Engenharia Mestra de Sistemas Sociedade Ltda wrote:
>
> I know that 40kHz is a standard for sonic range finders, but my question is:
>
> Has anyone tried a lower frequency ? How low can we get still keeping quality
 ?
>
> TIA,
>
> Pedro Drummond


Lower frequencies work even better, but you encounter a few problems:

1. transducer geometries grow large, especially if you need
directionality
2. people start to get annoyed, since the transmitter will become
audible to some people and animals
3. transducer ringing duration, which often determines minimum range for
echo sounders, gets longer
4. phase measurements may become less precise as the zero-crossing slope
of the signal gets more shallow

--

Paul Mathews, consulting engineer
AEngineering Co.
optoeng@whidbey.com
non-contact sensing and optoelectronics specialists