ProtEX-MAX PD8-7000 Explosion-Proof Temperature Meter Instruction Manual
36
Latching and Non-Latching Relay Operation
The relays can be set up for latching (manual reset) or
non-latching (automatic reset) operation.
The On and Off terminology does not refer to the status of
the relay’s coil, which depends on the fail-safe mode
selected.
Warning!
In latching relay mode, latched relays will reset
(unlatch) when power is cycled.
Non-Latching Relay (
Auto
)
In this application, the meter is set up for automatic reset
(non-latching relay). Acknowledging the alarm while it is still
present has no effect on either the LED or the relay. When
the alarm finally goes away, the relay automatically resets
and the LED also goes off.
Non-Latching Relay (
A-nman
)
In this application, the meter is set up for automatic and
manual reset at any time (non-latching relay). The LED and
the relay automatically reset when the meter returns to the
normal condition.
The next time an alarm occurs, the operator acknowledges
the alarm manually while the alarm condition still exists.
This causes the relay to reset, but the LED stays on until
the meter returns to the normal condition.
Latching Relay (
LatcH
)
In this application, the meter is set up for manual reset at any
time. Acknowledging the alarm even if the alarm condition is
still present resets the relay and turns off the LED.
Latching Relay (
Lt-Clr
)
In this application, the meter is set up for manual reset only
after the signal passes the reset point (alarm condition has
cleared). Acknowledging the alarm while it is still present has
no effect on either the LED or the relay. When the alarm is
acknowledged after it returns to the normal state, the LED
and the relay go off. Notice that the LED remains on, even
after the meter returns to the normal condition. This is
because, for latching relays, the alarm LED reflects the
status of the relay, regardless of the alarm condition.
Relay terminology for following tables
Terminology
Relay Condition
On
Alarm (Tripped)
Off
Normal (Reset)
Ack
Acknowledged
Automatic reset only
Condition
LED
Relay
Normal
Off
Off
Alarm
On
On
Ack (No effect)
On
On
Normal
Off
Off
Aut manual reset at any time
Condition
LED
Relay
Normal
Off
Off
Alarm
On
On
Normal
Off
Off
Next Alarm
On
On
Ack
On
Off
Normal
Off
Off
Manual reset any time
Condition
LED
Relay
Normal
Off
Off
Alarm
On
On
Ack
Off
Off
Manual reset only after alarm
condition has cleared
Condition
LED
Relay
Normal
Off
Off
Alarm
On
On
Ack (No effect)
On
On
Normal
On
On
Ack
Off
Off
