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Time measurements at a pulse

Figure 1: Definitions for time measurement at a pulse

Overshoot
Droop
Pulse Width
Baseline
Rise Time
Fall Time
Undershoot

Figure 1: Definitions for time measurement at a pulse

Time measurements at a pulse

Time measurements at a pulse may be performed with an oscilloscope. Oscilloscopes have calibrated scales and also time marks. The best-known term here is pulse duration. However, pulses very rarely have an ideal rectangular shape. Due to the influences of real and imaginary loads, they have a smoothed pulse shape (pulse distortion). It is then necessary to know at which point of the pulse to measure.

Pulse width

The duration of a pulse is defined from the center of the rising edge to the center of the falling edge. More precisely: at the points with 50% of the maximum amplitude (without overshoot and undershoot).

Rise time and fall time

The rise time is measurable between the defined intermediate values of 10% and 90% at the level change. The shorter this time is, the better the slope of the pulse.

Overshoot

Overshoot occurs when the voltage does not reach the desired value directly but overshoots the setpoint. Overshoot can be expressed as a percentage of the maximum voltage. In Figure 1, for example, this would be about 35%.

Undershoot

The voltage could drop below the setpoint at the end of a pulse. A diode can limit this (negative shunt limiter).

The droop of the pulse roof

Due to the influence of the load, the pulse roof can also slope slightly downwards. However, a measurement results in a voltage value. It is measured between 10% and 90% here of the duration of the pulse roof.