Yokogawa Wireless Temperature Transmitter YTA510 - Manual (Page 84)

<Appendix 4. PID Block>
A4-8
IM 01C50T02-01E
A4.14 Initialization and Manual
Fallback (IMan)
Initialization and manual fallback denotes a set of
actions in which a PID block changes mode to IMan
(initialization and manual) and suspends the control
action. Initialization and manual fallback takes
place automatically as a means of abnormality
handling when the following condition is met:
• The quality component of BKCAL_IN.status is
Bad.
- OR -
• The quality component of BKCAL_IN.status is
Good (c)
- AND -
The sub-status component of BKCAL_IN.status
is FSA, LO, NI, or IR.
The user cannot manually change the mode to
IMan. A mode transition to IMan occurs only when
the condition above is met.
A4.15 Manual Fallback
Manual fallback denotes an action in which a
PID block changes mode to Man and suspends
the control action. Manual fallback takes place
automatically as a means of abnormality handling
when the following condition is met:
• IN.status is Bad except when the control action
bypass is on.
To enable the manual fallback action to take place
when the above condition is met, Target to Manual if
BAD IN must be specified beforehand in STATUS_
OPTS.
The table below shows the options in STATUS_
OPTS.
Options in
STATUS_
OPTS
Description
IFS if BAD IN Sets the sub-status component of
OUT.status to IFS if IN.status is Bad
except when PID control bypass is on.
IFS if BAD
CAS IN
Sets the sub-status component of
OUT.status to IFS if CAS_IN.status
is Bad.
Use
Uncertain as
Good
Does not regard IN as being in Bad
status when IN.status is Uncertain (to
prevent mode transitions from being
affected when it is Uncertain).
Target to
Manual if
BAD IN
Automatically changes the value of
MODE_BLK.target to MAN when IN
falls into Bad status.
Target to next
permitted
mode if BAD
CAS IN
Automatically changes the value of
MODE_BLK.target to Auto (or to Man
if Auto is not set in Permitted) when
CAS_IN falls into Bad status.
A4.16 Auto Fallback
Auto fallback denotes an action in which a PID
block changes mode from Cas to Auto and
continues automatic PID control with the user-set
setpoint. Auto fallback takes place automatically
when the following condition is met:
• IN.status (data status of IN) is Bad except when
the control action bypass is on.
To enable the manual fallback action to take place
when the above condition is met:
• Target to next permitted mode if BAD CAS
IN must be previously specified in STATUS_
OPTS.
- AND -
• Auto must be previously set in MODE_BLK.
permitted.