Ultrasonics refers to signals that are above the human hearing span (>20 kHz), and usually in the 40- to 70-kHz range. These signals are used like radar—they’re radiated toward a target and reflected back to the source. By measuring the time between the originally radiated signal and its reflection, and knowing the speed of sound, the distance to the target can be computed.
This makes ultrasonics a potential alternative to microwave or millimeter-wave (mmWave) radars. It’s especially useful in shorter-range applications, and typically costs less than radar. If you’re looking for a sensor that can not only detect the presence of a target but also tell you how far away it is, ultrasonics may be a good choice for you.
Ultrasonics has found its way into a wide range of applications, the largest sectors probably being proximity detection and range measurement. Others include liquid-level detection in tanks, flow-measurement systems, and imaging products. Most of the newer applications address the consumer electronics, automotive, and industrial/robotics fields. Those are the focus of this article.
Home owners want to automate their homes these days. Thermostat and lighting controls are the most popular, but other conveniences are ceiling fans, video doorbells, garage-door openers, and security alarms. All of these can probably be improved by adding some form of proximity detection. This allows lights to be automatically turned on or off, heating and air conditioning to be adjusted based upon occupancy, and security alerts.
Another potential application is proximity detection for the popular voice-activation/response hubs like Amazon Alexa, Google Home, Apple HomePod, and others. These devices could sleep and conserve power if no one is nearby, but could wake up if presence is detected.
A current popular application is robotic vacuums—machines that automatically vacuum your floors. Most use ultrasonics to navigate around objects that are successfully detected by ultrasonic transducers. Multiple transducers give these devices a full 360-degree view, allowing them to easily navigate even the most complex rooms.