
Chapter 3 _______________________________________________________________ Installation
VAISALA _______________________________________________________________________ 61
Selecting the Activation State of the Relay
The middlemost C terminal and either one of the terminals NO/NC shall
be connected. The polarity can be freely selected.
NO Normally open
C Common relay
NC Normally closed
Relay NOT activated: C and NC outputs are closed, NO is open
Relay IS activated: C and NO outputs are closed, NC is open.
Connect the power and close the cover. For instructions on how to
operate the relay (for example, select quantity for the relay output and set
the relay setpoints) see section Operation of Relays on page 120.
0503-037
Figure 40 Relay Module
Numbers refer to Figure 40 above:
1 = Indication led for the relay 1 or 3
2 = Relay test buttons
3 = Flat cable pins
4 = Indication led for relay 2 or 4
WARNING
The relay module may contain dangerous voltages even if the
transmitter power has been disconnected. Before working on the relay
module you must switch off both the transmitter and the voltage
connected to the relay terminals.
WARNING
Do not connect the mains power to relay unit without grounding the
transmitter.
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