Infrared passing through glass -- the facts!
aa...@_no.spam.deltanet.com
>What no one has mentioned in this long thread is that there are different
>frequencies of infrared. "Far" infrared is what motion detectors "see" and will
>not penetrate glass. Infrared frequencies that TV remotes use are a lower
>frequency infrared that will penetrate glass and can be detected by cctv
>cameras.
Finally! Here are some additional details:
The infrared spectrum is considerably larger than the visible spectrum.
Visible light has wavelengths ranging from about 400 nanometers (violet)
to about 700 nanometers (red). The infrared spectrum starts at about
700 nm and goes up to 10,000 to 20,000 nm, depending on who you talk to.
Consequently, it shouldn't be surprising that there are different types of
infrared energy, with different properties.
If anyone doubts that _some_ infrared can pass through glass, just think
about fiber optics. Optical fiber is nothing but ultra-pure glass. The
standard wavelengths for fiber are 850 nm, 1300 nm, and 1550 nm, all
in the "near infrared" band. Photoelectric beams also operate in this
range, because they use similar light sources (LEDs or laser diodes).
Consequently, these types of IR pass through glass just fine.
Another proof: as someone pointed out earlier, a monochrome camera
will pick up the flashes of light from a TV remote -- through the
glass lens of the camera!
In fact, near IR passes through ordinary glass slightly better than
visible light does (_very_ slightly better).
I was unable to find any exact specs on the range of wavelengths
detected by a passive infrared detector. However, I did learn that
room temperature objects emit most of their infrared energy at
around 10,000 nm, which is in the "mid IR" band. So passive
IR devices probably detect similar wavelengths.
Glass, in any reasonable thickness, is opaque to wavelengths longer
than about 2000 nm. In fact, other materials must be used as the
"windows" in IR sensors and instrumentation which are intended to
detect the longer wavelength infrareds.
Bob
fortunately you did it first and saved me the research. In addition to your
information certain infrared (heat energy) frequencies which do not pass
easily through "glass" can pass through by conduction rather than radiation.
In other words they make the glass hot.
The point of this discussion in my opinion would be for the purposes of
either for intruder detection through glass or prevention of false alarms.
I wouldn't ever reccomend a "standard" pir for intruder detection through
window glass. As to false alarms. There are a number of things which can
cause falsing through a window that is closes to and in the direct view of a
PIR motion sensor.
It is a good idea to review the manufacturers specifications on any motion
sensor you intend to use for its capabilities and limitations.
Most manufacturers are more than willing to give you the information you
need on their products.
aa-2@_no.spam.deltanet.com wrote in message
<6uf3dm$r...@journal.concentric.net>...
hoffman
Like others, I've been wanting to get into this for a week. In fact
there are some brief technical details in the alt.lasers and
sci.optics.fiber in regards to a message I posted. If you want to
know about glass and infrared.. Then the fiber optic newsgroup
is the place you go for more authoritative info..
Anyway, as anyone who deals with lasers and FO knows
near infrared will go through glass just fine, with only
minimal attenuation.. It is the far infrared which is seriously
attenuated by common window glass.. Although I still did
not get much in the way of exact details, it seems that
infrared which emmited from people is broadband but is
mostly focused in the region of mid infrared to far infrared..
A small amount of IR emanations from your body will still
go through window glass but it will likely be too weak for
the PIR detector to trigger if the detector is far enough away.
David J. Rosso
>> The infrared spectrum is considerably larger than the visible spectrum.
>
>Like others, I've been wanting to get into this for a week. In fact
>there are some brief technical details in the alt.lasers and
>sci.optics.fiber in regards to a message I posted. If you want to
>know about glass and infrared.. Then the fiber optic newsgroup
>is the place you go for more authoritative info..
What does all this really matter, the original poster simply wanted to
know if a infrared motion sensor could pick through glass, the plain
and simple answer to that is no. Standard security PIR's do not work
through glass, whether or not other infrared passes through glass was
not the issue in question.
David J. Rosso - http://apk.net/~rosso
Fight Spam! Join CAUCE! - http://www.cauce.org
Outlaw Junk Email! Support HR 1748
= Chat with me using AIM: David1732 =
hoffman
> wanted to know if a infrared motion sensor could pick through
> glass, the plain and simple answer to that is no.
Awww.. Your taking the fun out of this.. A Yes/No answer is
nice... But... sometimes its just nice to know the specifics
regarding how something work. The details may not interest
the original poster, but I know it interests a few others.
Charles Booth
another.
Back in the 1970's, before PIR's, we installed Arrowhead and DS
"pulsed infrared photoelectric eyes."
Some of the homes in which we placed them, contained interior
multi-paneled glass doors, usually a double set separating the front
halls from the adjacent dining and living rooms.
We would shoot the beam from the outside wall of the dining room,
through the front hall, and into the outside wall of the living room.
Because the doors would be closed from time to time we were especially
carefull to see that the beam went through the glass of each set of
doors at a point where the beam would not be obstructed by the
muntins.
We never had a problem with infrared passing through two panes of
glass in these situations.
news.earthlink.net
use a low band infrared signal, which is close enough to visible light to
allow most of it to pass through.
Infrared energy (heat energy) of the wavelengths that OUR commonly used
PIR's are designed to detect does NOT penetrate glass well. I'm actually
quite surprised that many of our fellow "pro's" here know so little about
the technologies behind the products we sell.
Kudos to those who have provided the correct information for the original
poster- and might I suggest that those who gave anomolous or misinformed
information brush up on those tech manuals and dusty schoolbooks. Let's
strive toward being better as an industry, so as to stave off the
ever-increasing trend of DIY (Yes, Robt., some may be able to do a good job,
but most folks I've met need my services.) and fly-by-night jobs.
Thanks.
<snip>
>Back in the 1970's, before PIR's, we installed Arrowhead and DS
>"pulsed infrared photoelectric eyes."
>
>Some of the homes in which we placed them, contained interior
>multi-paneled glass doors, usually a double set separating the front
>halls from the adjacent dining and living rooms.
>
>We would shoot the beam from the outside wall of the dining room,
>through the front hall, and into the outside wall of the living room.
>Because the doors would be closed from time to time we were especially
>carefull to see that the beam went through the glass of each set of
>doors at a point where the beam would not be obstructed by the
>muntins.
>
>We never had a problem with infrared passing through two panes of
>glass in these situations.
<snip>
David Norris
Charles Booth wrote
>We never had a problem with infrared passing through two panes of
>glass in these situations.
Hey, we cant have the facts be getting in
the way of opinions!
David
ALARMIN
In article <6uirk7$1dr$1...@news1.rmi.net>, "David Norris" <dlno...@rmi.net>
writes:
>Subject: Re: Infrared passing through glass -- the facts!
>From: "David Norris" <dlno...@rmi.net>
>Date: Sat, 26 Sep 1998 07:59:26 -0600
OK ......... NOW .......... to continue .................
now that we've determined that the infrared energy that our industry PIR's
detect cannot easily penitrate glass ................
AND ................
now that we've determined the mirrors can reflect the infrared energy and trip
a PIR detector ........
Now think about how a mirror is made ....... a piece of glass .....silvered on
the back side .......
How does the infrared energy pass through the mirror glass ...... reflect off
of the silvering on the back ....... pass back through the glass and activate
the PIR ???????????????
aa...@_no.spam.deltanet.com
>
>OK ......... NOW .......... to continue .................
>
> now that we've determined that the infrared energy that our industry PIR's
>detect cannot easily penitrate glass ................
>
>AND ................
>
>now that we've determined the mirrors can reflect the infrared energy and trip
>a PIR detector ........
>
>Now think about how a mirror is made ....... a piece of glass .....silvered on
>the back side .......
>
>How does the infrared energy pass through the mirror glass ...... reflect off
>of the silvering on the back ....... pass back through the glass and activate
>the PIR ???????????????
I'll throw out some ideas here, but I don't know for sure whether I'm right.
We know that ordinary glass is opaque to the infrared wavelengths which
passive infrareds detect. This means the infrared is either absorbed by the
glass, or reflected from it.
I'm guessing that the infrared is actually reflected from the _front_ surface
of the mirror, rather than from the silver on the back of the mirror.
As some sort of proof of this, I've had sunlight go through window glass,
reflect off of a clear glass coffee table, and trip a ceiling mounted IR.
Most of the visible light would pass straight through the glass; it appears
some of the IR, at least, reflected off of it.
DepthExplr
ala...@aol.com (ALARMIN) writes:
>OK ......... NOW .......... to continue .................
> now that we've determined that the infrared energy that our industry PIR's
>detect cannot easily penitrate glass ................
>AND ................
>now that we've determined the mirrors can reflect the infrared energy and
>trip
>a PIR detector ........
>Now think about how a mirror is made ....... a piece of glass .....silvered
>on
>the back side .......
>How does the infrared energy pass through the mirror glass ...... reflect off
>of the silvering on the back ....... pass back through the glass and activate
>the PIR ???????????????
Thi IR does not pass through the glass and reflect on the silvering of the
mirror, it reflects off the glass surface, it never reaches the sivering back.
It will reflect the same way on lots of different materials like plastic,
metal, coated woods, glossy paper, etc.
MT
Adenco
how do you guys explain a pir with mirror optics?? example ds-774 or 938, it
dosent go through the glass, it reflects off the surface.
james barnes
denco security lc
KAREN8927
And continuing the "glass and infra-red saga, James Barnes asks the following
question:
James,
I think if you make a closer inspection of the "mirror" in the pir models you
questioned, you will find that the "mirror" is not a real glass mirror, but is
in fact a "plastic reflector" (for lack of a better word)
So I don't think this type of IR fits in to the ongoing question/saga of "does
the IR energy bounces off the front of the glass or off the "silvered" back
side of a mirror"
Karen
(Eat or remove lunch meat to reply)
"Lately it occurs to me what a long...... strange trip its been".
(Where the hell am I and pleas tell me, why does the Greatful Dead keep
following me all around the country?)
Lawrence Dorsey
DepthExplr wrote in message
<19980926171700...@ngol06.aol.com>...
I find this whole conversation curious, ir going thru glass, reflecting off
of glass?
Pir "Passive Infared" Passive meaning it does not send it just looks. I have
yet to see one that picks up thru glass. When the pir is being used to
"detect" an "intruder" they usually are on the correct side of the glass.
Manufactures know this i am sure. Thus, they must take the glass situation
into account.
Beams are beams, its a light source and will go thru glass. The lenses on
the beams act as filters i believe.
Back to PIRs, They look for a change in temperature, hot to cold, cold to
hot. Now, if you stand in front of a mirror and the sun hits the mirror, you
will feel the heat of the sun. So will the pir. Shinny surfaces can be a
problem.
I ran into a false alarm situation a couple of years ago that was quite
interesting. I had a customer who was having cronic false alarms in the
evening. Seems the sensor had been changed numerous times with no positive
results. The problem turned out to be a smoldering fireplace. They had put
out the fire, turned on the alarm and went to bed. Masked the fireplace out
so Santa could get down, yet he could not steal anything.
Drafts thru the wall where the wiring comes thru can be a problem at times.
Seal the sensor openings properly.
Any! light plastics such as used in packing in a factory change temperature
rapidly when gas heaters come on. Now I don't know about the rest of the
world but here in Canada we get all kinds of weather and all kinds of
strange things happen. Kind of when off subject here but i hope this helps
someone. Interesting group you people have going here.
Lawrence Dorsey ldo...@idirect.ca
Tom Brown
KAREN8927 wrote in message <19980927051639...@ng74.aol.com>...
>James,
> I think if you make a closer inspection of the "mirror" in the pir models
you
>questioned, you will find that the "mirror" is not a real glass mirror, but
is
>in fact a "plastic reflector" (for lack of a better word)
>
Arrowhead and others used real, silver-backed mirrors in their early and
quite effective detectors.
Bob
plastic mirrors were already deeply entrenched then. At least manufacturer
supplied a plastic mirror to snap into the front of their PIR when
adjusting. It had the view of the lens marked on the mirror surface.
Tom Brown wrote in message <6umseo$9tb$1...@oak.prod.itd.earthlink.net>...
electrnpshr
but I think I did learn something.GFK.
On Mon, 28 Sep 1998 23:41:03 GMT, "Robert L Bass" <alar...@Home.com>
wrote:
>
>aa-2 wrote:
>> (ALARMIN) writes:
>>>
>>> now that we've determined that the infrared energy that our industry
>PIR's
>>>detect cannot easily penitrate glass ................
>>>
>>>AND ................
>>>
>>>now that we've determined the mirrors can reflect the infrared energy and
>trip
>>>a PIR detector ........
>>>
>>>Now think about how a mirror is made ....... a piece of glass
>.....silvered on
>>>the back side .......
>>>
>>>How does the infrared energy pass through the mirror glass ...... reflect
>off
>>>of the silvering on the back ....... pass back through the glass and
>activate
>>>the PIR ???????????????
>
>
>Here's my best guess based on my use of PIRs and (limited) understanding of
>light. The IR energy emitted by a person is of a portion of the spectrum
>which doesn't readily pass through window glass. However, there are other
>sources of IR (sunlight, halogen headlamps, etc.), which include portions of
>the IR band which do pass through such glass quite nicely.
>
>Unfortunately, although the PIRs don't usually detect humans on the other
>side of the glass, they do detect (and false from) such other IR sources.
>Does this make sense to you? I hope so because I'm about out of ideas.
>
>Regards,
>Robert
>
>=====================>
>Robert L Bass
>Bass Home Electronics
>http://www.BassHome.com
>80 Bentwood Road
>West Hartford, CT 06107
>860-561-9542 voice
>860-521-2143 fax
>=====================>
>
>Before posting to alt.security.alarms, check the FAQ
>at http://asa.faq.simsware.com for more information.
>
David Norris
KAREN8927 wrote
>(Where the hell am I and pleas tell me, why does the Greatful Dead keep
>following me all around the country?)
>
David
Robert L Bass
Robert L Bass
>
>how do you guys explain a pir with mirror optics?? example ds-774 or 938,
it
>dosent go through the glass, it reflects off the surface.
Actually, most of the PIR mirror optics I've run across are just plastic
reflectors.
Bob
Frank asked about detection through a window. He then asked about PIRs.
What he wanted was info on detection through a window. Although the ongoing
thread on PIR technology turned out to be quite educational it didn't answer
the question asked.
Reply to:
Bob
The Security Consultant
rob...@digitaldune.net
or ICQ#12280352
electrnpshr wrote in message <360db155...@news.ilnk.com>...
>A good summary of what we learned Robert. Lordy what a long thread ,
>but I think I did learn something.GFK.
>
>On Mon, 28 Sep 1998 23:41:03 GMT, "Robert L Bass" <alar...@Home.com>
>wrote:
>
>>
Joe Paletta
Gentlemen,
I took a coffee table glass top and put it between myself and my PIR.
It detected my arm movment in Front of the glass but not behind it.
I know this is a very unscientific report but it is a start.
Joe Paletta
Preferred Security Systems
Joe Paletta
All due respects,why?, would you post an answer to a question that has
nothing to due with this NG and not E-mail the person?????
Yes I know this question should have been E-mailed to you but maybe you can
correct me or tell the group why. I am missing something?
Joe
David Norris wrote in message <6uo8a1$smi$1...@news1.rmi.net>...
John Durbin
least have spelled the band's name right ...
JD
not a Head but even I've heard that one before
David Norris wrote:
>
> KAREN8927 wrote
> >(Where the hell am I and pleas tell me, why does the Greatful Dead keep
> >following me all around the country?)
> >
> Magnetic personality?
> David
--
remove "end_spam_abuse." to reply
Shaggy
<ld...@idirect.com> wrote:
>
>DepthExplr wrote in message
><19980926171700...@ngol06.aol.com>...
>>
>>ala...@aol.com (ALARMIN) writes:
>>>OK ......... NOW .......... to continue .................
>>> now that we've determined that the infrared energy that our industry
>PIR's
>>>detect cannot easily penitrate glass ................
>>>AND ................
>>>now that we've determined the mirrors can reflect the infrared energy and
>>>trip
>>>a PIR detector ........
>>>Now think about how a mirror is made ....... a piece of glass
>.....silvered
>>>on
>>>the back side .......
>>>How does the infrared energy pass through the mirror glass ...... reflect
>off
>>>of the silvering on the back ....... pass back through the glass and
>activate
>>>the PIR ???????????????
>>
>>Thi IR does not pass through the glass and reflect on the silvering of the
>>mirror, it reflects off the glass surface, it never reaches the sivering
>back.
>>It will reflect the same way on lots of different materials like plastic,
>>metal, coated woods, glossy paper, etc.
>>
>>MT
>
>I find this whole conversation curious, ir going thru glass, reflecting off
>of glass?
>Pir "Passive Infared" Passive meaning it does not send it just looks. I have
>yet to see one that picks up thru glass. When the pir is being used to
>"detect" an "intruder" they usually are on the correct side of the glass.
>Manufactures know this i am sure. Thus, they must take the glass situation
>into account.
>Beams are beams, its a light source and will go thru glass.
Uh, really? Maybe you should do a little research into what "light"
is.
>The lenses on
>the beams act as filters i believe.
Keep up the research. The lenses focus the IR onto the detector.
>Back to PIRs, They look for a change in temperature, hot to cold, cold to
>hot. Now, if you stand in front of a mirror and the sun hits the mirror, you
>will feel the heat of the sun. So will the pir. Shinny surfaces can be a
>problem.
What does this have to do with an infrared motion detector detecting
through glass, Professor?
>I ran into a false alarm situation a couple of years ago that was quite
>interesting. I had a customer who was having cronic false alarms in the
>evening. Seems the sensor had been changed numerous times with no positive
>results. The problem turned out to be a smoldering fireplace. They had put
>out the fire, turned on the alarm and went to bed. Masked the fireplace out
>so Santa could get down, yet he could not steal anything.
A dual tech motion detector would have prevented the problem in the
first place. Sounds like a whole lotta work for nothing, starting
with a poor alarm design.
>Drafts thru the wall where the wiring comes thru can be a problem at times.
>Seal the sensor openings properly.
>Any! light plastics such as used in packing in a factory change temperature
>rapidly when gas heaters come on.
Very interesting. Exactly how fast does the plastic change temp? Is
this fast enough to cause a IR motion detector to trip? Really
Professor, give me detailed facts.
Robert L Bass
>
> "Lawrence Dorsey" wrote:
>>
>> Back to PIRs, They look for a change in temperature, hot to cold, cold to
>> hot. Now, if you stand in front of a mirror and the sun hits the mirror,
you
>> problem.
>
> What does this have to do with an infrared motion detector detecting
> through glass, Professor?
Nothing. But it is true.
>> I ran into a false alarm situation a couple of years ago that was quite
>> interesting. I had a customer who was having cronic false alarms in the
>> evening. Seems the sensor had been changed numerous times with no
positive
>> results. The problem turned out to be a smoldering fireplace. They had
put
>> out the fire, turned on the alarm and went to bed. Masked the fireplace
out
>> so Santa could get down, yet he could not steal anything.
>
> A dual tech motion detector would have prevented the problem in the
> first place. Sounds like a whole lotta work for nothing, starting
> with a poor alarm design.
Actually, simply aiming or masking at the outset would have avoided the
problem. A dual-tech might have been helpful but using it instead of proper
mounting and aiming is not a sign of good design any more than tossing a
grenade in the pond is good fishing.
>> Drafts thru the wall where the wiring comes thru can be a problem at
times.
>> Seal the sensor openings properly.
>> Any light plastics such as used in packing in a factory change
temperature
>> rapidly when gas heaters come on.
>
> Very interesting. Exactly how fast does the plastic change temp? Is
> this fast enough to cause a IR motion detector to trip? Really
> Professor, give me detailed facts.
Many manufacturers of motion detectors support the gentleman's point here.
Some even package a bit of plastic putty with each unit to seal the holes.
It is good practice to seal the wire hole in the sheetrock too. I've
serviced many systems during takeovers where a poorly sealed wall opening
was causing repeated false alarms on a PIR.
>> Now I don't know about the rest of the
>> world but here in Canada we get all kinds of weather and all kinds of
>> strange things happen. Kind of off subject here but i hope this helps
>> someone. Interesting group you people have going here.
Now that you're participating you're part of the group too. Don't let the
sarcastic demeanor of a Few folks bother you either. Your contributions are
quite welcome here.
David Norris
Joe Paletta wrote
>David,
>
>All due respects,why?, would you post an answer to a question that has
>nothing to due with this NG and not E-mail the person?????
Just a little humor. You may have noticed, sometimes
this NG gets a little uptight.
>
>Yes I know this question should have been E-mailed to you but maybe you can
>correct me or tell the group why. I am missing something?
>
>Joe
Another thing that occasionally happens in this NG
(as in many others) is 'off topic' discussion. If my
post has upset you, be assured - such was not
my intent.
David
Shaggy
wrote:
>Shaggy wrote:
Oh, I forgot. You're the god of all alarms. Actually, the Captain of
Bull Shit is more like it. Sure, take a perfectly good motion
detector and poke it's eye out so it can't see the fireplace. Sorry
Captain BS, but THAT'S poor alarm design. Placing a dual tech
detector will allow TOTAL coverage without any blind spots. And it
will, without a doubt prevent false alarms due to the fireplace.
>>> Drafts thru the wall where the wiring comes thru can be a problem at
>times.
>>> Seal the sensor openings properly.
>>> Any light plastics such as used in packing in a factory change
>temperature
>>> rapidly when gas heaters come on.
>>
>> Very interesting. Exactly how fast does the plastic change temp? Is
>> this fast enough to cause a IR motion detector to trip? Really
>> Professor, give me detailed facts.
>
>
>Many manufacturers of motion detectors support the gentleman's point here.
>Some even package a bit of plastic putty with each unit to seal the holes.
>It is good practice to seal the wire hole in the sheetrock too. I've
>serviced many systems during takeovers where a poorly sealed wall opening
>was causing repeated false alarms on a PIR.
Sorry Captain BS, but the gentleman stated that the rise of heat in a
room will cause the plastic housing to change temps rapidly. I wanted
details as to how this causes false alarms.
FYI I agree with sealing all holes in a motion detector of any type,
that's why I carry silicone in my tool pouch.
>
>>> Now I don't know about the rest of the
>>> world but here in Canada we get all kinds of weather and all kinds of
>>> strange things happen. Kind of off subject here but i hope this helps
>>> someone. Interesting group you people have going here.
>
>Now that you're participating you're part of the group too. Don't let the
>sarcastic demeanor of a Few folks bother you either. Your contributions are
>quite welcome here.
>
The original posters comments are quite welcome, but making broad
statements without any details or facts to back them up serve little
purpose.
So I guess I made it off your shit, er kill list. Oooops, I just made
it back on didn't I? <SNICKER>
>Regards,
>Robert
>
<MERCIFUL SNIP OF BORING TAGLINE>
David Norris
Shaggy wrote
> snip <
>Oh, I forgot.
> snip <
>Sorry
> snip <
>it back on didn't I? <SNICKER>
This behavior can be called
many things, _professional_
is not one of 'em.
David
z
>
> Thi IR does not pass through the glass and reflect on the silvering of the
> mirror, it reflects off the glass surface, it never reaches the sivering
back.
> It will reflect the same way on lots of different materials like plastic,
> metal, coated woods, glossy paper, etc.
Hmm. I can't tell you what happens to the portion of the IR band that
strikes a mirror. But I suggest you do a simple experiment with a common
mirror. The lavatory mirror will do just fine.
Place a solid object, like a credit card against the glass. Notice that the
reflected image doesn't abut the object. It appears to be separated by
about 1/4" to 1/2" from the real object. That is because the reflection
occurs at the silvering and not at the first surface of the glass.
Mirrors (glass ones at least) allow visible spectrum light to pass through
them to the silvering on the back. The reflection is not from the primary
surface. If it was, there would not be a need for the silver.
I concur that the portion of the spectrum with which PIRs are concerned
doesn't pass well through glass. But it should be clear that IR energy of
one form or another does pass in sufficient quantity to create problems. So
we are back to the manufacturers' instructions. The conventional wisdom on
the subject is that PIRs are not designed to detect burglars through
windows. However, they can detect problem radiation through glass so they
should not be pointed towards a window.
z
walked into your living room as you pulled that one, friend. <ggg>
Regards,
Robert L Bass
----------------------------
Bass Home Electronics
Online DIY Superstore
http://www.BassHome.com
----------------------------
Joe Paletta
clearer"on her kitchen sink. As I found out our bathroom sink and the
kitchen sink are connected by a common trap (they are separated by a thin
wall). I was brushing my teeth looking at the drain when this high pressure
fountain of muck and mire and God knows what did a perfect split around my
face and ruined just about everything in the bathroom.
I have been known to run around the house in the buff. If she would have
seen me this way looking at a PIR moving my hands.........I'm sure you can
imagine....
To be honest with you I was alone.
Joe Paletta
Preferred Security Systems
P.S. For anyone that tells me I should have E-mailed this to Robert, I'm
sure you are correct, but I thought you all could use a laugh at my expense.
Have a good and profitable day mates ;-)
z wrote in message ...
robert
In response to ir passing through glass. All I have to say is
refraction. Reflected ir energy has very high refraction when striking
glass, thus very little passive ir will pass through. This is different
than when we use a transmitted ir through glass, when ir is transmitted
through glass the whole object is to obtain little refraction from
occuring at the source end. Once the ir is introduced into the glass it
travels quite easily. At the other end of lets say fiber is where
signal is reduced (db loss) . From refraction. In other words
resistance to penetrate out. That is why its so important to have a 90
degree cleave. The main thing is reflected light v.s. transmitted.
Robert//Action Alarm Systems//Hawaii
Shaggy431
wrote:
BLAH, BLAH, BLAH, YADDA, YADDA, YADDA
Your opinion REALLY matters to me, in fact so much that zzzzzzZZZZZ
>
David Norris
Shaggy431 wrote
>
>BLAH, BLAH, BLAH, YADDA, YADDA, YADDA
>
>Your opinion REALLY matters to me, in fact so much that zzzzzzZZZZZ
If my opinion did not matter, you
would not bother to respond.
The point, which you appear to
have missed, is that your
arguments, whatever their value,
are not enhanced by personal
attacks.
David