Why Your Ultrasonic Sensor Lies to You

Why Your Ultrasonic Sensor Lies to You You mount an HC-SR04 ultrasonic sensor. You write the code. You measure the distance to the object. The object is 50cm away. The sensor reads 48cm. You move it to 100cm. The sensor reads 97cm. Close enough, right? Then you try to use it in your interactive installation. Someone walks in front of it. The sensor reads 30cm. Someone else steps behind them. The sensor reads 28cm. Or 35cm. Or nothing at all. The HC-SR04 is not lying to you. But it is not telling