I'm doing something to monitor lake temperatures that I am currently working on.
For your application, it is a good design. There shouldn't be much difference
in
your water temperatures at different water levels. Any lighting could affect
your air
temperatures, but might actually "help" your application. If you were to
measure the
water height once per day say at 12pm, you could have a timer turn on a light
right before 12pm
and you would see the air temp chips react very quickly to the light/heat
generated. This would probably
insure that your water and air temperatures are never the same.
A couple of comments:
1. You are going to know the water heights, so you shouldn't need to do an
average.
2. Soldering to accurate length/distance/height.....tedious.
3. Thin layer of epoxy over chip, so temperatures react quickly.
3. Height of water Algorithm. Could be very elegant....as you fill with water,
you can see the temperature change
on a chip quickly to align with water temperature.....
Couple of questions
1. How do you know how long to have the water on to fill.
2. What's the failsafe on preventing overflow of aquarium?
----- Original Message ----
From: Scott <[EMAIL PROTECTED]>
To: [email protected]
Sent: Sunday, September 21, 2008 8:29:12 AM
Subject: [Owfs-developers] Thoughs on a temp sensor based liquid level monitor?
I use OWFS to monitor various parameters of my saltwater aquarium. One
of the biggest things I'd like to monitor is the approximate height of
the water in my sump to know when additional water needs to be added,
etc. It also gets a little bit interesting because I have baffles in
my sump and filter floss between them to filter particulate matter as it
goes through the baffles. As the filter floss gets plugged with debris,
it restricts the water flow creating a difference in heights on each
side of the baffle. I can't just monitor one side or the other and
assume the water level because the two levels may be identical (zero
restriction with newly replaced filter) or up to ~8 inches different
(plugged filter in desperate need of replacement). I need to know the
level on both sides and average it to get a true standard volume baseline.
I've thought about using an array of float switches and a GPIO chip to
monitor which switches are open/closed to deduce the water level, but
there's several reasons why I haven't gone that route: reliability,
space, and resolution to name a few. The other day I came up with an
alternative - use an array of temp sensors to monitor the differential
temperature between the air and water to approximate the water level. I
already track both those temps, giving me a sort of calibration standard
for comparison. As long as the temp sensors are spaced at a known
distance, and the starting height is known, I just write a script to
read and compare all the temps. The water height should be between the
two adjacent sensors with temps matching the known air/water temps. The
resolution of the array would be determined by the distance between and
number of temp sensors in it.
I'm I computer guy, but definitely no EE so I thought I'd bounce this
design off the list to see if there's anything I should add to the
circuits I'm not thinking of. I'd probably (since I already have a slew
of them) use DS18B20 chips all wired in parallel with a network branch
(DS2409) to separate the two sides and logically segregate the arrays
from the general temp probe population. Each array of temp probes would
be wired up and then completely encased in epoxy to protect it from the
water. I've already done this with TO-92 form factor temp sensors and
it works quite well.
Here's a diagram I put together with my design. Let me know if anyone
has thoughts, etc on it:
http://bytality.com/offsite/OWTemp_depth_sensor.png
-Scott
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