Alberto Smulders wrote:
>
> Hi Rick !!!
>
> Another very interested person here, looking for a cheap method to measure
> contents in grain and oil storage bins - should be a kind of ultrasonic
> rangefinder, maximum range around 10...12 meters, ruggedized for use in an
> industrial environment, some serial communication means for rather long
> distance (up to 1 km or so) if possible with unique address for
> interrogation, and.... (hmmm... am I asking too much ????)
>

no , not at all .
I make my on board car computer for my jeep and encountered the
same problem (noisy environment , lack of cables)
and came up with a simple idea (I guess I reinvented the wheel
but who cares) all units have serial numbers (one for the digi-compass
one for the dallas thermometer interface , one for fluid levels
and so on)
when the main system addresses one of them it wakes up (everybody else
goes sleepin') returns the required data and signs off with a 0ffh
the master waits for this (in case of timeout , displays the error)
the signoff is the reset for all the other systems .
now everybody waits for the next selector byte . and so on .

I guess this is not too complicated (most of the ideas came from the
dallas system , and biological analogs )

bye
charley