Emerson Rosemount 644, Reference Manual

Page: 39 / 182

29
Reference Manual
00809-0200-4728, Rev RA
Section 2: Configuration
April 2015
Configuration
2.8.3 Configure alarm and saturation levels
In normal operation, the transmitter will drive the output in response to measurements
between the lower to upper saturation points. If the temperature goes outside the sensor limits,
or if the output would be beyond the saturation points, the output will be limited to the
associated saturation point.
The 644 transmitter automatically and continuously performs self-diagnostic routines. If the
self-diagnostic routines detect a failure, the transmitter drives the output to configured alarm
value based on the position of the alarm switch. The Alarm and Saturation settings allow the
alarm settings (Hi or Low) and saturation values to be viewed and changed.
Failure mode alarm and saturation levels can be configured using a Field Communicator, AMS
Device Manager, and the LOI. The following limitations exist for custom levels:

The low alarm value must be less than the Low Saturation level.

The high alarm value must be higher than the High Saturation level.

Alarm and Saturation levels must be separated by at least 0.1 mA
The configuration tool will provide an error message if the configuration rule is violated.
See Table 2-4 , Table 2-5 , and Table 2-6 below for the common Alarm and Saturation levels.
Note
Transmitters set to HART multi-drop mode send all saturation and alarm information digitally;
saturation and alarm conditions will not affect the analog output.
Table 2-4. Rosemount Alarm and Saturation Values
Level 4–20 mA saturation 4–20 mA alarm
Low 3.9 mA
≤
3.75 mA
High 20.5 mA
≥
21.75 mA
Table 2-5. NAMUR-Compliant Alarm and Saturation Values
Level 4–20 mA saturation 4–20 mA alarm
Low 3.8 mA
≤
3.6 mA
High 20.5 mA
≥
22.5 mA
Table 2-6. Custom Alarm and Saturation Values
Level 4–20 mA saturation 4–20 mA alarm
Low 3.7 mA - 3.9 mA 3.6 mA - 3.8 mA
High 20.1 mA - 22.9 mA 20.2 mA - 23.0 mA