ultrasonic sensors

[sss]

i'm still trying to make a distance measuring device , so i've desided to use ultrasonic sensors ....
does someone know how to translate the transmitting spl level to effective distance the sensor can be used?
for example transmitting spl is 120db
what is the max usable distance for the sensor?

 

[dnsey]

I can't answer your question specifically, but it's probably longer than you expect. A few years ago, I was designing a low-powered ultrasonic alarm, and couldn't understand why the receiver kept showing an output when nothing in the room was moving. Eventually I traced it to the doors, about 10m away, swinging in the breeze by about 1cm!

 

[jcx]

http://www.acroname.com/robotics/info/articles/sonar/sonar.html

from google search: polaroid ultrasonic sensor
also

http://www-personal.umich.edu/~johannb/Papers/paper93.pdf

and lots more

sonar/radar equations are well known but complex, what's your directivity, target scattering coeff, receiver sensitivity, ect.

experimentation is much easier than accurate modeling - judge feasibility by reported performance of similar systems

 

[clem_o]

Hi,

Transmistting SPL can't be directly translated to max distance. You need to factor the medium losses, the reflection loss (this is determined by the impedance difference between the medium and the reflecting surface) , the receive sensitivity, the beamwidth of the transmitter, among other things...

Cheers!

 

[phase_accurate]

A little off topic (but only slightly): There seems to be a convenient single-chip solution available that doesn't need much additional hardare apart from PSU and sensor.
I can try to find the type of this IC if you are interested.

Regards

Charles