John said:
We do something quite similar with our water level and temperature wireless
short range telemetry system. Could fairly simply be adapted to your
application. How many do you want?
Regards
John
http://www.electrosense.com.au
That water level system with the neat sensor arrangement, wireless link and
high measurement resolution is very impressive John.
In this situation I'm proposing to install up to 6 clusters of 3 or 4
sensors each buied at different depths. Each sensor, in the first instance,
will be a gypsum block (2 wires stuck in a lump of plaster) measured using a
555 that generates a frequency proportional to the resistance in the block.
A PIC will count the frequency of each sensor and then send the results to
the logging computer which will generate a web page showing the data both
numerically and graphically.
If the system works, the gypsum blocks will be replaced by Watermark sensors
that allegedly last up to 10 years, but cost US$30 each
At the moment, having looked at the project that Lionel posted earlier, I'm
leaning towards a transceiver based system where the logging computer polls
each client to report, thus avoiding collisions. I think I'll have a bit of
a play with the little UHF tranceiver module that Oatley flogs and do a bit
of testing - I have to use a micro for the moisture sensing, so it'd be good
if I can get it to do the comms as well.
That said, I might very well get jack of trying to get the comms bit to work
(which is why I was looking about for some kind of module).