Anyone know if a PIR movement sensor will work through a double-glazed
window?

Thanks

Al

In article , AL_n
writes
Anyone know if a PIR movement sensor will work through a double-glazed
window?

No, glass blocks the long wavelength IR that they operate on.
--
fred
FIVE TV's superbright logo - not the DOG's, it's ********

"fred" wrote in message ...
In article , AL_n
writes
Anyone know if a PIR movement sensor will work through a double-glazed
window?

No, glass blocks the long wavelength IR that they operate on.
--
fred
FIVE TV's superbright logo - not the DOG's, it's ********


I was worried in case my alarm would trigger if someone was outside the
patio door - but it doesn't - can't get the indicator to trigger no matter
how much I dance around outside.

In article ,
"John" writes:
"fred" wrote in message ...
In article , AL_n
writes
Anyone know if a PIR movement sensor will work through a double-glazed
window?

No, glass blocks the long wavelength IR that they operate on.

I was worried in case my alarm would trigger if someone was outside the
patio door - but it doesn't - can't get the indicator to trigger no matter
how much I dance around outside.

With dual tech ones (combined IR and Microwave), microwave part can
see through glass, so you need to be careful in setting the microwave
sensitivity if that's going to be an issue.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article , Andrew Gabriel
writes
In article ,
"John" writes:
"fred" wrote in message ...
In article , AL_n
writes
Anyone know if a PIR movement sensor will work through a double-glazed
window?

No, glass blocks the long wavelength IR that they operate on.

I was worried in case my alarm would trigger if someone was outside the
patio door - but it doesn't - can't get the indicator to trigger no matter
how much I dance around outside.

With dual tech ones (combined IR and Microwave), microwave part can
see through glass, so you need to be careful in setting the microwave
sensitivity if that's going to be an issue.

I thought they were designed to trigger only when both the IR and
microwave elements trigger? Initially intended to reduce the risk of
false triggering in variable IR environs.
--
fred
FIVE TV's superbright logo - not the DOG's, it's ********

On Sun, 10 Oct 2010 09:55:16 +0100, fred wrote:

I thought they were designed to trigger only when both the IR and
microwave elements trigger? Initially intended to reduce the risk of
false triggering in variable IR environs.

Me to. An example of variable IR being looking at a window and the
sun popping out from behind a cloud.

--
Cheers
Dave.

In article ,
fred writes:
In article , Andrew Gabriel
writes
With dual tech ones (combined IR and Microwave), microwave part can
see through glass, so you need to be careful in setting the microwave
sensitivity if that's going to be an issue.

I thought they were designed to trigger only when both the IR and
microwave elements trigger? Initially intended to reduce the risk of
false triggering in variable IR environs.

That's a perfectly reasonable assumption, and one that I shared
until I actually used them. However, many of them have a feature
called anti-masking, where they detect that someone has sprayed
paint to mask them, by detecting microwave movement without IR
movement. Depending on the model, this either generates an alarm,
or a tamper fault. You can get ones without this feature, but it's
hard to tell as the datasheets often don't say.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article , Andrew Gabriel
writes
In article ,
fred writes:
In article , Andrew Gabriel
writes
With dual tech ones (combined IR and Microwave), microwave part can
see through glass, so you need to be careful in setting the microwave
sensitivity if that's going to be an issue.

I thought they were designed to trigger only when both the IR and
microwave elements trigger? Initially intended to reduce the risk of
false triggering in variable IR environs.

That's a perfectly reasonable assumption, and one that I shared
until I actually used them. However, many of them have a feature
called anti-masking, where they detect that someone has sprayed
paint to mask them, by detecting microwave movement without IR
movement. Depending on the model, this either generates an alarm,
or a tamper fault. You can get ones without this feature, but it's
hard to tell as the datasheets often don't say.

That's useful to know thanks.
--
fred
FIVE TV's superbright logo - not the DOG's, it's ********