Re: Help on alarm

[JoeRaisin <joeraisin@xxxxxxxxxxx>]

Jim wrote:

> JoeRaisin wrote:
>
>>>
>>>Joe, are you recommending dual tec's in this configuration or just
>>>PIR's?
>>>
>>>I wouldn't ...... unless the mfg of the dual-tec's have designed the
>>>units to be used in close proximity to one another.
>>>
>>
>>Not real familiar with Paradox, but I think they are PIR's.
>>But my layout was with dual tech's in mind.
>>A single unit at location *1 or dual units, one at the * in the upper
>>left hand corner and one at location *2 would avoid the units seeing
>>each other.
>
>
> Hi Joe,
>
> If I'm seeing it right in your drawing, the "array" of each unit will
> still be in view of each other. The units don't actually have to be in
> "sight" of each other. It's the beat frequency of the slightly
> different outputs of each unit that will cause, what looks like a
> doppler shift to either or both of the units, that will cause the false
> alarms. With some manufacturers, they don't recommend that units be
> within "range" of each other ( ie you must consider penetration of
> walls etc) nor do they recommend units be mounted "back to back"
> either. It's the "arrays" overlapping each other, even if they're not
> within in the line of sight, that can cause the problems. And, for
> example, you have to keep in mind that even in large areas like
> warehouses, with, we'll say 2 units with 35 foot range, they *still*
> should not be looking at one another closer than ..... say 90 feet or
> more. Just because a unit is rated at 35 feet doesn't mean that it's
> microwave array doesn't extend further. It just means that the unit can
> detect movement of a body at that distance. The array can extend much
> further than that.
>
Which is why you adjust the microwave sensitivity down to the minimum
need for the application.  I would be confident in the layout I proposed.
But let me restate that I would prefer the single unit at the *1 location.
Only if he really needs that small area at the bottom protected would I
go to the double unit arrangement.
As I look at the drawing the two corners appear to overlap so the units
won't see each other.  If you can see past the corners (from the upper
left to the lower right then a single unit in the upper left or lower
right may do or move the lower unit to the left side of that area.