Ultrasonic Based Distance Measurement System

Main aim of the Ultrasonic Based Distance Measurement System is to measure the distance using the ultrasonic waves. The human ear is insensitive to ultrasonic waves because audible perception range of ear is from 20 Hz to 20 kHz only.

Advantages of Ultrasonic Based Distance Measurement System:

  1. In industries, it can be used as range meter and proximity detector.
  2. It is also useful in vehicle parking assistance system.

The pulse echo method and phase measurement method can be used to measure the distance. In the pulse echo method, a continuous signal in the transmission frequency range of transducers is measured by the measurement unit. An obstacle will reflects this signal and another transducer will receive that signal. In this method, the distance between the system and the obstacle is corresponding to the time delay of the transmitted and the received signal. The wave and pulse echo technique are used to measure distance using the ultrasonic signal in air.

In the pulse echo method, the transmission medium is used to send a burst of pulses and an object which is far away from that transmission medium will reflect that pulses. The distance of an object which reflects pulse is directly proportional to the time taken for pulse transfer between the transmitter and the receiver. The device needs to go to the target for reflecting the pulse back to itself during contactless measurement of distance. The amplitude of the received signal is significantly attenuated. This system can be used in measuring the distance between the transmitter and target. The direction of propagation of the pulses plays an important role in the orientation of the target.

The pulse echo or time-of-flight methods are used for measuring the distance in air medium to limit its distance range.

Design procedure:

Two divisions of the circuit are as follows:

  1. Digital section- includes a micro controller and LCD display unit with 5volt power supply.

2. Analog section – It has two subdivisions they are:

(a) Transmitting side – include an Ultrasonic transducers, which gain amplifier using uA741 CD4066 CMOS analog switch.

(b) Receiving side – includes a TL084 comparator, which gain amplifier, voltage limiter.

(c) Power supply range between+15V and -15V.

The distance between the transmitter and the object is measured using the time of flight. The burst of pulses is sent by the transmitter and the reflected echo is detected by the receiver. Micro controller is used to measure the time delay during transmitting and receiving the pulses. The formula used to calculate the distance between the transmitter and the target is given below:

Distance = Velocity X Elapsed time


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