Detcon TP-624D - Manual (Page 8)

Model TP-624D
TP-624D Instruction Manual Rev. 0.4 Page 4 of 40
1.3 Relay Outputs
The TP-624D includes three 5A Form C relay outputs. Two of these relays are dedicated to alarm outputs, and
the third is used to indicate when the sensor is in fault. The common and normally closed contacts on the alarm
relays are connected when the gas concentration is below the alarm threshold. If the concentration exceeds the
alarm threshold for more than five seconds, then the common and normally open contacts will be connected.
The common and normally closed contacts on the fault relay are connected when the sensor is not in fault. If
the sensor experiences a fault condition for more than five seconds, then the common and normally open
contacts will be connected.
The common and either the normally open or the normally closed contacts from the alarm and fault relays are
connected to terminals on the base connector board. A jumper near each relay is used to select whether the
normally open or normally closed contact is connected to the terminal on the base connector board.
The relays can be configured to operate in Energized Mode. In this mode, the common and normally open
contacts are connected when the gas is below the alarm threshold (alarm relays) or is not in fault (fault relay).
This mode allows for fail-safe operation of the sensor. If the power to the sensor fails or the cable to the sensor
I/O is disconnected, then the common and normally open contacts will no longer be connected.
The alarm and fault relays can be configured as either latching or non-latching. In non-latching mode, the relay
is deactivated as soon as the sensor alarm or fault condition is cleared. In latching mode, the relay remains
active even after the alarm or fault condition has cleared. Once activated, the relay can only be deactivated by
swiping a magnetic programming tool above the PGM1 or PGM2 mark on the TP-624D face plate.
The alarm relays can be configured for ascending or descending mode. In ascending mode the relay will be
activated when the concentration is above the alarm threshold. This is the most common mode of operation for
the TP-624D. The alarm relays can also be activated in descending mode. In this mode, the alarm relays will
activate when the concentration is below the alarm threshold.
NOTE: The relay outputs will not activate during the first 60 seconds after sensor power up.
This allows the sensor cell to stabilize and begin outputting an accurate reading.