Helios Large Display Dual Analog Input Rate/Totalizer Instruction Manual
PD2-6262
38
Setting Fail-Safe Operation
In fail-safe mode of operation, the relay coil is energized when the process variable is within safe limits
and the relay coil is de-energized when the alarm condition exists. The fail-safe operation is set
independently for each relay. Select
on
to enable or select
off
to disable fail-safe operation.
Programming Time Delay
The
On
and
Off
time delays may be programmed for each relay between 0 and 999.9 seconds. The
relays will transfer only after the condition has been maintained for the corresponding time delay.
The
On
time delay is associated with the set point.
The
Off
time delay is associated with the reset point.
Relay Action for Loss of 4-20 mA Input (Loop Break)
The loop break feature is associated with the 4-20 mA input. Each relay may be programmed to go to one
of the following conditions when the meter detects the loss of the input signal (i.e. < 0.005 mA):
1. Turn
On
(Go to alarm condition)
2. Turn
Off
(Go to non-alarm condition)
3. Ignore (Processed as a low signal condition)
Note: This is not a true loop break condition; if the signal drops below 0.005 mA, it is interpreted as a
“loop break” condition.
Relay and Alarm Operation Diagrams
The following graphs illustrate the operation of the relays, status LEDs, and ACK button.
High Alarm Operation (Set > Reset)
For Manual reset mode, ACK can be pressed
anytime to turn "off" relay. To detect a new alarm
condition, the signal must go below the set point,
and then go above it.
Low Alarm Operation (Set < Reset)
For Manual reset mode, ACK can be pressed
anytime to turn "off" relay. For relay to turn back
“on”, signal must go above set point and then go
below it.
