Bosch DS422I User Manual download pdf (Page 4)

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03/04

DS422i/DS426i Installation Instructions

P/N: 44974D Page 4

Figure R- Perimeter protection

Note that the beams are mounted so they cross each other. This way,

an intruder can not enter the area by walking between the units.

When installing multiple transmitters and receivers, test with all the

receivers powered-up, but with only one transmitter powered-up at a

time. A transmitter should set up only its receiver.

Receivers physically too close to a different system’s transmitters

may be set up even if the transmitter is not pointed at them (see

Figure T).

Figure T - Close proximity field problem

If a receiver is being set up by the wrong transmitter, the signals can

usually be eliminated by masking the sides of the transmitter and

receiver. Use electrician’s tape or duct tape inside each enclosure’s

window.

When installing these systems, remember that the infrared signal may

reflect off objects (e.g. glossy walls or floors) in the coverage area and

still set up the receiver.

A thorough walk test performed at several different points within the

coverage area will catch this problem. Re-aligning the units should

solve this problem.

The only way to insure proper continual protection is to perform

regular walk tests of the desired coverage area.

9.0 Application Tips

When using photoelectric detectors for motion detection, there are a

few installation techniques that will make the system more versatile.

9.1 Beam Stacking

Beam stacking gives a wall

of protection by stacking

several units at different

heights and providing an

alarm activation on the

blockage of only one pair of

beams (see Figure N for the

correct set-up technique).

Note that the system is

installed with alternating

transmitters and receivers at

each end. This eliminates the

possibility of a receiver being

covered by more than one

transmitter.

The maximum spacing between receivers (S) can be calculated by

dividing the distance between the transmitter and its receivers (D) by

20.

Therefore, if the distance between a transmitter and receiver is 100

ft. (30 m), the maximum spacing between receivers would be 100 ft.

(30 m) ÷ 20, or 5 ft. (1.5 m)

S = D/20 S = 100 ft. (30 m)/20 S = 5 ft. (1.5 m)

A potential problem when installing systems in a beam stack is “Near

Field Reflection.” Near field reflection is caused when a reflective

object is placed in the line-of-sight of the detectors and causes the

transmitted signal to be reflected to the wrong receiver (see Figure

P).

Figure P - Near field reflection

It may be desirable to have more than two sets of beams to create

taller stacks. This can be accomplished by adding receivers as shown

in Figure Q). Note that the beam from each transmitter is covering

two receivers.

Figure Q - Multi-system stack

9.2 Perimeter Protection

When protecting the interior of an installation, a good technique is to

mount the units at 90° angles around the coverage area (see Figure

R).

Figure N - Beam stack method

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