These sensors are ubiquitous on sites like Amazon and AliExpress , making them incredibly easy to find for under $10.
For such a cheap component, it’s surprisingly accurate, often within 3mm . buy ultrasonic sensor online
If you have an Arduino or Raspberry Pi, it's a "plug and play" dream using the four standard pins: VCC, Trig, Echo, and GND . The Catch: HC-SR04 Ultrasonic Sensor Module - Quartz Components These sensors are ubiquitous on sites like Amazon