> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On
Behalf
> Of Jinx
> Sent: 01 April 2009 21:48
> To: Microcontroller discussion list - Public.
> Subject: Re:[EE] Temperature detection with a PIR sensor
> 
> > Are you sure you were really measuring the air and not hard objects
> > that it cooled down?
> 
> I might suspect that the cold air was getting between the sensor and
> the warm objects. I don't know if the temperature of a body of air
> can be measured directly, but it could be that its influence on other
> things in the environment can be
> --

It is apparently possible for drafts to set of the PIR sensors used in
security systems.  

ISTR that whilst PIR sensors are only sensitive to changes in incident
radiation, they can be used in conjunction with mechanical choppers to
measure absolute levels.

Regards

Mike

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