Ultrasonic sensor specification and working principle

 Ultrasonic sensor

An ultrasonic sensor is an instrument that measures the distance to an object using ultrasonic sound waves. An ultrasonic sensor uses a transducer to send and receive ultrasonic pulses that relay back information about an object’s proximity. High-frequency sound waves reflect from boundaries to produce distinct echo patterns.

Ultrasonic sensors can measure the following parameters, without even getting in contact with the medium which is to be measured






What is an Ultrasonic Sensor ?

The Ultrasonic Sensor is a Transceiver Module (Transmitter + Receiver).

It transmits High Frequency Ultrasonic Waves of frequency greater than 20 KHz. Intercepts the waves reflected by an obstacle.

Electrical Signals, Ultrasonic Signals, Electrical Signals

Working Principle

When an electrical pulse of high voltage is applied to the ultrasonic transducer it vibrates across a specific spectrum of frequencies and generates a burst of sound waves. Whenever any obstacle comes ahead of the ultrasonic sensor the sound waves will reflect back in the form of echo and generates an electric pulse. It calculates the time taken between sending sound waves and receiving echo. The echo patterns will be compared with the patterns of sound waves to determine detected signal’s condition.

Construction of Ultrasonic 

Sensor Piezoelectric crystals are used for this conversion process. Piezoelectric crystals will oscillate at high frequencies when electric energy is applied to it. The reverse is also true. These piezoelectric crystals will generate electrical signals on receipt of ultrasound. These sensors are capable of sending ultrasound to an object and receive the echo developed by the object. The echo is converted into electrical energy for onward processing by the control circuit.

Interfacing & Features

description: ultrasonic transducer - receiver

max. input voltage: 20Vrms

operating temperature: -20 C to +85 C

range: 0.2 to 6m •nominal frequency: 40kHz

sensitivity: -67dB min.

sound pressure: 112dB min.

HC-SR04 Ultrasonic Sensor

 The HC-SR04 Ultrasonic sensor is a 4 pin module, whose pin names are Vcc, Trigger, Echo and Ground respectively. This sensor is a very popular sensor used in many applications where measuring distance or sensing objects are required. The module has two eyes like projects in the front which forms the Ultrasonic transmitter and Receiver.


The Vcc pin powers the sensor, typically with +5V


Trigger pin is an Input pin. This pin has to be kept high for 10µs to initialize measurement by sending Ultrasonic wave.


Echo pin is an Output pin. This pin goes high for a period of time which will be equal to the time taken for the Ultrasonic wave to return back to the sensor.


This pin is connected to the Ground of the system.

HC-SR04 Characteristics 

Supply voltage: 5V (DC).

Supply current: 15mA.

Modulation frequency: 40Hz.

Output: 0 – 5V (Output high when obstacle detected in range).

Beam Angle: Max 15 degree.

Theoretical measuring Distance: 2cm – 400cm.

Accuracy: 0.3cm.

HC-SR04 (Specifications)

It provides 2 - 400 cm non-contact measurement function.

Operating Voltage : 5V 

Working Frequency : 40 KHz 

Trigger Input Signal : 10μs TTL pulse

Advantges of Ultrasonic Sensor

Its small size makes it easy to integrate into projects.

Ultrasonics can easily integrate with any type of controller.

Its high frequency, sensitivity, and power make it easy to detect objects.

It have greater accuracy than many other methods at measuring thickness and depth of a parallel surface.

Ultrasonics are easy to use and not dangerous during operation.

An inexpensive option.

Application of Ultrasonic Sensor

  • Proximity Detection.
  • Liquid Level Sensing.
  • Obstacle Detection.
  • Ranging/Distance Measurement.
  • Anti Collision system.
  • Contouring or Profiling.
  • Presence Detection.
  • Product Counting and Sorting.
  • Anti Intrusion System.
  • Medical Imaging.


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