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Reference Manual
00809-0400-4728, Rev AA
June 2011
Rosemount 644
3-12
AI2 as Terminal Temperature
1. Put the AI Block into OOS mode.
a. Go to MODE_BLK.TARGET
b. Choose OOS (0x80)
2. Go to CHANNEL
a. Choose Body Temperature
3. Go to L_TYPE
a. Choose Direct
4. Go to XD_Scale
a. Choose UNITS_INDEX to be °C
5. Go to OUT_SCALE
a. Choose UNITS_INDEX to be °C
b. Set the 0 and 100 scale to be the same as the
SECONDARY_VALUE_RANGE
6. Put the AI Block back into Auto mode.
7. Follow Host Procedure Download Schedule into Block.
Filtering
The filtering feature changes the response time of the device to smooth
variations in output readings caused by rapid changes in input. Adjust the
filter time constant (in seconds) using the PV_FTIME parameter. Set the filter
time constant to zero to disable the filter feature.
Process Alarms
Process Alarm detection is based on the OUT value. Configure the alarm
limits of the following standard alarms:
• High (HI_LIM)
• High high (HI_HI_LIM)
• Low (LO_LIM)
• Low low (LO_LO_LIM)
In order to avoid alarm chattering when the variable is oscillating around the
alarm limit, an alarm hysteresis in percent of the PV span can be set using the
ALARM_HYS parameter. The priority of each alarm is set in the following
parameters:
•HI_PRI
•HI_HI_PRI
•LO_PRI
•LO_LO_PRI