66
Technical Manual
|
Dräger Polytron
®
8000 Series
Instrument settings
Relay contact Normally Closed (NC) and configuration Normally Energized
The alarm indicator is connected to the Normally Closed relay contact. The relay is
energized during operation and connects the Common terminal with the Normally
Open contact. The electric circuit is open and no current flows to the alarm
indicator.
If an alarm is triggered, the relay de-energizes and the alarm indicator is active.
This setting is suitable for horns and strobes.
Failures such as field wiring faults and defective alarm indicators are not indicated.
Power loss to the transmitter is indicated.
Fig. 19
Example for relay configuration Normally Energized and Normally Closed
relay contact.
Relay contact Normally Closed (NC) and configuration Energized on alarm
The alarm indicator is connected to the Normally Closed relay contact. The relay is
de-energized during operation and connects the Common terminal with the
Normally Closed contact. The electric circuit is closed and the alarm indicator is
active.
If an alarm is triggered, the relay energizes and the alarm indicator is deactivated.
This setting is suitable for green status lights.
Failures such as field wiring faults and defective alarm indicators are indicated.
Power loss to the transmitter is not indicated.
Fig. 20
Example for relay configuration Energized on alarm and Normally Closed
relay contact.
Dräger standard for relay wiring is Normally Open with relay configuration normally
energized. This way, power loss to the transmitter and transmitter-specific failures
are indicated.
36575
3657
6
NC
NO
COM
coil -
coil +
Energized
De-energized, alarm triggerd
NC
NO
COM
coil -
coil +
NC
NO
COM
coil -
coil +
De-energized
Energized, alarm triggerd
NC
NO
COM
coil -
coil +