4. How to Install Gas Monitor
4-2. Precautions for system designing
13
Proper use of alarm contact
The alarm contact of the monitor is used to transmit signals to activate an external buzzer, alarm lamp or
rotating lamp. Do not use it for controlling purpose (e.g., controlling the shutdown valve).
The specifications for the external output gas alarm contact of the monitor 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 force 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 monitor
- Abnormal operations by an out-of-control CPU
If load is to be activated, appropriate measures must be taken to stabilize the operation of the monitor 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 one second) to the
receiving side of the b contact.
GM-600
CAUTION
In principle, do not activate inductive load at the alarm contact of the monitor. In particular, never
use the inductive load to activate a fluorescent lamp or motor.
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 monitor with an appropriate surge
absorbing part, such as a CR circuit.
Alarm contact
Co
il
Power
supply
Power
supply
Load
*SK1, SK2: Surge absorbing part
External relay
(Lower voltage relay)
