What is Ultrasonic Sensor: Working Principle & Applications

What is Ultrasonic Sensor


Are you looking for an accurate, reliable, and cost-effective way to measure the distance, level, or presence of an object?  If the answer is Yes! Consider an ultrasonic sensor. This blog post covers what it is, the principle of working, how it is used and its applications Ready to learn more?  If you want to learn more about these amazing devices, then keep reading!

What is Ultrasonic Sensor?

What is Ultrasonic Sensor?

The Ultrasonic Sensor is an electronic device that calculates distance by emitting sound waves and collecting their echoes.

It can measure objects from up to 4.5 meters away, which makes it a versatile instrument for correctly measuring both short and long distances without making contact with the target object, which is critical in many applications such as obstacle avoidance systems in robotics or autonomous cars.

The sensor features adjustable pulse widths, allowing for higher resolution measurements when set at lower levels though this comes at the cost of range accuracy diminishing as a result, however, due to its affordability compared to other forms of distance sensing technologies makes it incredibly suitable where budget constraints are paramount factor within projects evaluating solutions using ultrasonic technology.


What is Ultrasonic Sensor


Ultrasonic sensors are used as proximity sensors. They are used in parking technologies and anti-collision safety systems. Ultrasonic sensors are also employed in automated obstacle detection systems and factory engineering.

Compared to infrared (IR) sensors in proximity sensing applications, ultrasonic sensors are less susceptible to interference from smoke, gases, and other airborne particles (although the physical component is subject to variables such as heat).

Ultrasonic sensors function like multitasking experts! They are not just used to measure liquid levels in containers, they also enable doctors to view inside organs, identify cancer, and monitor babies in the womb.

Working Principle of Ultrasonic Sensor?

An ultrasonic sensor is a type of electronic sensor that uses ultrasonic waves to determine the distance between two objects and converts the reflected sound into electrical signals.

The working principle of an ultrasonic sensor is to measure distance using ultrasound, which travels faster than sound that is audible. This sensor consists of two major components a transmitter that generates sound waves via a piezoelectric crystal and a receiver that detects the reflected ultrasonic waves.

Working Principle of Ultrasonic Sensor


While some sensors have separate sound emitters and receivers, the two functions can be combined into a single device by using an ultrasonic element that alternates between sending and receiving signals in a continuous loop.

The transmitter of the module transmits an ultrasonic sound. This sound will be reflected if an object is present in front of the ultrasonic sensor. The reflected sound is received by the receiver present in the same module.

An ultrasonic signal is propagated by a wave at an angle of 30°. The above-depicted Figure illustrates how the ultrasonic signal propagates from the transmitter. Measuring angles should be at least 15° for maximum accuracy.

In this case, external objects that fall under this measurement angle interfere with determining the distance to the desired object.

The distance is calculated by measuring the ultrasonic sound's travel time and speed.

Distance = Time x Speed of sound / 2


Example of How Ultrasonic Sensor Works:

Assume you are working on a project to design a parking system for a city. You choose to include sensors in the design to ensure car detection while parked.

Ultrasonic sensors are carefully installed at each parking spot in the lot. When cars enter the parking lot, they pass by rows of ultrasonic sensors.

When a vehicle passes by an ultrasonic sensor it emits a frequency sound wave, in response. This wave reflects off the car. Returns as an echo to the sensors transducer, which acts as both sender and receiver.

The sensor then calculates the time taken for the wave to travel back and forth from the vehicle. Given that the sound's velocity is known, it can accurately determine the distance, between itself and the car.

Reflection of the sensing sound varies with configuration, for example


How ultrasonic sensor works


(A) Flat objects: liquid, box, plastic sheet,

(B) Columnar objects: can, bottle, the human body,

(C) Granular objects: ores, rock, coal, coke, plastic pellet,

To generate the ultrasonic sound, need to trigger the trigger pin as high for a minimum of 10us. Then the module will start sending 8 sonic burst ultrasounds from the module at 40 Khz.

It will receive by the receiver called Echo pin and it will calculate the output time to measure the distance.



To prevent mutual interference between Ultrasonic Sensors, the synchronous operation can be used by emitting the ultrasonic waves from each Sensor simultaneously.



  • Supply voltage +5 V;
  • Consumption in silent mode 2 mA;
  • Consumption at work of 15 mA;
  • Measurement range - 2 to 400 cm;
  • Effective measuring angle 15°;
  • The dimensions are 45Ă—20Ă—15 mm.

Read our blog on how to connect ultrasonic sensor to Raspberry Pi where we discuss how ultrasonic Sensors Work, how to calculate the distance between the ultrasonic sensor and the object, and the complete process of Interfacing HC-SR04 with Raspberry Pi.

How are Ultrasonic Sensors used?

With microcontroller platforms like the Raspberry Pi, ARM, PIC, Arduino, Beagle Board, and many more, our ultrasonic proximity level and distance sensors are often employed.

Ultrasonic sensors will send sound waves in the direction of the target and calculate its distance by timing how long it takes for the waves to bounce back to the sensor. In addition, to collision avoidance systems also employ ultrasonic sensors.

Here, implemented ultrasonic sensor with Arduino. Before interfacing let us see the pinout of the ultrasonic sensor,

Ultrasonic Sensor Pin Diagram

Four pins in the ultrasonic sensor


power supply +5 V


Common ground

Trigger pin

To start the sensor

Eco pin

Receive the signal

Use multiple sensors to avoid interference

When using multiple sensors in an application, it is important to connect them in a way that avoids problems such as crosstalk and other interference. 

It is important to keep the front of the ultrasonic transducer clear to avoid interference with the ultrasonic signal from the sensor.

Check out our complete guide on Arduino Interfacing with Ultrasonic Sensor

How to Connect HC-SR04 Ultrasonic Sensor to Arduino:

Before going to the steps you need to ensure that you have the following Hardware.

  1. Arduino Board (You can use any Arduino Board)
  2. HC-SR04 Ultrasonic sensor
  3. Jumper cables

Steps for Arduino Interfacing with Ultrasonic Sensor:

Step 1: Make all the connections properly as per the diagram shown in the image below.

How to Connect HC-SR04 Ultrasonic Sensor to Arduino

Step 2: Now open Arduino IDE or you can Install Arduino Sketch coding software on your desktop and type the below code.

#define echoPin 6

#define trigPin 7


long duration;

int distance;


void setup()


  pinMode(trigPin, OUTPUT);

  pinMode(echoPin, INPUT);



void loop()


  digitalWrite(trigPin, LOW);


  digitalWrite(trigPin, HIGH);


  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH);

  distance = duration * 0.034 / 2;

  Serial.print("Distance: ");


  Serial.println(" cm");


Step 3: Now connect your Arduino Board to the PC by using an Arduino USB cable.

Step 4: Now select the correct board by simply going to Tools >> Boards >> Arduino AVR Boards >> Arduino UNO.

Then select the correct port by going to Tools >> Ports >> Port where the Arduino board is connected. You can make it sure by check in the device manager. 

steps to interface ultrasonic sensore with arduino

Step 5: After selecting the correct port and board just click on the upload icon.

Now you are ready to see the distance measurement by ultrasonic sensor on serial monitor.

Advantages of Ultrasonic Sensors

  1. Ultrasonic sensors are a fantastic tool for measuring the distance, speed, and position of things. They provide greater accuracy than traditional technology such as lasers or infrared sensors.
  2. The ultrasonic wave is generated through a transducer that sends out high-frequency sound waves which travel faster than the speed of light due to their higher frequency range (ultrasonics is in the kilohertz range).
  3. These sensors enable manufacturers and engineers for detailed detection over wide ranges with minimal complexity involved when setting up certain systems; they can even detect objects at distances greater than 200m away accurately!
  4. Ultrasonic sensors also do not rely on visible light like other types of technology so they can be used indoors/outdoors without worrying about environmental conditions affecting performance levels - this makes them ideal for use in dark areas or lowlight situations where visibility would otherwise be compromised by regular sensing techniques
  5. These devices have self-diagnostics capabilities allowing users quick access to system status by checking errors & fault codes and reading back calibration parameters, thus providing easy maintenance routines.
  6. With no external power source needed, these types of tools operate more reliably with less downtime thus leading to improved productivity levels across applications relying heavily on its usage ranging from robotics automation industrial monitoring security surveillance activities etc,.

Applications of Ultrasonic Sensor

Ultrasonic Anemometers:

In weather stations, ultrasonic anemometers provide accurate measurements of wind direction and speed. While 2D anemometers deal with horizontal winds, 3D anemometers involve a vertical component.

These advanced equipment track differences in temperature as well as changes in ultrasonic velocity, giving weather forecasters an in-depth understanding of the weather.

Tide Gauge:

Using ultrasonic sensors to quickly detect water levels, the tide gauge is a crucial tool for monitoring sea levels and identifying a variety of coastal events, such as waves, water surges, tsunamis, and floods.

Sometimes these measures are incorporated into online databases, which allows timely notifications for potential sea dangers and simplifies record administration.

Tank level:

Measuring liquid levels in tanks is similar to using a level meter. However, in this scenario, the fluid could be freshwater, corrosive chemicals, or flammable liquids.

Ultrasonic sensors, unlike optical sensors and float switches, do not come into contact with liquids, hence they are less prone to corrosion.

Web-guiding systems:

Web-guiding systems ensure accurate material placement. If the material is mismatched, the system will mechanically move it back into the machine path.

Ultrasonic sensors are well suited for web guiding, as the process requires non-contact, fast and efficient functionality.

UAV navigation:

Unmanned Aerial Vehicles (UAVs) (or drones) typically use ultrasonic sensors to monitor objects in their flight path and the UAV's distance from the ground.

By automatically detecting safe distances, aircraft can avoid collisions. In addition, since the flight path changes in an instant, drone collision can be prevented by detecting the distance with ultrasonic waves.

Limitations of Ultrasonic Sensors

  1. Ultrasonic sensors have a limited range which makes them less effective when larger distances need to be covered or detected.
  2. They are prone to interference from other sources and can provide false readings due to these interferences, including reflections off of non-metallic objects that may not be correctly identified by the sensor’s recognition capabilities.
  3. Response times for ultrasonic sensing technology is relatively slow in comparison with some other types of distance measurement equipment such as infrared devices meaning they take longer periods of time before an accurate reading is provided back on screen, making it inconvenient where fast responses are needed immediately upon detection.
  4. High-density materials, extreme temperatures and small target surfaces are also unable to detect properly using ultra-sonic sensors since their performance gradually reduces under those conditions leading them to underestimate the actual values being measured within their vicinity environment.


This blog post has informed us about the working principle of ultrasonic sensors, which are a very flexible technology with a wide range of real-world uses. Gaining knowledge about the fundamentals and operations of these sensors will enable you to fully understand the variety of advantages they provide, ranging from automation and security to scientific and medical research.

You may open up a whole new world of possibilities and advance your projects by utilizing the power of ultrasonic sensors. Why not learn more about the exciting field of ultrasonic sensors and see how they might improve your work right now?


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Frequently Asked Questions

1. What is an ultrasonic sensor used for?

An ultrasonic sensor is a device that uses sound waves to detect the presence and proximity of objects. It sends out high-frequency sound waves that bounce off objects and then measures the time it takes for the sound waves to return. Ultrasonic sensors are commonly used in applications such as parking assist systems, robotics, and distance-measuring devices.

2. What are the advantages of ultrasonic sensor?

The ultrasonic sensors are just absolutely amazing! They have so many advantages, it's almost hard to keep track of them all! For one thing, they can detect the distance and position of objects with incredible accuracy, even in really tough environments like low-light or dusty ones. And get this, they don't even need to touch the object they're sensing, making them super easy to use in all kinds of different applications, from industrial automation to car safety systems.

3. What does an ultrasonic sensor do?

An ultrasonic sensor is an innovative technology that uses sound waves to detect motion and measure distances. It works by sending out high-frequency acoustic pulses, which are reflected by objects in the environment. The returning echoes are detected and measured accurately for a range of applications such as obstacle avoidance, flow measurement or security detection systems. As this method does not rely on light being visible between points, it can be used in dark environments making it extremely versatile and ideal for use indoors or outdoors where traditional technologies fail due to environmental conditions. By utilizing advanced parameters tuning algorithms combined with relevant data processing techniques we ensure excellent performance levels over time even under extreme operating conditions ensuring reliable results every time!

4. What is the basic principle of ultrasonic sensor?

Ultrasonic sensors are devices which measure the distance of an object by using sound waves. Ultrasonic waves travel in air at a known speed and when they hit a solid surface, part of them is reflected back to their source. The time difference between sending and receiving these ultrasonic pulses allows us to accurately calculate the distance from our position up to 5 meters away with resolutions within millimetres. This sensor technology can be found most commonly used in automotive park assist systems, burglar alarm detectors or presence sensing for automated machine operations. 

5. Is ultrasonic sensor analog or digital?

Ultrasonic sensors are an important part of many modern applications, so it's essential to know whether they're analog or digital. Ultrasonic sensors use sound waves that travel through air and measure the time needed for them to reach a target object and return back. They then convert this data into electrical signals which can be either analog or digital. Analog ultrasonic sensors generate continuous voltage output as measured by the echo ranging interval whereas digital ultrasonic sensors provide discrete pulse-width modulation (PWM) outputs when triggered. This makes them ideal for measuring distances precisely with no direct contact between transmitter/receiver units - great in robotics applications! Ultimately, your choice will depend on what type of input you need from your application: logic level values versus raw voltages – make sure you choose carefully depending on your needs!

6. How do I connect ultrasonic sensor to Raspberry Pi 4?

Connecting an ultrasonic sensor to a raspberry pi 4 4gb is fairly straightforward. The first step is to identify the pins on your specific device, and then connect each pin directly onto the corresponding GPIO port of your raspberry pi 4 4gb. Once these are secure you can install any necessary software packages such as Python before proceeding with programming the connection between your sensor and raspberry pi 4 4gb. After verifying correct communication just run through some basic tests ensuring that all data collected from various readings is being sent accurately back into the system for further analysis or decision making tasks either by yourself or other programs running alongside it in parallel operations . With simple applications like this you should be able to easily integrate numerous components into one physical platform allowing for much more sophisticated control projects while still remaining compact thanks largely due its small size coupled with greater processing power than what was previously available form earlier models like earlier generation Pis 3 B+.

7. What is the difference between sonar and Ultrasonic sensors?

Main five differences between sonar and ultrasonic sensors:

  • Sonar sensors use a wide range of sonic frequencies. While Ultrasonic sensors specifically operate at frequencies greater than 20kHz.
  • Sonar sensors are mainly used underwater. While Ultrasonic sensors find applications in automotive, robotics, and industry.
  • Sonar sensors emit sound pulses and listen for echoes. While Ultrasonic sensors send bursts of ultrasonic pulses and measure echo return time.
  • Sonar sensors offer a longer range but lower resolution. While Ultrasonic sensors provide better resolution at shorter ranges.
  • Ultrasonic sensors are unaffected by object color and less affected by airborne particles.

8. Why is it called an Ultrasonic sensor?

It's named an ultrasonic sensor because it uses ultrasonic waves to measure distance. Ultrasonic waves are sound frequencies beyond what humans can hear, usually above 20 kilohertz (kHz). 

9. What is the distance range of the ultrasonic sensor?

The ultrasonic sensor, like the HC-SR04 model, can measure distances ranging from 2 centimeters to 400 centimeters, about 1 inch to 13 feet within a 30-degree cone. It provides precise measurements to the nearest 0.3 centimeters.

10. What is the frequency of the Ultrasonic sensor?

For air-based applications, ultrasonic sensors commonly use frequencies between 30 and 500 kilohertz (kHz). Higher frequencies work better over shorter distances, whereas lower frequencies, between 30 and 80 kHz, are better for long-range sensing. The frequency selection impacts the sensor's performance at various ranges, absorption occurs more quickly at higher frequencies.

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