Contact: Bruce
Tel: +86-755-22 666 190
Fax: +86-755-29 043 136
E-mail: sales@ultrasonic-sensors.net
Skype: longsunac
Address: Room A1, 6/F, Bldg. No. 531, Bagua 3rd Road No. 277, Futian District, Shenzhen, China 518029
2. Feature of ultrasonic sensor
The ultrasound can't be heard by the ear, its frequency is over 20KHz, the basic feature of ultrasonic sensor is the following:
Wavelength and radiation
The speed of the wave shows with frequency multiply with wavelength. The sound wave spreads very slow in the air, about 344m/s. In this condition the wavelength is short and means that can get higher distance and direction resolution.
Reflect
Detecting something is existance or not, ultrasonic wave must get the reflect from its surface. We can easily find these things, such as metal, wood, concrete, rubber and paper because they can reflect nearly 100% ultrasonic wave, while for the cloth, cotton, floss etc, it is difficult for us to tell them through ultrasonic wave cause they can suck up the wave. Meantime, due to irregular reflect, we may have some difficulty to detect those objects that vibrate heavily on the base.
Temperature effect
The speed of sound wave shows the following formula :
C=331.5+0.067t (m/s)
t=temperature, it is to say that the speed of sound wave changes with temperature. Therefore, if it is always necessary to check up the surrounding temperature if measuring the distance exactly from the object.
Attenuation
When the ultrasonic wave spreads in the air, its intensity changes with distance to decay proportionaly, because the diffraction phenomenon caused by the proliferation of the spherical surface loss, it is also as a media to absorb the energy.
