Question

a) Define: rise time, peak over shoot and settling time. b) Explain about the time constant of first order system.

Answer 1

a) Answer- Rise time- Rise time is the time taken by a signal to change from a specified low value to a specified high value. These values may be expressed as ratios or equivalently, as percentages with respect to a given reference value. For example, for an overdamped signal, the rise time is the time to reach the signal response from its 10% to 90% of the final value.

Peak overshoot- The time required by the response to reach its first peak value. It is also called the maximum overshoot. The overshoot is the maximum amount by which the response overshoots the steady-state value and is thus the amplitude of the first peak.

Settling time- It is the time required for a response to become steady. It is the time for a response to reach 98% of its final value and remains in steady-state. It is generally 4 times the time constant of the signal.

b) Answer- Time constant is the time by which the step response reaches 63.2% of the final value. Note that this is for a step input i.e. input signal is a unit step signal. Time constant implies the system speed to reach the final value. Smaller the time constant, faster the response of the system.