Subject:
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RE: Cheap air flow sensor
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Tue, 16 Jun 1998 14:41:25 GMT
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Original-From:
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Brett Anthony <anthonyb@ecs.csus.edu*stopspammers*>
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Viewed:
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1174 times
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The classic small air flow sensor is a hot-wire-anemometer. Just position a
short piece of very fine wire in the airflow and normal to it, run a
constant current thru it, and measure the voltage change due to the cooling
effect of the airflow. Works great. Unfortunately, the sensing wire is
ordinarily platinum (!) due to it's desireable resistivity/temperature
characteristics and relative inertness, however, cheaper wire may work. It
must be VERY fine wire, however.
The classic, and cheap, humidity sensor is human hair, but measureing it's
change in length (which is the variable) may be a problem. Alternately, you
can make one by making a pair of parallel traces on a bit of PC board, about
1mm wide and 0.5mm apart, and a few cm long. Fold these back upon
themselves serpentine style to keep it small; the ones I've seen are about
1cm square. Now all you have to do is measure the capacitance change... I
can't find these in any of my present catalogs, but I know I've seen them.
fischertechnik used to supply them, which is where I got mine.
Brett Anthony
Research Technician
School of Engineering and Computer Science
California State University, Sacramento
e-mail: anthonyb@ecs.csus.edu
phone: (916)278-6253
fax: (916)278-5949
address: Brett Anthony
E&CS, CSUS
6000 J St
Sacramento CA 95819-6023
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