Table of Contents
Advertisement
Reference Manual
00809-0100-4036
3
Operating modes
3.1
Operational modes
The Rosemount 936 has four operational modes:
•
Normal mode
•
Maintenance call mode (3 mA output)
•
Fault mode
•
Zero calibration mode (1 mA output)
3.1.1
Normal mode
This mode is used for gas detection. In Normal mode, the following statuses are possible:
•
Normal (N): Signal received from gas detection is at safe levels.
•
Warning (W): Gases have been detected at warning levels.
•
Alarm (A): Gases have been detected at alarm levels.
NOTICE
For the standard 0-20 mA output, the warning and alarm levels are not relevant. Choose
these alarm levels at the controller. The output detector is at 4 mA at zero reading and 20
mA for full-scale reading.
If using the RS-485 output, the detector changes its status from N to W at Warning level
and to A at Alarm level.
3.1.2
Maintenance call mode (3 mA output)
This mode indicates low signal that may be caused by a dirty window, misalignment, or
poor source or if one of the detector's parameters is at the limit value.
The detector continues to function, but provides a (3 mA) pre-warning signal (via HART
and Modbus
3.1.3
Fault mode
In the fault status, there are three fault types.
•
Fault 1 (2 mA output) - non-critical
If this occurs, it is due to blockage, very low signal, partial obscuration, or full beam
block. In this situation, detection is no longer possible. The detector's proper operation
can be restored (auto reset) during operation if the condition causing the problem is
removed or resolved. This mode occurs after a delay of 60 seconds from the moment
of the fault. This delay is important to eliminate momentary obscuration due to
passing through the beam.
Rosemount 936
®
) that a maintenance procedure is required.
Operating modes
October 2021
®
19
Advertisement
Table of Contents
