4 How to Use
4-3. Precautions for system designing
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Do not install the detector in a place where maintenance of the detector cannot be performed or where
handling the detector involves dangers.
Regular maintenance of the detector must be performed.
Do not install the detector in a place where the machinery must be stopped when maintenance is performed
in its inside, where parts of the machinery must be removed to perform maintenance, or where the detector
cannot be removed because tubes or racks prevent access to it. Do not install the detector in a place where
maintenance involves dangers, for example, near a high-voltage cable.
Do not install the detector in machinery which is not properly grounded.
Before installing the detector in machinery, the machinery must be grounded properly.
Do not install the detector in a place where other gases exist around it.
The detector must not be installed in a place where other gases exist around it.
4-3. Precautions for system designing
Using a stable power supply
The external output and alarm contact of the detector may be activated when the power is turned on, when
momentary blackout occurs, or when the system is being stabilized. In such cases, use a UPS, or take
appropriate actions on the receiving side of output signals.
The detector must be provided with the following power supply.
Power supply
voltage
24 VDC±10%: Terminal voltage of the detector
Allowed time of
momentary blackout
Up to 10 milliseconds
(To recover from the momentary
blackout for 10 milliseconds or more,
restart the detector.)
Example of actions
To ensure continuous operation and
activation, install a UPS outside the
detector.
Others
Do not use it with a power supply of
large power load or high-frequency
noise.
Example of actions
Use a line filter to avoid the noise
source if necessary.
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 safety retainer).
(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.
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.
