On Thu, Apr 29, 2010 at 01:48:05PM -0700, Marc MERLIN wrote:
> > In my case a dry sensor at 21.65C measure a current of -0.129375
> > The supply voltage is measured at 4.8V
>
> Short version:
> Paul, do you think you could talk to Eric on producing a "moisture"
> variable that is based on the current value and temperature corrected?
>
> I ran a test where I had a fully wet sensor, I took it out of the glass
> of water, put it in a warmer place (5C warmer at most) and the current
> value went from -1.38687 all the way to -1.45187 just because of the
> temperature rise.
> Eventually things stabilized and the humidity went down again as the
> sensor started drying up further.
I did more tests this weekend.
First question was: does the temperature of the measuring board affect the
moisture current readout?
Answer: not a whole lot. Temperature changes caused barely noticeable
increase of current readings, at the level of noise, really.
Second question. How about the probe temperature?
Oh boy, the probe temperature when wet gave me reading changes over
50%(!) just based on the water temperature.
current board temp (F)
wet icy: -1.13 70.475
wet ambiant: -1.3825 70.025
wet warm: -1.72063 70.7
I suppose the fact that humidity probes vary with temps is not new, but
the moisture probe doesn't seem temp corrected at all (not even the board
measured temp in case I was going to burry the board with the sensor to get
soil temp).
I realize that soil temperatures don't vary as extremely as in my water glass
case, but dirt that is getting warmer and dryer giving a constant current
reading for a while as rising temp cancels out lowering humidity, is not too
ideal.
Do you think it would be doable to make a moisture reading that is more or
less temperature corrected, at least using the temp seen on the board?
Thanks,
Marc
--
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems & security ....
.... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/
------------------------------------------------------------------------------
_______________________________________________
Owfs-developers mailing list
Owfs-developers@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/owfs-developers
