ProtEX PD8-6080/PD8-6081 Explosion-Proof Modbus
®
Scanner Instruction Manual
51
Signal Loss or Loop Break Relay Operation
The following graph shows the loop break relay operation for a high alarm relay.
When the scanner detects a break in the 4-20 mA loop, the relay will go to one of the following selected
actions:
1. Turn
On
(Go to alarm condition)
2. Turn
Off
(Go to non-alarm condition)
3. No action (
no Act
) (Processed as a low signal condition)
Time Delay Operation
The following graphs show the operation of the time delay function.
When the signal crosses the set point, the
On
time delay timer starts and the relay trips when the time delay
has elapsed. If the signal drops below the set point (high alarm) before the time delay has elapsed, the
On
time delay timer resets and the relay does not change state. The same principle applies to the
Off
time
delay.
Note: If
“
Automatic or Manual
(
A-mAn
)”
reset mode is selected, the LED follows the reset point and not
the relay state when the relay is acknowledged.
Relay
LED
Input
Loop Break = Ignore
de-energized
energized
off
on
Relay
LED
Loop Break = Off
Relay
LED
Loop Break = On
Set
Reset
