Pir Positioning / Windows - Room Plan

[p-j-smith]

Hi All

I'm going to do a home install shortly, been planning for few weeks and now have my system purchase ready.

Going for a Texecom Premier 48, will also be using the grade 3 anti masking PIR that Texecom offer (Prestige)

Sorry for what may be a basic question, but the install manuals say the sensor should not look at a window, (other info on line says PIR's should not look at windows within 1/2 of there range).

Should the sensors therefore point away from windows, or are they OK at a 45 degree angle.

I've attached a floor plan to my home (hope this works), for ref the rooms A & B are approx 4m square. The N/S/E/W is just for ref is needed for position description.

From this, is there an optium position to where the sensors should go, I'm planning of 1 in each of the 4 rooms.

Rooms A & D get the sunrise, when the miday / evening sun moves around to the side of the house where there are no windows on the ground floor.

I was thing the sensors should see the windows as thats where someone would break in, but is this not the case and should I be looking away from the windows hence the alarm will only activate when someone is well inside the room?

Thanks in advance.

Peter

[DirectFS]

Hi All

"Should the sensors therefore point away from windows, or are they OK at a 45 degree angle."

It isn't generally a good idea to point infrared detection at windows because glass is a surface which is subject to rapid temperature change - as is the metal on a radiator. However, most detectors on the market these days will provide a degree of forgiveness for this type of thing.

It helps to have an understanding of what a PIR is, what it detects, and hence, how it works. Firstly, it is important to know that it DOES NOT detect motion. It is incorrect to call a PIR a movement, or motion detector - that, strictly, would be a microwave detector, or at a push an ultrasonic (which also technically is not a movement detector).

What a PIR does is to detect change in infrared energy levels, across a preset pattern. For this reason, detectors really need to be set at an angle to whatever area you wish to detect change in - rather than directly at the area. This is why you would mostly see detectors mounted in corners. Naturally, humans emit infrared energy, as do all living things. That's what is being detected when intrusion occurs. It's also why pets can set off many types of PIR.

I've attached a floor plan to my home (hope this works), for ref the rooms A & B are approx 4m square. The N/S/E/W is just for ref is needed for position description.

From this, is there an optium position to where the sensors should go, I'm planning of 1 in each of the 4 rooms.

There is an optimum place for every detector, in every case - often false alarms are simply created by utilising the wrong choice of detector. However, I'd suggest that for room A, you'd be best advised to put your PIR above the door, in the SW corner, facing roughly the bookshelf of the opposite wall. If you suffer false alarms at all, consider using the pulse count setting on the unit.

For room D - again, above the door, looking toward the south should be adequate.

I was thing the sensors should see the windows as thats where someone would break in, but is this not the case and should I be looking away from the windows hence the alarm will only activate when someone is well inside the room?

Thanks in advance.

Peter

There's that misconception again - yes, the window is a likely entry point, but no, for the reasons above, you don't want to point it directly at the window.

And the other part of the misconception, or at least misunderstanding - PIRS are called space protection for a good reason - they protect spaces - not perimeters. You'd be looking at something like a seismic impact detector (inertia sensor), such as a Viper, or similar if you wanted perimeter detection.

Bill.

[p-j-smith]

Thanks for the detailed reply Bill.

[NitroN]

Everything above -273 degrees Celcius or 0 degrees Kelvin emmits infra-red energy....

Its all about atoms...

Without going into detail on an open forum, your design theory has errors.

Sorry I cannot explain more, but criminals, despite popular belief can also read.

n