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Distance Sensors: A Comprehensive Guide

We have many distance sensors such as IR, Laser, ultrasonic, LED time-of-flight (TOF) sensors, etc. Therefore, selecting one for your project can be challenging.

Today’s article looks at various distance sensors, their applications, advantages, and disadvantages. Let’s get going.

What is a Distance Sensor?

A Mounted Infrared Sensor

Fig 1: A Mounted Infrared Sensor

A distance sensor is an electronic device that measures the distance between two objects without physical contact

Therefore, it offers a fast and accurate measurement, positioning, and range of objects.

How do Distance Sensors Work?

Working of an Ultrasonic Sensor

Fig 2: Working of an Ultrasonic Sensor

All distance sensors have the same principle of operation regardless of the technology involved. 

If you want to measure the distance between two points, here’s how your distance sensor works:

  • First, a distance sensor transmitter sends a signal towards the object.
  • Consequently, the signal is reflected/ bounces back upon hitting the object.
  • The sensor’s receiver gets the reflected signal.
  • It then calculates the delay from when the call was transmitted and received. 
  • Finally, it uses the delay to calculate the distance between itself and the object.

The delay measured can be in the following forms:

  • Change of phase of the returning signal
  • Returning signal’s intensity
  • Finally, the time delay between transmission and reception of the signal

What Are the Types of Distance Sensors?

Ultrasonic Distance Sensor

Close-Up of a Drone Helicopter

Fig 3: Close-Up of a Drone Helicopter

The ultrasonic distance sensor relies on high-frequency sonar/ sound waves to gauge the distance to an object. 

Here’s how it works:

  • The ultrasonic sensor sends high-frequency sound waves towards an object/ obstacle.
  • At the same time, a timer is started, and like an echo, the waves bounce back to the sensor’s receiver.
  • Consequently, the timer stops immediately after the sensor receives the reflected signal.
  • Finally, it calculates the distance between the objects by contrasting the time of signal travel against the speed of sound.

Infrared Distance Sensors

This sensor module uses the principle of triangulation or measuring the distance between two objects using the angle of reflection. 

Here’s how it works:

  • It emits an infrared light signal through an LED emitter and receives the reflected signal at its position-sensitive photodetector (PSD) lens. 
  • Finally, the PSD sensor determines the distance of the reflective object using the angle of reflection.

Laser Distance Sensors (LiDAR)

Autonomous Self-Driving Electric Car Showing Lidar and Safety Sensors Use

Fig 4: Autonomous Self-Driving Electric Car Showing Lidar and Safety Sensors Use

Light Detection and Ranging (LiDAR) is a laser distance sensor that works in the following way:

First, the transmitter emits laser light toward the object/ obstacle. The object reflects the signal/ pulse towards the LiDAR’s receiver. 

And finally, the sensor calculates the distance between the two objects by using the relationship between the speed of light and time.

LED Time-Of-Flight Distance Sensors

Time-of-flight (TOF) sensors measure distances by determining the time taken by a wave to travel from the transmitter and back. 

Consequently, it uses the relation between the light speed in the air and the signal’s flight time to get the distance.

Therefore, it can produce 3D X, Y, and Z images using data from a single snapshot. 

Advantages: High accuracy、 Can identify large objects、Supports 3D imaging

Disadvantages: Expensive、Poor Z-depth resolution

Applications: Robotics and drones、Machine vision、Industrial applications、Counting

Sonar Distance Sensor

Have the same working principle as the ultrasonic sensors but excel more underwater. For your information, there are two types of sonar sensors; passive and active. 

  • First, active sonar sensors emit a signal and determine distance upon receiving a reflected signal. 
  • On the other hand, passive sonars lack a transmitter and only receive a signal from another object. 

Applications: Loop control、People detection and detection of submarines、Stack height control

Short-range Distance Sensor

The Robot Vacuum Cleaner Vacuums the Floor in the Apartment

Fig 5: The Robot Vacuum Cleaner Vacuums the Floor in the Apartment

Short-range distance sensors measure distances between close objects. They are high-resolution sensors and can have a minimum range from 1 mm to 2,000 mm or more.

Advantages: Low operating voltage consumption, 、Low cost, and accurate

Applications: People detection and precision range finding、Controlling lights、Robotic vacuum cleaners

Long-range Distance Sensor

Long-range sensors use pulsed time-of-flight principles to measure distances of up to 300 meters. 

Advantages: Has a longer reach, 、Highly versatile, and sampling rates

Disadvantages: Expensive

Applications: Load confirmation and lumber positioning, Crane monitoring, Measuring fill levels, velocity, and altitudes

Comparing the Distance Sensors

Suitability for Long Range Sensing

The LiDAR and TOF sensors have suitability for long-range sensing, whereas the Ultrasonic and IR sensors don’t.

High Reading Frequency

The LiDAR and TOF sensors have a high reading frequency. In contrast, the ultrasonic and IR sensors don’t.


Ultrasonic and IR sensors are cheap compared to LiDAR and TOF. Furthermore, LiDAR is the most expensive of the four distance sensors.

Suitability to Use for Complex Objects

The LiDAR, IR, and TOF sensors have excellent suitability to use for complex objects. However, you can only use ultrasonic sensors for simple things.

Sensitive to External Conditions

The LiDAR, IR, and TOF sensors are sensitive to external conditions, unlike the ultrasonic sensors, which aren’t.

3D Imaging Compatible

The LiDAR and TOF sensors are 3D imaging compatible, whereas the ultrasonic and IR sensors aren’t.


Generally, distance sensors have a ton of applications in our everyday lives. If you plan to use one in your project, consider cost, size, suitability, and durability.

Finally, if you have any gray area that needs clarification, please contact us. We’ll get back to you at the soonest time possible.

Hommer Zhao
Hi, I am Hommer, the founder of WellPCB. So far, we have more than 4,000 customers worldwide. If you have any questions, you can feel free to contact me. I really appreciate any help you can provide.