Ultrasonics and People Detection
All of the MaxBotix® Inc. ultrasonic sensors are capable of detecting people. The range that the MaxSonar® family of sensors is capable of detecting people varies from sensor to sensor. When choosing a sensor that you want to use for people detection, we recommend viewing the beam plots of the sensor for the approximate range of people detection.
People detection generally falls between grid pattern A and grid pattern B when the sensor is perpendicular to the person. Typically a person will reflect the same amount of ultrasonic energy as a 1 inch diameter dowel. Even though people are physically large targets, humans are a soft target that absorb a large amount of ultrasonic sound and reflect only a fraction of the ultrasonic sound.
It has been observed that because of the soft target nature of people, occasional range readings may be incorrect. This may happen even though the majority of reported readings are accurate.
People detection is not perfect. Another thing to take into consideration is the ultrasonic reflection when detecting people can vary from person to person. The amount of ultrasonic sound that is reflected can be dependent on what a person is wearing. If a person is wearing a belt with a large flat hard belt buckle, the sensor may be able to begin detecting the person at further distances. However, if they are wearing sound absorbant material like a thick wool jacket or thick sweatshirt the sensor may not detect a person until they are within a couple feet of the sensor.