Emerson Rosemount 975HR, Reference Manual

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• Alarm latch: No
• Auxiliary relay: No
• Automatic BIT: Yes
• Alarm BIT: No
• Auxiliary BIT: No
• Heated optics: Auto
• Temperature: 41 °F (5 °C)
2.8.1 Sensitivity
The detector offers four sensitivity settings. The settings refer to an n-heptane or gasoline
fire of 1 ft.
2
(0.1 m
2
), from the low sensitivity of 50 ft. (15 m) to 215 ft. (65 m).
For other types of fuel sensitivity, refer to Table 1-2 .
2.8.2 Alarm delay
The flame detector is equipped with an alarm delay option, which provides programmable
time delay with settings at:
• Antiflare
(1)
(default)
Other delay settings are available:
• 0, 3, 5, 10, 15, 20, or 30 seconds
When an alarm (detection) level condition occurs, the flame detector delays the execution
of the alarm outputs by the specified period of time. The detector then evaluates the
condition for three seconds. If the alarm level is still present, the detector activates the
alarm outputs. If this condition no longer exists, the detector returns to its standby state.
The alarm delay option affects the output relays and the 0-20 mA output. The LEDs and
outputs indicate warning levels during the delay time only if the fire condition exists.
2.8.3 Address setup
The flame detector provides up to 247 addresses that can be changed with the RS-485
communication link or the HART
® communication protocol.
2.8.4 Function setup
You can select the desired functions as detailed in Table 2-3 .
(1) The Antiflare mode is selected to prevent false alarms in locations where fast flares may be present. The time delay for fire
alarms in this mode ranges from 2.5 to 15 seconds (usually less than 10 seconds).
Installing the detector Reference Manual
June 2021 00809-0100-4976
40 Emerson.com/Rosemount
Legacy