Re: [mowbot] Ultrasonic hardness measurement

Dave Everett (Deverett nospam at
Thu, 26 Sep 1996 16:07:20 +1000

robin nospam at wrote:
> Dave Everett <Deverett nospam at> wrote:
> > I set up an experimental breadboard to test the possibility of
> > differentiating between grass and concrete.
> Well done. I look forward to the results.
> Remember to test echos from a hard surface at an angle too.
> I suspect there will be enough scattering off hard facets for this
> to be a non-problem, but best check.

I will. Ultrasonic signals have an extremely high return rate for
incidence angles of 15deg and less. The signal drops off above 15deg in
an exponential fashion

Dave Everett                                Email: deverett nospam at
(c) 1996 - Copyright remains with the author unless explicitly stated