Ultrasonic SensorsBasic knowledge about ultrasonic sensors: Basic uses of ultrasonic sensors

Here we describe some precautions regarding aspects such as the housing and mounting to ensure efficient reception and transmission by ultrasonic sensors.

Precautions

①Do not impede vibration by the sensor.

If the sensor is enclosed in a housing, surround it with elastic material such as rubber or sponge that will not affect the vibration of the sensor itself. Select materials that will not become rigid when the temperature changes.

②Suppress reverberation.

Ensure that the vibration of the sensor is not conveyed to the board or housing. If such vibrations are conveyed to the board or housing, the housing may continue to vibrate after reverberations from the sensor have ended, extending the reverberation time.

③Do not impede the radiation of ultrasonic waves.

Keep the space above the sensor’s bevel (top surface) and the range of directionality free of obstructions.
Ultrasonic sensors propagate ultrasonic waves through the air. If the housing blocks the area above the sensor or extends into the range of directionality, ultrasonic waves will reflect off the housing and it will be difficult to actually measure the distance to objects.

Good and bad examples

Some good and bad examples using separate sensors for transmission and reception are illustrated here.
(These also apply to ultrasonic sensors of the transmission-reception combined type.)

Placement on the same board

Good exampleBad example

Using a hard housing
This can inhibit the vibration of ultrasonic waves or allow mutual vibration between the housing and sensor that may continue for a long time.

Placement on different boards


Good exampleBad example

Using a hard housing
This can inhibit the vibration of ultrasonic waves or allow mutual vibration between the housing and sensor that may continue for a long time.