Re: DS1820 temp sensor odd results
- From: "petrus bitbyter" <pieterkraltlaatditweg@xxxxxxxxxxxxxxxxx>
- Date: Tue, 24 Oct 2006 19:58:13 +0200
"Eric Yancey" <eyanceyATT@xxxxxxxxxxxxxxxxxxxxxxx> schreef in bericht
news:ZtednVgxpfMvkKPYnZ2dnUVZ_qOdnZ2d@xxxxxxxxxxxxxxx
Hello,
I recently installed a temperature monitoring system for my home workshop.
The primary goal is to monitor the heat capacity and dissipation of a
concrete slab floor with radiant heat tubing. When I installed the
heating
tubes before the concrete was poured, I embedded a fairly short (5 feet or
so) piece of PEX tubing to house a temperature sensor.
I built kit 145 from here: http://kitsrus.com/kits.html to interface with
four dallas DS18S20 sensors. One sensor measures ambient air temp, two
measure the temperature of the fluid entering and exiting the floor, and
the
fourth is inserted in the terminated PEX tube as described above.
The problem I'm having is that the 4th sensor is reporting flaky results.
I
replaced the original sensor but the replacement is exhibiting the same
behavior as the original. Here is some sample data:
07:45:00 78.35
07:44:30 74.07
07:44:00 71.15
07:43:30 72.50
07:43:00 75.20
07:42:30 67.42
07:42:00 74.62
07:41:30 67.32
07:41:00 75.97
07:40:30 71.15
07:40:00 73.96
07:39:30 69.80
07:39:00 69.80
07:38:30 78.01
07:38:00 73.96
07:37:30 57.87
07:37:00 70.57
02:01:00 61.25
02:00:30 86.11
02:00:00 84.76
01:59:30 59.56
Around midnight the sensor was reporting temperatures consistently around
60F which I believe is the actual temperature of the slab. From around
2:00AM this morning it started reporting inconsistent values, and now,
around 8:00AM, it is reporting temperatures anywhere from 57F to 78F,
which
I know is not correct (the temp of a concrete slab cannot fluctuate 30
degrees in 8 minutes).
Does anyone have any ideas on why this may be happening?
I apologize for the length of the message and thanks for any help!
Eric Yancey
Some thoughts.
Did you try to change the connection so to eliminate a faulty chip or a bad
connection? Same for the sensors.
Radiation (electromagnetic radiation) of any source can disturb the signal
from the sensor. Twist the wires carfully or try a piece of shielded cable
and ground the shield.
The sensor may not make a good thermal contact with the concrete, so your
results may reflect the temperature of the air in the tube instead of the
concrete around. You can try to close the tube using a cork or fill the tube
with fine dry sand (as for birds cages so you can remove it using a vacuum
cleaner).
petrus bitbyter
.
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