Yokogawa EJX930A - Manual (Page 51)

<6. Explanation of Basic Items>
6-10
IM 01C25T02-01E
6.5 AI Function Block
The AI function block is a unit of the software and
executed according to the system schedule. During
execution, it incorporates data from the SENSOR
transducer block. After execution, it updates analog
outputs and processes newly generated alarms. AI
function blocks can provide a discrete output which
shows the status of LO, LO_LO, HI, or HI_HI. In
terms of function, there is no difference between the
three AI function blocks provided in EJX.
6.5.1 Function Blocks
The AI function block, via the Channel, incorporates
analog signals from the transducer block, performs
scaling processing, filtering, low-cut, and alarm
processing before outputting. It has the function to
generate a discrete output. Figure 6.4 presents the
AI function block.
6.5.2 Block Mode
The Block modes permitted for the AI function
block are Automatic (Auto), Manual (Man), and
Out of Service (O/S). When the Block mode of RB
(Resource Block) is Out of Service (O/S), Actual
is Out of Service (O/S) even if Automatic (Auto) or
Manual (Man) is written to Target.
6.5.3 IO_OPTS
IO_OPTS is a parameter used to select whether
options regarding input and output signals should
be enabled or disabled. In the case of the AI
function block, the only available option is “Low
cutoff”. When enabling the low cut function for
outputs, set this option.
6.5.4 STATUS_OPT
STATUS_OPT is a parameter to select options
regarding the status of signals. The AI function
block offers four options: Propagate Fault Forward,
Uncertain if Limited, BAD if Limited, and Uncertain if
Man mode.
Propagate Fault Forward
If the status from the sensor is Bad, Device failure
or Bad, Sensor failure, propagate it to OUT without
generating an alarm. The use of these sub-statuses
in OUT is determined by this option. Through this
option, the user may determine whether alarming
(sending of an alert) will be done by the block or
propagated downstream for alarming
Uncertain if Man mode
When the “Uncertain if Man” is enabled and the
Actual mode is Man, the OUT signal status should
be “Uncertain”.
Scaling
OUT_SCALE
Filter
PV_FTIME
Cutoff
LOW_CUT
L_TYPE
Simulate
SIMULATE.
Transducer Value
SIMULATE.Enable
Simulate
SIMULATE.
Simulate Value
Scaling
XD_SCALE
FIELD_VAL.Value
IO_OPTS.Low cutoff
OUT_D_SEL
PV.Value
MODE_BLK.Actual
Alarms
LO, LO_LO
HI, HI_HI
/100
/100
Disable Enable
Direct
Indirect
=0(Disable)
Auto =1(Enable)
OUT
OUT_D
Ind.Sqr Root
F0608.ai
Figure 6.4 Diagram of the AI Functional Block