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Re: Air resistance



At 12:06 12/15/97 -0400, Ludwik K wrote:
... air turbulences can act as
reflectors of ultrasonic waves. I verified this today by using an
ordinary hair dryer (CONAIR CORPORATION, model 088, at 1200W). ...

I am going to suppose that the phrase "...at 1200 Watts" is merely
a slip of the pen. As air temperature determines c,
better just to devote a small proportion of this power to the
blower itself. Turbulent or not, body movement
of the air mass in the path of the sonar is a direct vector addition
to the distance reading:

Blowing air up, toward the motion detector.

d(m)
1.569

... Blowing air horizontally
across the detection area produced a lessstrong fluctuations, as below:

d(m)
1.606
.... Ludwik Kowalski

An appropriate check for air mass movement is to next blow air down
from the sensor position towards the target, when you might find that
d(m) = 1.63 m

(All for a fixed target, of course...)

Regards




brian whatcott <inet@intellisys.net>
Altus OK