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Instruction Manual
IM-106-880C, OI
September 2009
7-51
Hazardous Area OCX 8800
ARITHMETIC (ARTHM)
FUNCTION BLOCK
Figure 7-22. 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.
Mode sheds
from RCAS to
AUTO
1. Remote Cascade Value
2. Shed Timer
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 re-
source block is set too low. Increase the value.
Mode sheds
from ROUT to
MAN
1. Remote output value
2. Shed timer
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 re-
source block is set too low. Increase the value.
Process and/or
block alarms
will not work
1. Features
2. Notification
3. Status Options
1. FEATURES_SEL does not have Alerts en-
abled. 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.
Symptom Possible Causes Corrective Action
OUTIN
IN_LO
IN_1
IN_2
IN_3
ARTHM
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