Trigger type: leading or trailing edge.
Posted: Tue Feb 18, 2025 4:16 am
To obtain a stationary image on the screen, each subsequent beam trajectory across the screen in the scanning cycles must run along the same curve. This is ensured by the scanning synchronization circuit, which starts the scanning at the same level and front of the signal being studied.
Example. Let's say a sinusoidal signal is being examined and the loan data circuit is configured to start the sweep when the sinusoid rises, when its value is zero. After the start, the beam draws one or more, depending on the configured sweep speed, sinusoidal waves. After the sweep is complete, the synchronization circuit does not start the sweep again, as in the automatic mode, but waits for the sinusoidal wave to pass through the zero value on the rising edge again. Obviously, the subsequent passage of the beam across the screen will repeat the trajectory of the previous one. At sweep repetition rates above 20 Hz, due to the persistence of vision, a motionless picture will be visible.
If the start of the sweep is not synchronized with the observed signal, the image on the screen will look "running" or even completely smeared. This happens because in this case, different sections of the observed signal are displayed on the same screen.
To obtain a stable image, all oscilloscopes contain a system called a synchronization circuit, which in foreign literature is often incorrectly called a trigger.
The purpose of the timing circuit is to delay the start of the sweep until some event occurs. In the example, the event was the sine wave crossing zero on the rising edge.
Therefore, the synchronization scheme has at least two settings available to the operator:
Trigger level: sets the voltage of the signal being analyzed, upon reaching which the sweep is started.
Proper adjustment of these controls ensures that the sweep always starts at the same point in the signal, so that the signal image on the oscilloscope appears stable and motionless.
Example. Let's say a sinusoidal signal is being examined and the loan data circuit is configured to start the sweep when the sinusoid rises, when its value is zero. After the start, the beam draws one or more, depending on the configured sweep speed, sinusoidal waves. After the sweep is complete, the synchronization circuit does not start the sweep again, as in the automatic mode, but waits for the sinusoidal wave to pass through the zero value on the rising edge again. Obviously, the subsequent passage of the beam across the screen will repeat the trajectory of the previous one. At sweep repetition rates above 20 Hz, due to the persistence of vision, a motionless picture will be visible.
If the start of the sweep is not synchronized with the observed signal, the image on the screen will look "running" or even completely smeared. This happens because in this case, different sections of the observed signal are displayed on the same screen.
To obtain a stable image, all oscilloscopes contain a system called a synchronization circuit, which in foreign literature is often incorrectly called a trigger.
The purpose of the timing circuit is to delay the start of the sweep until some event occurs. In the example, the event was the sine wave crossing zero on the rising edge.
Therefore, the synchronization scheme has at least two settings available to the operator:
Trigger level: sets the voltage of the signal being analyzed, upon reaching which the sweep is started.
Proper adjustment of these controls ensures that the sweep always starts at the same point in the signal, so that the signal image on the oscilloscope appears stable and motionless.