Spectrex Quasar 900 Open-Path Gas Detection System - Manual (Page 25)

Operational Modes 13
3 Operating Modes
➣ In this chapter…
Operational Modes page 13
Visual Indicators page 15
Output Signals page 15
System Setup page 16
3.1 Operational Modes
The Quasar 900 has four operational modes:
 Normal Mode, page 13
 Maintenance Call Mode (3mA Output), page 13
 Fault Mode, page 14
 Zero Calibration Mode (1mA Output), page 14
3.1.1 Normal Mode
This mode is used for gas detection. In normal mode, the following statuses
are possible:
 Normal - Signal received from gas detection is at safe levels.
 Warning* - Gases have been detected at warning levels.
 Alarm* - Gases have been detected at alarm levels.
Note: For the standard 0-20mA output, the Warning and Alarm levels are
not relevant. The user chooses these alarm levels at the controller. The
output Detector will be 4mA at zero reading and 20mA for full-scale reading.
Warning and Alarm states are relevant where the stepped 0-20mA output is
used and will energize the warning and alarm relays.
If the RS485 output is used, the Detector changes its status from ‘N’ to ‘W’
at Warning level and to ‘A’ at Alarm.
3.1.2 Maintenance Call Mode (3mA Output)
This mode indicates low signal or low signal ratio that may be caused by a
dirty window; misalignment; poor source or that one of the Detectors
parameters is at the ‘limit’ value.
The Detector continues to function and reads any gas present, but provides
a (3mA) pre-warning signal that a maintenance procedure is required.