Fisher DPR900 User Manual page 47

Controls and Indicators
3-11
The controller can also be configured to switch to a preconfigured
ESP value upon certain discrete switching and fault situations, Use
FCODE 12 to configure this value.
Function Parameters FCODE Range Unit Increment Default Selected
Valtle V&k?
Extra Setpoint 12
MI?E.
a"Y
1 digit 0
Internal SP value
3.8
Computer Control
Computer control is available when the red C in the upper left of the
digital display is lit. Use the R button to select computer control when
it is available. When computer control is active the R button green
DPAm2417
LED is on. When the controller is in local control mode, the computer
can read values from the controller. Under computer control, two
discrete input signals control the setpoint value, the output signal or
accept control signal changes via the KG-485 communications link.
The following conditions apply to computer control:
n
If the controller has been switched to computer control (R button
lit), switching between computer mode and local mode is
accomplished via an external discrete signal.
n
If the external discrete switching signal is deactivated, the
controller switches to local mode and the green LED in the R
button remains lit.
n
The controller then uses the LSP, RSP, or ESP, depending on
which options are used for FCODE 141 and 142.
3.9 Autotuner Operation
The autotuner is a utility for automatic setting of PID parameters. This
function can also be used with non-linear processes when used with
gain. Before tuning is started, ensure that the process is stable at a
position close to the required working point, i.e. SP = PV.
With the controller in either Remote, Auto or Manual, use the TUNE
button to start the autotuner. The green LED in the button blinks while
the autotune mode is active. For slow processes the autotune function
may take as long as 32 hours, the maximum time the autotuner will
run. The controller returns automatically to auto mode when the
tuning procedure is complete.
May 1991 LJM6.1:DPR900:9102