Emerson Rosemount 935, Справочное руководство

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3 Operating modes
3.1 Operational modes
The Rosemount 935 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.
View warning and alarm states through the LED, RS-485, and HART
®
.
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 device continues to function, but provides a (3 mA) pre-warning signal (via HART
®
and
Modbus
®
) that a maintenance procedure is required.
3.1.3 Fault mode
In the fault status, there are three fault types.
In all fault types, the LED flashes yellow at 4 Hz.
• Misalignment (2.5 mA) - non-critical
This occurs due to poor alignment. Detection is no longer possible.
• Fault 1 (2 mA output) - non-critical
Reference Manual Operating modes
00809-0100-4035 May 2022
Rosemount 935 17