58
F. Firouzi et al.
Table 2.1 Types of proximity sensors
Sensor technology
Range of use Common use
Inductive sensor
4 mm–40 mm Close-range detection of ferrous metals such as copper,
aluminum, iron, etc.
Capacitive sensor
3 mm–60 mm Close-range detection of nonferrous materials such as
liquid, plastic, or wood
Photoelectric sensor 1 mm–60 mm Long-range military target recognition
Ultrasonic sensor
3 mm–30 mm Long-range military target detection with difficulties
such as many colors or inconsistent service
the state of free fall. This feature is included in many computer hard drives.
If the device senses that the hard drive is falling, the drive automatically turns
off to protect against losing data. When choosing an accelerometer, the key
characteristic for consideration is number of axes measured. It is actually very
simple: There are three possible axes (x, y, z). Of the three, how many can the
accelerometer measure? A device that can measure all three axes is usually the
best option. These are widely available and are usually no more expensive than
accelerometers that measure only one or two axes.
• Gyroscope – Measures angular velocity (i.e., how fast an object spins around an
axis). When measuring the orientation of a moving object, an accelerometer may
not be able to provide orientation-specific information. However, gyroscopes
are not affected by gravity and work as a complementary partner with the
accelerometer. Angular velocity is measured in units of rotation per minute
(RPM) or in degrees per second. The axes of rotation (x, y, and z) are also referred
to as roll, pitch, and yaw. Gyroscopes have proven useful in navigating space,
controlling missiles, providing underwater navigation, and guiding aircraft.
Currently, gyroscopes and accelerometers are being used together in vehicle
navigation and motion-capture applications. In general, gyroscopes are not as
advanced as accelerometers, and less expensive three-axis gyroscopes have
only recently become available on the market, with most commonly available
gyroscopes still measuring only one or two axes. When purchasing a gyroscope,
it is important to understand which axes are measurable. For example, one twoaxis gyroscope could measure pitch and roll, while another two-axis gyroscope
measures pitch and yaw.
• Proximity and Displacement Sensors – Use electromagnetic fields, sounds, or
light to detect the absence or presence of objects. The different types of proximity
sensors are each useful in specific environments or scenarios (see Table 2.1)
[3]:
– Inductive Sensors – Detect ferrous material at close range
– Capacitive Sensors – Detect nonferrous material at close range
– Photoelectric Sensors – Detect long-range targets
– Ultrasonic Sensors – Detect long-range targets with difficult surfaces
F. Firouzi et al.
Table 2.1 Types of proximity sensors
Sensor technology
Range of use Common use
Inductive sensor
4 mm–40 mm Close-range detection of ferrous metals such as copper,
aluminum, iron, etc.
Capacitive sensor
3 mm–60 mm Close-range detection of nonferrous materials such as
liquid, plastic, or wood
Photoelectric sensor 1 mm–60 mm Long-range military target recognition
Ultrasonic sensor
3 mm–30 mm Long-range military target detection with difficulties
such as many colors or inconsistent service
the state of free fall. This feature is included in many computer hard drives.
If the device senses that the hard drive is falling, the drive automatically turns
off to protect against losing data. When choosing an accelerometer, the key
characteristic for consideration is number of axes measured. It is actually very
simple: There are three possible axes (x, y, z). Of the three, how many can the
accelerometer measure? A device that can measure all three axes is usually the
best option. These are widely available and are usually no more expensive than
accelerometers that measure only one or two axes.
• Gyroscope – Measures angular velocity (i.e., how fast an object spins around an
axis). When measuring the orientation of a moving object, an accelerometer may
not be able to provide orientation-specific information. However, gyroscopes
are not affected by gravity and work as a complementary partner with the
accelerometer. Angular velocity is measured in units of rotation per minute
(RPM) or in degrees per second. The axes of rotation (x, y, and z) are also referred
to as roll, pitch, and yaw. Gyroscopes have proven useful in navigating space,
controlling missiles, providing underwater navigation, and guiding aircraft.
Currently, gyroscopes and accelerometers are being used together in vehicle
navigation and motion-capture applications. In general, gyroscopes are not as
advanced as accelerometers, and less expensive three-axis gyroscopes have
only recently become available on the market, with most commonly available
gyroscopes still measuring only one or two axes. When purchasing a gyroscope,
it is important to understand which axes are measurable. For example, one twoaxis gyroscope could measure pitch and roll, while another two-axis gyroscope
measures pitch and yaw.
• Proximity and Displacement Sensors – Use electromagnetic fields, sounds, or
light to detect the absence or presence of objects. The different types of proximity
sensors are each useful in specific environments or scenarios (see Table 2.1)
[3]:
– Inductive Sensors – Detect ferrous material at close range
– Capacitive Sensors – Detect nonferrous material at close range
– Photoelectric Sensors – Detect long-range targets
– Ultrasonic Sensors – Detect long-range targets with difficult surfaces