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How to Select the Ultrasonic Sensor

DFRobot May 04 2023 3791

With the continuous development of technology, ultrasonic sensing technology has been widely used in many fields. Ultrasonic sensors can measure distance, detect obstacles, and monitor liquid level by transmitting and receiving ultrasonic waves. However, when you need to choose an ultrasonic sensor that is suitable for your application, you need to consider many factors. This article will introduce how to choose an ultrasonic sensor, allowing you to select the sensor that best suits your needs and meets your requirements.

 How to Select the Ultrasonic Sensor

What is an ultrasonic sensor?

An ultrasonic sensor is an electronic device that uses sound waves to detect the distance or presence of objects. It sends out high-frequency sound waves and then listens for the echoes that bounce back. The time it takes for the sound waves to return helps determine the distance of the object. Ultrasonic sensors have two main components: the transmitter (which emits the sound using piezoelectric crystals) and the receiver (which encounters the sound after it has travelled to and from the target).

Ultrasonic Sensor: Working Principle

1.The working principle of an ultrasonic sensor involves the emission of high-frequency sound waves and the detection of their reflection.

2.The sensor sends out a sound wave at a frequency above the range of human hearing.

3.This sound wave travels through the air until it strikes an object.

4.When the sound wave hits an object, it is reflected back to the ultrasonic sensor.

5.The sensor then calculates the time it took for the sound wave to travel to the object and back and uses this to determine the distance to the object.

6.This distance is then converted into an electrical signal that can be used for a variety of applications, such as object detection, distance measurement, and level control.

Ultrasonic Sensor: Working Principle

Ultrasonic Sensor: Working Principle

Ultrasonic Sensor: Key Applications

  • Distance Measurement
  • Robotic Sensors
  • Smart cars – Tesla uses ultrasonic sensors as part of its Autopilot program!
  • Unmanned Aerial Vehicles (UAV) / Drones

  • Advantages of Ultrasonic Sensors

  • Not affected by object colour and transparency as it detects distance through sound waves
  • Performs well in low light conditions
  • Has a low power consumption rate
  • Offers various interface options for integration with microcontrollers or other systems

  • Factors to Consider When Selecting an Ultrasonic Sensor

    Choosing an ultrasonic sensor, the following factors should be considered:

    Measurement distance: When selecting an ultrasonic sensor, the appropriate model should be chosen based on the required measurement distance. Generally, the measurement distance of ultrasonic sensors ranges from a few centimeters to several meters.

    - If a sensor is too close to an object, it may not be able to measure the distance accurately. If a sensor is too far from an object, it may not detect the object at all. The sensor chosen for a distance measurement application must be properly rated for the expected minimum and maximum measurement distances.

    - Factors to consider when determining the useful operating range required (i.e., the material window) include: Material State: Liquids and solids behave differently when hit with soundwaves, which results in different interactions with ultrasonic sensors. Liquid measurements require a sensor with a range at least 25% greater than the expected maximum measurement, while dry measurements require a range at least 50% greater than the expected maximum.

    - Material size, shape, and orientation can also impact measurement accuracy, with large, flat water surfaces being easier to detect at a distance than curved or granular objects.

    Accuracy: The measurement accuracy of ultrasonic sensors is also a key factor to consider when choosing. Generally, the higher the measurement accuracy of an ultrasonic sensor, the higher its price.

    Operating frequency: The operating frequency of an ultrasonic sensor can also affect its performance. Generally, the higher the operating frequency of an ultrasonic sensor, the higher its measurement accuracy.

    Operating environment: The operating environment of an ultrasonic sensor is also a factor to consider when choosing. Some of the environmental factors to consider when choosing an ultrasonic sensor include: 

    - Temperature: Temperature, for instance, can impact the speed of sound, affecting the accuracy of distance measured by the sensor.

    - Weather: Ice, snow, dust, mud, and other environmental material buildup can block the sensor face, which can prevent the ultrasonic soundwaves from being transmitted or received. Additionally, the ingress of contaminants, such as water, can affect sensor function.

    - Pressure/Vacuum: Ultrasonic sensors are not designed for use in high-pressure or vacuum applications.

    - Ultrasonic noise can sometimes cause interference with measurement operations. Equipment, such as air nozzles, pneumatic valves, and ultrasonic welders, can generate this type of noise.

    Output signal: When choosing an ultrasonic sensor, its output signal type and method should also be considered so that it is compatible with the control system.

    Price: The price of an ultrasonic sensor is also a consideration, and the appropriate model should be selected based on actual needs and budget.

    Choose a suitable ultrasonic sensor based on the above reference factors by referring to the selection guide: DFRobot Ultrasonic Sensor Selection Guide.

    DFRobot Ultrasonic Sensor Selection Guide

    Disadvantages of Ultrasonic Sensors

  • Limited detection range: The monitoring distance of traditional ultrasonic sensors is limited by the distance between the transmitter and receiver, typically ranging from a few meters to tens of meters. This limits the sensor's application in certain situations.
  • Application limitations in special environments: The application of traditional ultrasonic sensors in special environments such as water is limited because the speed of sound in water is different from that in air, which can affect the sensor's accuracy.
  • Industrial application limitations: ultrasonic sensors often face challenges in industrial applications, including factors such as dust, vibrations, and temperature changes, which can affect sensor performance.
  • Low resolution and slow refresh rate, making it not suitable for detection of fast-moving targets
  • Unable to measure the distance of objects that have extreme textures/surfaces

  • Recommenced Ultrasonic Sensors

    The recommended ultrasonic sensor below can solve the problems mentioned above.

    Ultra Long Range Ultrasonic Distance Sensor - DFRobot URM12 ($189.00)

    The limited detection range of ultrasonic sensors can be solved by using multiple sensors and positioning them in such a way that they can cover a larger area. Another way is to use higher frequency ultrasound waves, which can increase the range of detection.

    This URM12 from DFRobot is a long range ultrasonic distance sensor designed for distance ranging or obstacle avoidance applications. The sensor offers up to 1500cm detection distance, 3Hz measuring frequency and 15° detection angle. It adopts RS485 communication interface and supports standard Modbus-RTU communication protocol, which is suitable for level measurement, robot obstacle avoidance and so on.


  • Power Supply: 9-24VDC
  • Rated Power: 4.8W
  • Operating Temperature Range: -10℃~+70℃
  • Effective Detection Range: 70cm~1500cm
  • Resolution: 1cm
  • Accuracy: 1%
  • IP Grade: IP65
  • Direction Angle: 15°±2°(-6dB)
  • Measuring Frequency: 3Hz Max
  • Communication Interface: RS485
  • Communication Protocol: Modbus-RTU

    Ultra Long Range Ultrasonic Distance Sensor - DFRobot URM12

    Ultra Long Range Ultrasonic Distance Sensor - DFRobot URM12

    Waterproof Ultrasonic Sensor - DFRobot A02YYUW ($15.90)

    The emergence of waterproof ultrasonic sensors is mainly to meet the needs of special environments, such as measuring and detecting underwater. Waterproof ultrasonic sensors can achieve high waterproof rating and can measure and detect in liquids, with good stability and reliability.

    DFRobot A02YYUW is an easy-to-use commercial-grade ultrasonic sensor module of high performance and reliability, featuring much smaller blind zone, wider sensing angle and a certain penetration power(smog, dust) compared with other similar sensors. It adopts closed separated probe, waterproof and dustproof, which could be well suitable for harsh and moist measuring environment. All the signal processing units are integrated inside the module, so users can directly obtain the distance value through Asynchronous Serial Interface. With 9600bit/s band rate, the sensor can easily communicate with upper-host or other MCU, which greatly shortens the developing cycle for users.


  • Accuracy: ±1cm
  • Operating Voltage: 3.3~5V
  • Average Current: <8mA
  • Blind Zone Distance: 3cm
  • Detecting Range(Flat object): 3-450cm
  • Output: URAT
  • Response Time:100ms
  • Operating Temperature: -15~60℃
  • Storage Temperature: -25~80℃
  • Reference Angle: 60º
  • Waterproof Grade: IP67
  • Waterproof Ultrasonic Sensor - DFRobot A02YYUW

    Waterproof Ultrasonic Sensor - DFRobot A02YYUW

    Industrial Ultrasonic Distance Sensor with 1mm Accuracy - DFRobot URM14 ($99.00)

    The emergence of industrial ultrasound sensors aims to meet the needs of non-contact measurement in industrial production. Traditional physical contact measurement methods are easily affected by environmental interference. However, industrial ultrasound sensors can quickly and accurately perform measurement, improve the efficiency and accuracy of industrial automation production. At the same time, industrial ultrasound sensors also have characteristics such as waterproof, high temperature resistance, and corrosion resistance. They can adapt to harsh industrial environments and have a long service life.

    DFRobot URM14 200KHz ultrasonic distance sensor with 1mm accuracy(10~150cm, RS485) is a high-frequency precision ultrasonic sensor for industrial use. The sensor measurement and signal processing unit is completely encapsulated in an M18 metal shell and its tail is designed with an aviation connector plug. The sensor uses the RS485 interface that follows the standard Modbus-RTU communication protocol, which assures its compatibility with PLC industrial personal computer. Furthermore, the adoption of higher ultrasonic acoustic frequency and more precision signal processing circuit gives this URM14 sensor mm-grade accuracy and up to1.5m reliable measuring range. The only 12° measuring angle makes the sensor able to present the directional measurement characteristic similar to laser ranging sensors.

    Industrial Ultrasonic Distance Sensor - DFRobot URM14

    Industrial Ultrasonic Distance Sensor - DFRobot URM14


  • Operating Voltage: DC 7-15V
  • Max Instantaneous Current: 350mA
  • Effective Measuring Range: 100-1500mm
  • Distance Resolution: 0.1mm
  • Measuring Accuracy: 1mm
  • Distance Error: ±0.1%
  • Temperature Resolution: 0.1℃
  • Measuring Frequency: 30HZ
  • Operating Temperature: -20℃~+80℃
  • Sensor Acoustic Frequency: 200KHz±4%

  • Figure: Assembly Line Product Position/ Height Calibration


    When selecting an ultrasonic sensor, it’s important to consider the range and accuracy you need for your specific application. Factors such as the frequency, beam angle, and power consumption should also be taken into consideration when making your selection. Additionally, it’s important to choose a sensor that is compatible with your existing equipment and that is durable enough to withstand the environment in which it will be used. By taking these factors into account and carefully evaluating your options, you can choose the best ultrasonic sensor for your specific needs and ensure accurate and reliable measurements.