Chp. 1 Review Questions Flashcards
What are the main components of a feedback control system?
The process, the actuator, the sensor, and the controller.
What is the purpose of the sensor?
To measure the output variable and, usually, to convert it to an electrical voltage.
Give three important properties of a good sensor.
A good sensor is linear (the output is proportional to the input signal) over a large range of amplitudes and a
large range of frequencies at its input, has low noise, is unbiased, is easy to calibrate, and has low cost. The
relative values of these properties varies with the particular application.
What is the purpose of the actuator?
The actuator takes an input, usually electrical, and converts it to a signal such as a force or torque that causes the
process output to move or change over the required range.
Give three important properties of a good actuator.
A good actuator has fast response, and adequate power, energy, speed, torque, and so on, to be able to cause the
process output to meet the design specifications and is efficient, lightweight, small, cheap, and so on. As with
sensors, the relative value of these properties varies with the application.
What is the purpose of the controller? Give the input(s) and output(s) of the controller.
The controller is to take the sensor output (the input to the controller) and compute the control signal (the output
of the controller) to be sent to the actuator.
What physical variable(s) of a process can be directly measured by a Hall effect sensor?
A Hall-effect device measures the strength of a magnetic field and can be most easily configured to measure
relative positions of two bodies or relative angles.
What physical variable is measured by a tachometer?
tachometer measures speed of rotation or angular velocity.
Why do most sensors have an electrical output, regardless of the physical nature of the variable being measured?
Electrical signals are the most easily manipulated; therefore, most controllers are electrical devices, either analog
or digital. To provide the signal input to such a device, the sensor needs to produce an electrical output.
