Detcon 840 - Manual (Page 6)

840 Operators Manual
Model 840 Operator Manual Rev. 1.9 Page 2 of 29
2.
System Operation
The Model 840-N4X can be configured for either eight 4-20mA sensor inputs or eight RS-485 serial sensor
inputs via a dipswitch selection. The system displays current status information on its LCD display. The
information displayed during normal operation includes the gas channel #, current reading and gas type.
Alarm values or fault condition can be field-programmed via the User Interface to cause an assigned relay
output to fire, thus triggering an external alarm device. As gas alarm or fault conditions clear, the assigned
relay outputs return to their normal states. Relays can be set-up as Energized/De-Energized, Latching/Non-
latching and Silenceable /Non-Silenceable. Using the front panel function key, the relay outputs can be
silenced or Reset.
The Model 840-N4X gas detection alarm system has onboard data logging to record all alarm, fault and
maintenance events. It also continuously logs the TWA and Peak readings, which can be downloaded for
external storage and review. The RS-485 serial output can continuously transmit sensor and alarm data to a
PC, PLC, DCS or SCADA where it can be further monitored and logged.
Figure 1 System Operational Diagram
RS- 485 Output
to Master
Device
RS-485
Gas
Sensor
Inputs
4-20mA
Gas
Sensor
Inputs
PROG
↑ ↓
ENTER
ALM 1 ALM 2 ALM 3 FAULT
CH1 99 PPM CL2 CH5 99 PPM CL2
CH2 99 PPM CL2 CH6 99 PPM CL2
CH3 99 PPM CL2 CH7 99 PPM CL2
CH4 99 PPM CL2 CH8 99 PPM CL2
RS-232 Port for
Uploading
Configuration and
Downloading
Historical Data
Input Power
115/230VAC
11.5-30VDC
FAULT RELAY
(2 Discrete
Contacts each)
ALM 3 RELAY
ALM 2 RELAY
ALM 1 RELAY
MODEL 840-N4X
Gas Detection/Alarm System