Monitoring and outputs
Reference Manual
June 2016
MAN-0076, Revision 09
30
Monitoring and outputs
Figure 6-1 Analog/HART wiring
6.3
Relays (Optional)
Optional electromechanical relays have Form-C SPDT contacts rated 5 Amps at 30 VDC/ 250 VAC.
There are four physical relays; one Fault and three Alarm relays. These relays have Normally Open and
Normally Closed contacts at the output terminals.
6.3.1
Alarm relay(s)
The Millennium II transmitters can be ordered with three (3) programmable alarm relays. These relays
will change state from their non-alarm state to an alarm state when gas concentrations, as read by the
sensor, reach the programmed alarm points set in the transmitter.
The alarm relays can be programmed to change states on alarm point #1 or alarm point #2 for either
channel. They can also be programmed to be energized or de-energized under normal conditions, and
then either latching or non-latching.
6.3.2
Fault relay
Millennium II transmitters and sensors complete continual checks for situations that may prevent the
transmitter and sensor from providing an expected response to ambient conditions and records these
as a fault condition in the message log and the output(s) of the transmitter. When a system fault is
detected, the Red Status LED will flash fast (250 milliseconds on, 250 milliseconds off), the analog
output will output a 2.5
mA signal, and the fault relay will change states (de-energize to provide a fault
condition).