AVR-Chat

At 08:58 PM 7/15/04 +0000, you wrote:
>The only fast change I can forsee is watering.  When one waters a
>plant, the soil temperature changes rapidly and with large variations
>from the previous point.

The differential approach would catch that just fine though.  The only 
question would be the time resolution you would want.  You could sample 
fairly quickly and only record those that change more than x% from the 
previous record.  When sudden changes due to watering occurred you might 
get sample every 30sec or so rather than every 20min.  As a refinement you 
might want to set a minimum frequency of data collection so that slowly 
changing parameters are profiled more precisely.  IE something like

last = getAD(SOILMOISTURE);
last_measured = 0;
interval = 0;
while( keep_running != 0) {
    wait( 1ms)
    interval++;
    nextval = getAD(SOILMOISTURE);
    if( ((nextval > ((last*11)/10)) || (nextval < ((last*9)/10)) || 
(interval > MAX_PERIOD)) {
         last = nextval;
         last_measured += interval;
         interval = 0;
         store_data( last_measured, last);
         }
    }

>ah, the nature of research...  who knows what the answer will be.
>Seems to be a simple project though.

I have some suspicions.  But you are right it should be simple and it might 
even provide some real insight into the plant's biology.

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,
be they legal, genetic, or physical.  If you don't believe me, try to
chew a radio signal. "

                         Kelvin Throop, III