Emerson Rosemount OCX 8800, Инструкция по эксплуатации

Страница: 187 / 306

Instruction Manual
IM-106-880C, OI
Section 7: Foundation
Fieldbus
April 2017
Mode
s
16
1
7.15.2 Modes
The ISEL function block supports three modes of operation as defined by the MODE_BLK
parameter:
• Manual (Man) The block output (OUT) may be set manually.
• Automatic (Auto) OUT reflects the selected value.
• Out of Service (O/S) The block is not processed. The BLOCK_ERR parameter shows Out
of Service. In this mode, changes caNn be made to all configurable parameters. The
target mode of a block may be restricted to one or more of the supported modes.
7.15.3 Alarm Detection
A block alarm will be generated whenever the BLOCK_ERR has an error bit set. The types of block
error for the ISEL block are defined above.
Alarms are grouped into five levels of priority, Table 7-37 .
Table 7-37 Alarm Priorities
0 The priority of an alarm condition changes to 0 after the condition that caused the alarm is corrected.
1 An alarm condition with a priority of 1 is recognized by the system, but is not reported to the operator.
2 An alarm condition with a priority of 2 is reported to the operator, but does not require operator attention
(such as diagnostics and system alerts).
3 to 7 Alarm conditions of priority 3 to 7 are advisory alarms of increasing priority.
8 to 15 Alarm conditions of priority 8 to 15 are critical alarms of increasing priority.
7.15.4 Block Execution
The ISEL function block reads the values and statuses of as many as four inputs. To specify which
of the six available methods (algorithms) is used to select the output, configure the selector
type parameter (SEL_TYPE) as follows:
• max selects the maximum value of the inputs.
• min selects the minimum value of the inputs.
• avg calculates the average value of the inputs.
• mid calculates the middle of three inputs or the average of the middle two inputs if four
inputs are defined.
• 1st Good selects the first available good input.
• Hot Backup latches on the selected input and continues to use it until it is bad.
If DISABLE_N is active, the associated input is not used in the selection algorithm.
If OP_SELECT is set to a value between 1 and 4, the selection type logic is overridden and the
output value and status is set to the value and status of the input selected by OP_SELECT.
SELECTED will have the number of the selected input unless the SEL_TYPE is average, in which
case it will have the number of inputs used to calculate its value.
Priority Priority Description Number