Figure 7-25 Arithmetic (Arthm) Function Block - Emerson Rosemount OCX8800 Instruction Manual

Instruction Manual
IM-106-880C, OI
Symptom Possible Causes
Mode sheds from RCAS 1. Remote Cascade Value
to AUTO
2. Shed Timer
Mode sheds from 1. Remote output value
ROUT to MAN
2. Shed timer
Process and/or block 1. Features
alarms
will not work
2. Notification
3. Status Options
7.13 Arithmetic (ARTHM) Function Block

Figure 7-25 Arithmetic (ARTHM) Function Block

The Arithmetic function block provides the ability to configure a range extension function for a
primary input and applies the nine (9) different arithmetic types as compensation to or
augmentation of the range extended input. All operations are selected by parameter and input
connection.
The nine (9) arithmetic functions are Flow Compensation Linear, Flow Compensation Square
Root, Flow Compensation Approximate, BTU Flow, Traditional Multiply and Divide, Average,
Summer, Fourth Order Polynomial, and Simple HTG Compensate Level.
This Arithmetic function block supports mode control (Auto, Manual, Out of Service). There is
no standard alarm detection in this block.
Arithmetic (ARTHM) Function
Block
Corrective Action
1. Host system is not writing RCAS_IN with a quality and status of
"good cascade" within shed time (see 2 below).
2. The mode shed timer, SHED_RCAS in the resource block is set too
low. Increase the value.
1. Host system is not writing ROUT_IN with a quality and status of
"good cascade" within shed time (see 2 below).
2. The mode shed timer, SHED_RCAS, in the resource block is set
too low. Increase the value.
1. FEATURES_SEL does not have Alerts enabled. Enable the Alerts
bit.
2. LIM_NOTIFY is not high enough. Set equal to MAX_NOTIFY.
3. STATUS_OPTS has Propagate Fault Forward bit set. This should be
cleared to cause an alarm to occur.
IN
IN_LO
ARTHM
IN_1
IN_2
IN_3
Section 7: Foundation
OUT
Fieldbus
April 2017
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