Ultrasonic vs. Infrared (IR) Sensors: A Detailed Comparison

This article compares ultrasonic sensors and infrared (IR) sensors, highlighting their differences and how they work. Both technologies utilize frequencies within the electromagnetic (EM) spectrum for various applications.

Ultrasonic frequencies reside above 20 KHz, while infrared frequencies range from 430 THz down to 300 GHz.

Figure 1 and 2 illustrate the ultrasonic and infrared frequency ranges within the electromagnetic spectrum.

Ultrasonic Sensors

Figure-1 : Ultrasonic sensor

• As mentioned, ultrasonic frequencies fall above 20KHz in the EM spectrum. A device using these frequencies is known as an ultrasonic sensor.

• Ultrasonic sensors are used in various applications, including distance measurement, automatic car parking systems, humanoid robots, sonography (medical imaging), and ultrasonic flaw detectors.

• An ultrasonic sensor has two main parts: a transmitter and a receiver. The transmitter converts electrical energy into sound waves, typically at 40 kHz, and emits them into the air. The receiver then detects the echo of the reflected sound waves from an object and converts it back into electrical energy. Based on this, calculations are performed according to the sensor’s specific application.

• Refer to the advantages and disadvantages of Ultrasonic sensors for more details.

Infrared (IR) Sensors

Figure-2 : Infrared sensor

• Infrared frequencies range from 430 THz to 300 GHz in the EM spectrum, with wavelengths from 700 nm to 1 mm. A device using these frequencies is known as an infrared sensor.

• Like ultrasonic sensors, infrared sensors also have a transmitter and a receiver. When voltage is applied to the IR LED of the transmitter, it generates infrared waves.

• The infrared transmitter emits these waves over a short distance. The receiver detects any reflected infrared waves and generates a corresponding voltage. If there is no object nearby, there won’t be any reflected waves, and the receiver won’t output any voltage.

• If an object is present, the receiver detects the reflected wave and produces a voltage accordingly. Comparators or microcontrollers then process these voltage levels for further analysis. This is how infrared sensors work.

• Refer to the advantages and disadvantages of Infrared Sensors for more details.

Ultrasonic vs. Infrared Sensors: Key Differences

The following table highlights the differences between ultrasonic and IR sensor devices. For comparison, the SHARP GP2Y0A21YKOF is used as an example of an infrared sensor, and the Multicomp HC SR-04 as an ultrasonic sensor.

Table 2 below provides a generic comparison between ultrasonic and infrared sensors.