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156 UDC 3300 Controller Product Manual 4/00
5.6 Operating Modes
Available modes
The controller can operate in any of three basic modes:
• Manual—One or Two Loops
• Automatic with Local Setpoint—One or Two Loops
• Automatic with Remote Setpoint—One or Two Loops
• Manual Cascade
• Automatic Cascade
The manual and automatic control modes with Local and Remote setpoint
are standard with the instrument; cascade control is optional.
Mode definitions
Table 5-7 lists the available modes and their definitions.
Table 5-7 Operating Mode Definitions
Operating Mode Definition
MANUAL In the manual mode, the operator directly controls the
controller output level. The process variable and the
percent output are displayed. The configured High and Low
Output Limits are disregarded and the operator can change
the output value using the increment and decrement keys to
the limits allowed by the output type (0 % to 100 % for a
time proportioning output or –5 % to 105 % for a current
output).
AUTOMATIC with LOCAL
SETPOINT
In automatic local mode, the controller operates from the
local setpoints and automatically adjusts the output to
maintain the setpoint at the desired value.
In this mode you can adjust the setpoint.
See Section 5.7 - Setpoints.
AUTOMATIC with
REMOTE SETPOINT
In automatic remote mode, the controller operates from the
setpoint measured at the Remote setpoint input.
Adjustments are available to ratio this input and add a
constant bias before it is applied to the control equation.
See Section 3 - Configuration, Control Set up group.
MANUAL CASCADE In the manual cascade mode, both control loops are in
manual although there is still only one output active. This
mode is used to bring both loops into a reasonable
operation area, at which point the unit is placed into the
automatic cascade mode.
If Loop 1 is placed in Manual control mode, then Loop 2, if
in auto, is then placed in a pseudo-manual mode thereby
eliminating output bumps when Loop 1 is returned to
Automatic control mode.
AUTOMATIC CASCADE In Automatic cascade mode, there are two control loops,
with one loop’s output acting as the setpoint for the second
control loop. There is only one physical output in this mode.