4. How to Use
4-3. Precautions for system designing
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Do not install the detector head in machinery which is not properly grounded.
Before installing the detector head in machinery, the machinery must be grounded properly.
Do not install the detector head in a place where interference gases exist around it.
The detector head must not be installed in a place where interference gases exist around it.
4-3. Precautions for system designing
CAUTION
An unstable power supply and noise may cause malfunctions or false alarms.
The descriptions in this section must be reflected on the designing of a system using the detector
head.
Using a stable power supply
The external output and alarm contact of the detector head may be activated when the power is turned on,
when momentary blackout occurs, or while the system is being stabilized. In such cases, use a UPS
(uninterruptible power system), or take appropriate actions on the receiving side.
The detector head must be provided with the following power supply.
Power supply
voltage
15 - 27 VDC (terminal voltage of the main unit)
Allowed time of
momentary blackout
Approx. 1 msec. (To recover from the
momentary blackout for 1 msec. or
more, restart the detector head.)
Example of actions
To ensure continuous operation and
activation, install a UPS, etc. outside
the detector head.
Others
Do not use it with a power supply of
large power load or high-frequency
noise.
Example of actions
Use a line filter, etc. to avoid the noise
source if necessary.
Heat radiation designing
When the alarm system is installed in a closed instrumentation panel or the like, attach ventilation fans
above and below the panel.
Introducing protective measures against lightning
If cables are installed outside the factory/plant, or if internal cables are installed in the same duct as the
cables coming from outside the factory/plant, "lightning" will cause problems. Because lightning acts as a
large emission source while cables act as a receiving antenna, devices connected to the cables may be
damaged.
Lightning cannot be prevented. Cables installed in a metal conduit or under the ground cannot be
completely protected from inductive lightning surge caused by lightning. Although complete elimination of
disasters caused by lightning is impossible, the following protective measures can be taken.
Protection against
lightning
Take appropriate measures in accordance with the importance of the facilities and
the environment.
Provide protection by a lightning arrester (cable arrester).
(Although inductive lightning surge can be transmitted through the cable, it
is prevented by installing a lightning arrester before the field devices and
central processing equipment. For information on how to use a lightning
arrester, please contact the manufacturer.)
Grounding
In addition to lightning, there are more sources of surge noise. To protect units
from these noise sources, the units must be grounded.
* The lightning arrester has a circuit to remove a surge voltage which damages field devices, so that
signals may be attenuated.
Before installing a lightning arrester, verify that it works properly.
