Dynamic characteristics

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Previously we have discussed static characteristics, as there are time-independent characteristics. Dynamics characteristics are traits that change rapidly with time. The input varies instantaneously whereas the output also varies from instant to instant such a system is called a dynamic response of the system. There are two types of dynamic input: Transient and steady-state periodic input. Steady-state periodic input by the name itself refers to input which changes periodically. Transient response is the response which goes to zero as the time becomes large. These characteristics include:

  1. Speed of response
  2. Fidelity
  3. Lag
  4. Dynamic error

Speed of response: Defined as the rapidity with which the device responds to changes in the input. It shows how active and fast the systems are.

Fidelity: The degree to which an instrument is capable of faithfully reproducing the changes in input, without any dynamic error (which is discussed below).

Lag: The time taken by the measurement system to respond to the changes in input. This time is called lag. Lag time varies from system to system. There are two types of lag:

  1. Retardation lag: whenever changes in measured quantity the system begins to respond.
  2. Time delay: The system responds after a dead time once the input is applied. This causes a dynamic error.

Dynamic Error: Difference between the true value of the measured quantity changing with time and the value indicated by the measurement system if no static error is assumed. It is also called measurement error.

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