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DISCRETE INPUT SET
Figure 4-32. Discrete Input Proximity Detection Function
Valve Position Proximity Detection
Channels 30 through 33 provide valve position
proximity detection for the DI block. The transducer
block Travel Alert Point and Travel Alert Deadband
parameters are also used with the valve position
proximity, but they provide a different function. The
Travel Alert Point for the selected channel determines
the center point for the position to be detected. The
Travel Alert Deadband for the selected channel sets
the upper and lower trigger points, or the width of the
proximity detection band. A 1% deadzone exists
above and below this band that the travel must exceed
to clear the detected position. Figure 4-32 illustrates
the operation of the proximity detection function.
Travel Alert Point refers to Travel Lo Alert Point,
Travel Hi Alert Point, Travel Lo Lo Alert Point, and
Travel Hi Hi Alert Point in table 4-78. Travel Alert
Deadband refers to Travel Lo Alert Deadband, Travel
Hi Alert Deadband, Travel Lo Lo Alert Deadband, and
Travel Hi Hi Alert Deadband in table 4-78.
0= Not Active, 1= Active
Table 4-78 lists the transducer block parameters used
for proximity detection with DI block channels 30
through 33.
Field Value Processing
The Invert bit of the IO_OPTS [13] parameter may be
used to logically invert the value of FIELD_VAL_D [17]
before it is stored as PV_D [7]. PV_FTIME [16] may
December 2009
Table 4-77. Transducer Block Parameters Used with Discrete
Input Function Block Channels 26 through 29 (Variable Limit
DISCRETE INPUT
CLEARED
DEADZONE, 1%
Travel Lo Lo Alert Point
OF TRAVEL
Travel Lo Lo Alert Deadband
TRIGGER POINT FOR
Travel Lo Alert Point
DOWNWARD VALVE
Travel Lo Alert Deadband
TRAVEL DETERMINED
BY TRAVEL ALERT
Travel Hi Alert Point
DEADBAND
Travel Hi Alert Deadband
Travel Hi Hi Alert Point
CENTER POINT OF
Travel Hi Hi Alert Deadband
PROXIMITY DETECTION
DETERMINED BY
TRAVEL ALERT POINT
Table 4-78. Transducer Block Parameters Used with Discrete
TRIGGER POINT FOR
UPWARD VALVE TRAVEL
Transducer Block
DETERMINED BY TRAVEL
ALERT DEADBAND
Travel Lo Lo Alert Point
Travel Lo Lo Alert Deadband
Travel Lo Alert Point
Travel Lo Alert Deadband
Travel Hi Alert Point
Travel Hi Alert Deadband
Travel Hi Hi Alert Point
Travel Hi Hi Alert Deadband
be used to set the length of time that FIELD_VAL_D
[17] must be in a new state before that new state is
reflected in PV_D. The PV_D [7] value goes to the
mode switch where it becomes OUT_D [8] when the
actual mode is AUTO. OUT_D [8] is also tested for an
alarm state.
Alarm Detection
To select the state that initiates an input alarm, and to
set discrete alarm substatus in the output, configure
the DISC_LIM [23] parameter. You can enter any
value between 0 and 255. A value of 255 disables the
alarm. When OUT_D [8] matches the DISC_LIM [23]
state, the discrete value of an alarm is set.
DI Function Block
Switch)
Transducer Block
Parameter
Lo Lo Limit Switch Trip Point
Lo Lo Limit Switch Deadband
Lo Limit Switch Trip Point
Lo Limit Switch Deadband
Hi Limit Switch Trip Point
Hi Limit Switch Deadband
Hi Hi Limit Switch Trip Point
Hi Hi Limit Switch Deadband
Input Function Block Channels 30 through 33
Parameter
Lo Lo Proximity Detection Center Point
Lo Lo Proximity Detection Width
Lo Proximity Detection Center Point
Lo Proximity Detection Width
Hi Proximity Detection Center Point
Hi Proximity Detection Width
Hi Hi Proximity Detection Center Point
Hi Hi Proximity Detection Width
Note
Invert is the only I/O option that the DI
block supports. You can set the I/O
option only when the block mode is
Out of Service.
Parameter Function
4
Parameter Function
4-163
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