6
Design
36
Bosch Security Systems
Seismic Detectors Application Guide
I-200153-1
04.2016
6.1.3
Calculating the number of detectors required – Example 3
This installation utilizes ISN-SM-90 detectors on a concrete wall.
Radius
(m)
Distances
Calculated
Length (m)
Recommended
Distances
Recommended
Length (m)
Total
Detectors
2.5
d1
2
d1
2
2.5
sd
3.75
sd
3
2.5
sd
3.75
sd
3
2.5
sd
3.75
sd
3
2.5
d2
2
sd
3
d2
2
5
Table 6-3: Wall design - 2.5m detection radius
Figure 6-8 shows the calculated
sd
,
d1
&
d2
distances.
In this example, the calculation using the
d1
and the
sd
does not provide full detection coverage
using four detectors and so a fifth detector is required to provide coverage.
Figure 6-8: Example 3 - inadequate coverage
Figure 6-9: Example 3 - detector spacing with balanced coverage shows the recommended detec-
tor spacing. This example uses 5 detectors, keeping the
d1
&
d2
as per the calculated distance but
decreasing the
sd
to provide balanced coverage.
To balance a system design, the distances
d1
,
d2
&
sd
may be reduced but never in-
creased.
Figure 6-9: Example 3 - detector spacing with balanced coverage
