[phoenix-project] 6.4) Temperature Measurement, PT100
- From: Georges Khaznadar <georges.khaznadar@xxxxxxx>
- To: ozhan fenerci <o_fenerci@xxxxxxxxxxxx>
- Date: Fri, 12 Jun 2015 19:25:23 +0200
Hello Ozhan,
ozhan fenerci a écrit :
c) Is it possible to use any temperature probe other than PT100. Because
using a opamp makes difficult for students.
In my laboratory, we are commonly using LM35 probes. To make them
submersible, we are using small PVC tubes collected in the waste bin
(see
http://commons.wikimedia.org/wiki/File:Cartouche_d%27encre_vides.JPG).
We cut the end of the tube which bears a hole, to have a cylinder open
at one end, with a flat bottom.
After soldering the three pins to a cable with two wires and a metallic
shield, we put the component into the tube filled with slowly curing
epoxy resin, the excess resin flows out of the tube, and the remaining
resin becomes hard 12 hours later.
According to
http://www.ti.com/lit/ds/symlink/lm35.pdf,
- you can use 4 to 30 V to feed the LM35 sensor
- it drains very few current; so voltage from OD1 is OK.
- the sensitivity is 10 mV by degree. As the accuracy of expeyes DC
inputs is 5 mV when you use a conversion with 10 bits, you can know
the temperature with an accuracy of 0,5° C without amplifying.
- the linearity is very good for such a cheap component (+-0.15°C, 3 €
in small quantity at my local store)
- with no external component, you can measure temperatures in the range
2°C to 150°C (schematics are on page 1)
Best regards, Georges.
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