How Oscilloscopes Generate Positive and Negative Pulses with Varying Widths

In electronic measuring instruments, oscilloscopes are undoubtedly a favorite among electronic engineers, as they visually display the waveform of electrical signals and generate pulse signals. When using an oscilloscope, various issues may arise, one of which is how to generate positive and negative pulse signals with different widths. How can this be done?

1. Set Oscilloscope Parameters

Turn on the oscilloscope and set the horizontal time base (e.g., 1ms/div) and vertical voltage range (e.g., 5V/div) to accommodate the amplitude and frequency of the signal being tested.

2. Select Trigger Mode

Use the pulse width trigger mode (PW Trigger), which allows triggering the display of the signal based on pulse width.

3. Set Pulse Width Trigger Conditions

For positive pulses, set the trigger condition to “greater than positive pulse width” or a specific value (e.g., 500us) to capture positive pulses wider than that value. For negative pulses, select “less than negative pulse width” or the corresponding value (e.g., -300us) to capture negative pulses narrower than that value. Note: The negative pulse width value may be set as a positive value in practice, but it represents the width of the negative pulse.

4. Adjust Trigger Level

Set an appropriate trigger level to ensure that the rising or falling edge of the pulse signal can trigger the display; the trigger level for positive and negative pulses may need to be set separately.

5. Generate Signal

If the oscilloscope has a signal generation function, it can directly set to generate positive and negative pulse signals with specified widths. If this function is not available, an external signal source is required, and the above settings should be used to capture and analyze the signal. Example reference: Positive pulse width setting: greater than 500μs; Negative pulse width setting: less than -300μs (which may be represented as a positive value, such as 300μs, but indicates a negative pulse). Horizontal time base: 1ms/div; Vertical voltage range: 5V/div.