Two Ultrasonic Sensor Types

The following diagrams summarize the distinctions between proximity and ranging ultrasonic sensors:

Proximity Detection

An object passing anywhere within the preset range will be detected and generate an output signal. The detect point is independent of target size, material, or degree of reflectivity.

Objected detected - YES Objected detected - NO

Ranging Measurement

Precise distance(s) of an object moving to and from the sensor are measured via time intervals between transmitted and reflected bursts of ultrasonic sound. The example shows a target detected at six inches from sensor and moving to 10 inches. The distance change is continuously calculated and outputted.

Advantages of Ultrasonic Sensors

When used for sensing functions, the ultrasonic method has unique advantages over conventional sensors:

• Discrete distances to moving objects can be detected and measured.
• Less affected by target materials and surfaces, and not affected by color. Solid-state units have virtually unlimited, maintenance free life. Can detect small objects over long operating distances.
• Resistance to external disturbances such as vibration, infrared radiation, ambient noise, and EMI radiation.