Emerson 644 manual Filtering, Process Alarms

Rosemount 644

Reference Manual

00809-0400-4728, Rev AA June 2011

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

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