What is the Difference Between PIR Sensor and Ultrasonic Sensor

The key difference between PIR sensor and ultrasonic sensor is that a PIR sensor can detect the presence of an object by sensing the difference between heat emitted by the movement of the object and the heat of the background, whereas an ultrasonic sensor can detect the presence of an object by sending out ultrasonic sound waves and measuring the speed at which the waves return.

A PIR sensor is a type of electronic sensor that can measure the IR light radiating from objects in its field of view, while an ultrasonic sensor is a type of sensor that can measure the distance to an object using ultrasonic sound waves.

CONTENTS

1. Overview and Key Difference
2. What is PIR Sensor 
3. What Ultrasonic Sensor 
4. PIR Sensor vs Ultrasonic Sensor in Tabular Form
5. Summary – PIR Sensor vs Ultrasonic Sensor

What is PIR Sensor?

PIR sensor or passive infrared sensor is a type of electronic sensor that can measure the IR light radiating from objects in its field of view. Often, these sensors are useful in PIR-based motion detectors. PIR sensors are useful in security alarms and automatic lighting applications, as well. Typically, these sensors can detect general movement. However, it cannot give information on who or what moved. Therefore, we need an imaging IR sensor in this context.

When considering the operating principle of a PIR sensor, all objects typically having a temperature above absolute zero can emit heat energy in the form of electromagnetic radiation that is not visible to the human eye (because it comprises IR wavelengths) but is detectable using an electronic device designed for this purposes, such as PIR sensor. Therefore, we can detect the movement of people, animals, or other objects using these sensors.

There is a wide variety of applications of PIR sensors that causes these sensors to come in many configurations. Most commonly, PIR sensor models with numerous Fresnel lenses or mirror segments have a range of 10 meters and a wide field of view. However, there are some large PIR sensors made of single-segment mirrors, and they can sense changes in IR energy over 30 meters.

What is Ultrasonic Sensor?

An ultrasonic sensor is a type of sensor that can measure the distance to an object using ultrasonic sound waves. This is one of the best ways of sensing proximity and detecting levels with high reliability. Ultrasonic sensors typically use a transducer to send and receive ultrasonic pulses that tends to relay back information regarding the proximity of an object.

The operating mechanism of an ultrasonic sensor works by sending a sound wave having a higher frequency than the frequencies human can hear. The sensor has a transducer that can act as a microphone to receive and send the ultrasonic sound. Typically, these sensors use a single transducer to send a pulse and receive the echo. Moreover, the sensor can determine the distance to a target through the measurement of time lapses between sending and receiving of the ultrasonic pulse.

What is the Difference Between PIR Sensor and Ultrasonic Sensor?

The key difference between PIR sensor and ultrasonic sensor is that a PIR sensor can detect the presence of an object by sensing the difference between heat emitted by the movement of the object and the heat of the background, whereas an ultrasonic sensor can detect the presence of an object by sending out ultrasonic sound waves and measuring the speed at which the waves return.

The below infographic presents the differences between PIR sensor and ultrasonic sensor in tabular form for side by side comparison.

Summary – PIR Sensor vs Ultrasonic Sensor

PIR sensor or passive infrared sensor is a type of electronic sensor that can measure the IR light radiating from objects in its field of view. An ultrasonic sensor is a type of sensor that can measure the distance to an object using ultrasonic sound waves. The key difference between a PIR sensor and an ultrasonic sensor is that a PIR sensor can detect the presence of an object by sensing the difference between heat emitted by the movement of the object and the heat of the background, whereas an ultrasonic sensor can detect the presence of an object by sending out ultrasonic sound waves and measuring the speed at which the waves return.

Reference:

1. Burnett, Roderick. “Understanding How Ultrasonic Sensors Work.” MaxBotix Inc., Publisher Name MaxBotix Inc.Publisher Logo, 4 Mar. 2021.

Image Courtesy:

1. “Front-Fresnel type” By Jack LaRosa – Photographed and uploaded by me. (Public Domain) via Commons Wikimedia
2. “HC SR04 Ultrasonic sensor 1480319 20 21 HDR Enhancer” By © Nevit Dilmen (CC BY-SA 3.0) via Commons Wikimedia