Page 335 - The Mechatronics Handbook

TABLE 16.1 Type of Sensors for Various Measurement Objectives (Continued)
Sensor Features
Infrared type Noncontact point sensor with resolution limited by wavelength
Infrared thermography Measures whole-field temperature distribution
Proximity sensors
Inductance, eddy current, hall effect, Robust noncontact switching action
photoelectric, capacitance, etc. The digital outputs are often directly fed to the digital controller
Light sensors
Photoresistors, photodiodes, photo Measure light intensity with high sensitivity
transistors, photo conductors, etc. Inexpensive, reliable, and noncontact sensor
Charge-coupled diode Captures digital image of a field of vision
Smart material sensors
Optical fiber
As strain sensor Alternate to strain gages with very high accuracy and bandwidth
Sensitive to the reflecting surface’s orientation and status
As level sensor Reliable and accurate
As force sensor High resolution in wide ranges
As temperature sensor High resolution and range (up to 2000∞C)
Piezoelectric
As strain sensor Distributed sensing with high resolution and bandwidth
As force sensor Most suitable for dynamic applications
As accelerometer Least hysteresis and good setpoint accuracy
Magnetostrictive
As force sensors Compact force sensor with high resolution and bandwidth
Good for distributed and noncontact sensing applications
As torque sensor Accurate, high bandwidth, and noncontact sensor

Micro- and nano-sensors
Micro CCD image sensor Small size, full field image sensor
Fiberscope Small (0.2 mm diameter) field vision scope using SMA coil actuators
Micro-ultrasonic sensor Detects flaws in small pipes
Micro-tactile sensor Detects proximity between the end of catheter and blood vessels

SENSING
UNIT

CONTROLLED CONTROLLER
SYSTEM

ACTUATING
UNIT

\
FIGURE 16.1 A typical mechatronics system.

Sensors can also be classified as passive or active. In passive sensors, the power required to produce
the output is provided by the sensed physical phenomenon itself (such as a thermometer) whereas the
active sensors require external power source (such as a strain gage).
Furthermore, sensors are classified as analog or digital based on the type of output signal. Analog
sensors produce continuous signals that are proportional to the sensed parameter and typically require

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