Page 137 - Sensors and Control Systems in Manufacturing

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2.10 Understanding Microwave Sensing Applications
Microwave sensors are valuable tools in the industrial environment
for measuring motion, velocity, direction of movement, and range.
They are rugged devices capable of operating in hostile environ-
ments, and are intrinsically safe, since they have no moving parts and
require low power. They will not cause any harm to operators and
will function effectively in explosive environments. They can suc-
cessfully measure large military and industrial objects over large dis-
tances and can provide a great deal of information about these objects,
as observed during the Persian Gulf War in 1991, Iraq war in 2003,
and current Afghanistan war on terror.
Microwave technology has long been an effective method of mea-
suring the parameters of motion and presence. Applications range
from simple intrusion alarms that merely indicate an object has entered
its field of view to complex military radar systems that define the exis-
tence, location, and direction of motion in military maneuvers.
Microwave sensing technology can be classified into five categories:

• Motion sensing. Sensing a moving object in a defined domain—
for example, detecting an intruder in a prohibited area.
• Presence sensing. Sensing that an object exists in a defined
domain at a given time. This concept is vital in industrial
control systems where the arrival of an object may not be
noticed.
• Velocity sensing. Sensing the linear speed of an object in a
specified direction. This concept is used by police to detect
speeding cars.
• Direction-of-motion sensing. Determining whether a target is
moving away from or toward the microwave sensor device.
This concept is particularly important for manufacturers of
automated guided vehicle systems for obstacle avoidance. It
is also used to detect whether objects or personnel are
approaching or departing from automatic doors.
• Range sensing. Measuring the distance from the sensor to an
object of interest. Applications include sensing the level of oil
or chemical solutions in tanks and containers.

2.10.1 Characteristics of Microwave Sensors
Microwave sensors’ general characteristics important in industrial
and commercial applications are:

• No contact. Microwave sensors operate without actually
contacting the object. This is particularly important if the object
is in a hostile environment or sensitive to wear. They can