Week 10 :Research The UltraSonic Sensor

                          Parallax's PING)))™ ultrasonic sensor provides a very low-cost and easy method of distance measurement. This sensor is perfect for any number of applications that require you to perform measurements between moving or stationary objects. Naturally, robotics applications are very popular but you'll also find this product to be useful in security systems or as an infrared replacement if so desired.

This measures distance using sonar; an ultrasonic (well above human hearing) pulse is transmitted from the unit and distance-to-target is determined by measuring the time required for the echo return. Output from the PING))) sensor is a variable-width pulse that corresponds to the distance to the target.
PING)))™ Sensor Features:

• The PING))) has only has 3 connections, which include Vdd, Vss, and 1 I/O pin.
• The 3-pin header makes it easy to connect using a servo extension cable, no soldering required.
• Several sample codes are available using the Ping))) sensor.

List of technical specifications:

• Range - 2cm to 3m (~.75" to 10')
• Supply Voltage: 5V +/-10% (Absolute: Minimum 4.5V, Maximum 6V)
• Supply Current: 30 mA typ; 35 mA max
• 3-pin interface (power, ground, signal)
• 20 mA power consumption
• Narrow acceptance angle
• Simple pulse in / pulse out communication
• Indicator LED shows measurement in progress
• Input Trigger - positive TTL pulse, 2 µs min, 5 µs typ.
• Echo Pulse - positive TTL pulse, 115 µs to 18.5 ms
• Echo Hold-off - 750 µs from fall of Trigger pulse
• Burst Frequency - 40 kHz for 200 µs
• Size - 22 mm H x 46 mm W x 16 mm D (0.85 in x 1.8 in x 0.6 in)

Ultrasonic sensors (also known as transducers when they both send and receive) work on a principle similar to radar or sonar which evaluate attributes of a target by interpreting the echoes from radio or sound waves respectively. Ultrasonic sensors generate high frequency sound waves and evaluate the echo which is received back by the sensor. Sensors calculate the time interval between sending the signal and receiving the echo to determine the distance to an object.

This technology can be used for measuring: wind speed and direction (anemometer), fullness of a tank, and speed through air or water. For measuring speed or direction a device uses multiple detectors and calculates the speed from the relative distances to particulates in the air or water. To measure the amount of liquid in a tank, the sensor measures the distance to the surface of the fluid. Further applications include: humidifiers, sonar, medical ultrasonography, burglar alarms, and non-destructive testing. Systems typically use a transducer which generates sound waves in the ultrasonic range, above 20,000 hertz, by turning electrical energy into sound, then upon receiving the echo turn the sound waves into electrical energy which can be measured and displayed. The technology is limited by the shapes of surfaces and the density or consistency of the material. For example foam on the surface of a fluid in a tank could distort a reading.