No the lack of output idea does not roll. I have tested this on portable
alarms. Its the movement of differing temperature things that sets them
off, but many have some kind of logic to try and stop the issue. I remember
one particular occasion where a small shrub was partly across a window. The
pir could see the window from its position. As long as there was no wind,
all was well as the window was warmer but always the same place, introduce a
wind though, and the evergreen shrub swayed in front of the window making
the false trigger occur. Re aim the sensor to not see the shrub and all was
well again.
Brian

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The Sofa of Brian Gaff...

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"Fredxx" wrote in message
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On 10/12/2019 23:47:02, Terry Casey wrote:

snip

Has anybody got any ideas why an IR detector should play up in
the presence of high winds and then work normally when they
drop?

In high winds most surfaces would become uniform in temperature. Your coat
would quickly become the same the wind temperature.

IR sensors rely on seeing a low frequency temperature variation through
their multiple lenses. If anything is a uniform temperature the sensor
will not provide any output.