Micromod MOD: Modcell 2050R Users Guide - Manual (Page 142)

IB-23C650
BASIC OPERATION
AUTO/MANUAL TRANSFER
Transfer from auto to manual is accomplished by pressing the manual key.
Either of the digital inputs may be used to select manual if configured to do
so. When the controller is in manual mode the upper status display will show
[MAN].
Transfer from manual to automatic is made by pressing the auto key. Either
of the two digital inputs may be used to select auto if configured to do so.
When in automatic, the upper status display will show [AUT].
Auto/Manual Transfer with Local Set-Point
When the controller is operating on local set-point, transfers from automatic to
manual and from manual to automatic are always bumpless. After switching
from local manual to local automatic, the process variable will be under
automatic control in response to the adjustment of local set-point in the
controller.
Auto/Manual Transfer with Local Set-Point Tracking
If the controller has been configured for local set-point tracking, the local set-
point tracks the process value when the controller is in manual, and the
process is always at the local set-point when a transfer to automatic is made,
regardless of set-point limits. If a set-point was enabled as “fixed” in the
SETPTS MENU, set-point tracking will not apply to that set-point.
Auto/Manual Transfer without Local Set-Point Tracking
If the controller does not have local set-point tracking, the local set-point and
process may not be at the same value at the time of transfer from manual to
automatic. The transfer will be bumpless, but the response following the
transfer depends on the controller setup. If the controller has integral
response, the process will ramp toward the local set-point at the reset rate. If
the controller does not have integral response, the local set-point/process
deviation at the time of transfer will be maintained. This deviation can be
eliminated by using a fixed manual reset value or a calculated manual reset
value, by returning to manual, adjusting output to eliminate the deviation, then
switching bumplessly back to automatic with local set-point.
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