto signal generator which outputs an auto signal forcibly when the trigger generator 6 cannot detect a trigger signal or in response to an external operation, causing the sweep section 6 to enter a self-sweeping state. In other words, it is operated by free run sweep.

However, in this type of device, even when the sweep section 6 is triggered and swept using a trigger signal with a long repetition period, the auto signal generator 7 outputs the auto signal prematurely and the sweep section 6 self-sweeps. It is necessary to operate with a relatively long time constant so that the state does not change. For this reason, if you perform an alternate sweep when a trigger signal is obtained from one channel but not from the other channel, for example, when the other channel is selected during a medium-speed sweep, the auto Because the time constant of the signal circuit is set long, the response until the self-sweeping state is reached is slow, which causes the display image on the cathode ray tube to flicker, causing problems in observation. Furthermore, when high-speed sweeping is performed under such conditions, there is a problem in that the proportion of time during which bright lines appear on the cathode ray tube surface decreases, resulting in a decrease in brightness.

For this purpose, for example, as shown in FIG. 2, trigger generators 6a, 6b...6n and auto signal generators 8
a, 8b...8n are provided, and trigger generators 6a, 6b are provided.
. . 6n is selected by the trigger switch 9, and the outputs of the auto signal generators 8a, 8b, .

However, with this type of device, the number of circuit components increases significantly as the number of channels increases, resulting in problems such as increased costs and an increased failure rate.Furthermore, the trigger level must be set for each channel. It has the disadvantage that it is difficult to operate.

This idea was made in view of the above circumstances.
Equipped with an auto signal generation circuit that has the function of resetting the auto signal at high speed and an auto signal holding circuit that holds the auto signal provided for each channel for a certain period of time, the trigger level of each channel can be set at once, and the parts It is an object of the present invention to provide an auto-trigger circuit that has a small number of points, can stably perform an alternate trigger operation, and can reliably perform an alternate sweep.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the block diagram shown in FIG. 3, in which the same parts as in FIGS. 1 and 2 are given the same reference numerals. In this embodiment, an n-channel auto circuit will be explained.
In the figure, reference numeral 11 denotes an auto signal generator which has a function of quickly resetting the output using the reset switch 1. The reset switch 12 is closed each time an input signal is selected, thereby resetting the output of the auto signal generator. The output of the auto signal generator 11 is transferred to the corresponding auto signal holding circuits 14a, 14b, . . . 1 by the first auto signal switch 13.
Give to 4n. And auto signal holding circuit 14
Outputs of channels a, 14b, .

With such a configuration, when performing an alternate sweep, the vertical switch 3, the trigger switch 5, and the first
The automatic signal changer 13 and the second automatic signal changer 15 each perform a switching operation in synchronization with the sweep cycle of the sweep section 7, and each time the switching operation is performed, the reset switch 12 is closed and the auto signal generator is switched on. 11
Reset.

The output of the preamplifier 2 selected by the vertical switch 3 is applied to the vertical deflection plate of the cathode ray tube via an amplifier (not shown). Further, the output of the trigger pick-off circuit 4 is sent to the trigger generator via the trigger switch 5, and when the level corresponding to the setting value of the trigger level setter 16 and the direction of change satisfy the set conditions, the trigger pulse is sent to the sweep section 7. A sweep signal is generated and applied to the horizontal deflection plate of the cathode ray tube via an amplifier (not shown). Further, when the trigger generator 6 cannot detect a trigger signal, or in response to a forced operation from the outside, the auto signal generator 11 is activated to output an auto signal. This auto signal is transferred to one of the corresponding auto signal holding circuits via the first auto signal switch 13.
Give and hold.

FIG. 4 is a circuit diagram showing a specific example of the auto signal generator 11, the first and second auto signal switchers 13, 15, and the auto signal holding circuits 14a, 14b, . . . 14n. In other words, the auto signal generator 11 is composed of a mono multivibrator having a clear terminal CLR, and the output of the trigger generator 6 is connected to the clock terminal.
CK, and an "L" level signal from the reset switch 12 is given to the clear terminal CLR. Then, set the output pulse width to the R/C terminal and C
A predetermined width is set by a capacitor C and a resistor R1 connected to the terminal. The output is then applied in parallel to the first automatic signal switch 13 via a diode in the opposite direction. The output of the first auto signal switch 13 is applied to one end of each capacitor constituting the second auto signal switch 15 and the auto signal holding circuits 14a, 14b...14n, and the other ends of the capacitor are connected to a common potential. . Note that the first and second auto signal switchers 13 and 15 use switching signals CH that do not overlap.
1, CH2...This is an analog switch that is selectively turned on by CH _o . The output of the second automatic signal switch 15 is connected in parallel and applied to the sweep section, and this common connection point is connected to the power supply +V via a resistor R2.

FIG. 5 is a waveform diagram illustrating the operation of the circuit shown in FIG. 4. A reset signal RES applied from the reset switch 12 becomes "L" every time a channel is switched and resets the mono multivibrator. Therefore, when a trigger signal is obtained, a signal of "L" level is given from the trigger generator 6, the output becomes "L", the charge in the capacitor of the auto signal holding circuit 14 is discharged, and the signal is sent to the sweep section 7. L”
Apply a level signal and perform a trigger sweep. When the trigger signal cannot be obtained, the output becomes "H" and the terminal voltage of the capacitor gradually increases. When this voltage reaches a predetermined voltage after a predetermined period of time, the sweep section 7 is energized to be in a self-running state and free-run sweep is performed. Here, auto signal holding circuit 14
A capacitor is provided for each channel, and the corresponding capacitor is selected according to the switching operation of the channel, so if a capacitor with a high terminal voltage is selected, that is, a capacitor corresponding to a channel from which a trigger signal cannot be obtained, the free run is immediately started. Sweeping is performed and the display can operate stably without flickering.

However, in Fig. 3, the auto signal holding circuit 1
The outputs of 4a, 14b, . Here, the auto signal holding circuits 14a, 14b...14n hold the auto signals from the previous sweep, so as soon as a channel is selected for auto sweeping, the sweep unit 7 is activated to perform auto sweeping again. This prevents display flickering and ensures stable operation.

Furthermore, compared to the one shown in FIG. 2, the trigger generator 6 and auto signal generator 11 each need only one channel, so the configuration is significantly simpler. In particular, the auto signal holding circuit 14 provided for each channel can be configured with, for example, one capacitor, and the number of components can be significantly reduced compared to a configuration in which a trigger generator and an auto signal generator with complicated configurations are provided for each channel. Cost reduction can be achieved. Furthermore, since a single trigger generator 6 is used, the trigger level can be set for all channels at once, resulting in good operability, which is particularly advantageous in multi-channel oscilloscopes.

As described above, the present invention is provided with an auto signal generator that resets the auto signal every time the channel is switched and an auto signal hold circuit that holds the auto signal for each channel, so that the alternate trigger operation can be performed stably and flickering of the display can be prevented.
The circuit configuration is simple, the cost can be reduced, and a sweep circuit suitable for a multi-channel configuration can be provided.

[Brief explanation of the drawing]

1 and 2 are block diagrams showing different conventional sweep circuits, FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG. 4 is a circuit diagram of the main part of the above embodiment.
FIG. 5 is a waveform diagram illustrating the operation of the circuit shown in FIG. 4. 1a, 1b...1 _o ...Input terminal, 2a, 2b...
2 _o ...Preamplifier, 3... Vertical switch, 4a,
4b...4 _o ...Trigger pick-off circuit, 5...Trigger switch, 6...Trigger generator, 7...Sweep section, 11...Auto signal generator, 12...Reset switch, 13...First auto signal Switch, 1
4a, 14b...14n...Auto signal holding circuit,
15...Second auto signal switch.

Claims (1)

[Scope of utility model registration request] In a sweep circuit that performs an alternate sweep on signals of multiple channels, a vertical switch selectively supplies a signal of each channel to a vertical amplifier;
a trigger pick-off circuit provided for each channel to obtain a trigger signal from the signal of each channel; a trigger generator to which the trigger signal obtained by the trigger pick-off circuit is applied via a trigger switch linked to the vertical switch; An auto signal generator with a reset function that is energized and outputs an auto signal when the trigger signal cannot be detected by the trigger generator, and an auto signal holding circuit provided corresponding to each channel in conjunction with the vertical switch mentioned above. a first auto signal switch that provides the auto signal;
A free run sweep is performed by an auto signal given from the auto signal holding circuit via a second auto signal switch linked to the vertical switch, and the vertical switch and trigger switch are performed in synchronization with the sweep operation of each channel. 1. A sweep circuit comprising: a sweep section that switches between the automatic signal generator and the first and second auto signal changers; and a reset switch that resets the auto signal generator each time the sweep section switches.