4 How to Use
4-3. Precautions for system designing
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(4) Alarm contact
The alarm contact of the alarm system is used to transmit signals to activate an external buzzer or alarm
lamp. Do not use the alarm system for controlling purpose (e.g., controlling the shutdown valve).
The specifications for the alarm contact of the alarm system are based on the resistance load conditions. If
inductive load is used at the alarm contact, the following errors will occur easily because counter
electromotive voltage is generated at the contact.
Deposition, defective insulation or defective contact at the relay contact
Damage of any electric parts due to high-voltage generated inside the alarm system
Abnormal operations by an out-of-control CPU
Unexpected noise may enter the contact regardless of inductive load, thus posing a risk of above
errors.
* Followings are examples of inductive load.
Revolving light, external relay, buzzer, siren, fan, fluorescent lamp, motor, etc.
If load is to be activated, appropriate measures must be taken to stabilize the operation of the alarm system
and protect the alarm contact referring to the following information.
Relay it with an external relay at a lower voltage of 100 VAC or below (contact amplification). At
the same time, the surge absorbing part SK1 suitable for the specifications must be attached to
the external relay.
In addition, the surge absorbing part SK2 must be attached to the loaded side of the external
relay if necessary.
It may be recommended that the surge absorbing part should be attached to the contact for
certain load conditions. It must be attached to an appropriate position by checking how the load
is activated.
CAUTION
The "b" contact (break contact) under de-energized state may be opened momentarily by a physical
shock, such as external force.
When the "b" contact is selected for the alarm contact, take appropriate actions to prepare for a
momentary activation, for example, add signal delay operation (approximately 1-second) to the
receiving side of the "b" contact.
CAUTION
In principle, do not activate inductive load at the alarm contact of the alarm system. (In
particular, never use the inductive load to activate a fluorescent lamp, motor, etc.)
If inductive load is activated, relay it with an external relay (contact amplification). However,
because the coil of an external relay also involves inductive load, select a relay at a lower
voltage (100 VAC or below), and then protect the contact of the alarm system with an
appropriate surge absorbing part, such as a CR circuit.
