Page 333 - The Mechatronics Handbook

16

Introduction to Sensors

and Actuators

M. Anjanappa
University of Maryland Baltimore
County
K. Datta
University of Maryland Baltimore
County 16.1 Sensors
Classification • Principle of Operation • Selection Criteria
T. Song • Signal Conditioning • Calibration
University of Maryland Baltimore 16.2 Actuators
County Classification • Principle of Operation • Selection Criteria

Sensors and actuators are two critical components of every closed loop control system. Such a system is
also called a mechatronics system. A typical mechatronics system as shown in Fig. 16.1 consists of a sensing
unit, a controller, and an actuating unit. A sensing unit can be as simple as a single sensor or can consist
of additional components such as filters, amplifiers, modulators, and other signal conditioners. The
controller accepts the information from the sensing unit, makes decisions based on the control algorithm,
and outputs commands to the actuating unit. The actuating unit consists of an actuator and optionally
a power supply and a coupling mechanism.

16.1 Sensors

Sensor is a device that when exposed to a physical phenomenon (temperature, displacement, force, etc.)
produces a proportional output signal (electrical, mechanical, magnetic, etc.). The term transducer is
often used synonymously with sensors. However, ideally, a sensor is a device that responds to a change
in the physical phenomenon. On the other hand, a transducer is a device that converts one form of
energy into another form of energy. Sensors are transducers when they sense one form of energy input
and output in a different form of energy. For example, a thermocouple responds to a temperature change
(thermal energy) and outputs a proportional change in electromotive force (electrical energy). Therefore,
a thermocouple can be called a sensor and or transducer.

Classification

Table 16.1 lists various types of sensors that are classified by their measurement objectives. Although this
list is by no means exhaustive, it covers all the basic types including the new generation sensors such as
smart material sensors, microsensors, and nanosensors.

©2002 CRC Press LLC