Flowserve StarPac II Control Valves - Manual (Page 17)

Remote Refresh Rate - This option sets up a time-out on the
receipt of fresh setpoint data when set to operate with a remote
setpoint. If the setpoint is not refreshed within the time frame
entered in this field, the unit will go into a loss-of-command trip
as set up in the C
ONFIGURE menu. A value of “0” disables this
feature and makes the electronics think that the Mode source is
digital. Note that if the digital source is selected, the unit will
hold at the last setpoint indefinitely.
Command - Provides three options used to change the valve
position command and configure the source of the valve command.
Command % - Allows the direct input of the valve position
command as a percentage of valve travel. Zero percent is
closed and 100 percent is open--provided the unit is in Manual
mode with the digital command selected.
Analog/Digital - This option selects where the StarPac II system
will receive the valve position command information.
“Digital” indicates that the keypad or the StarTalk software can
be used to change the valve position command.
“Analog” prompts the StarPac II to use the 4-20 mA signal from
analog input No. 1 as the valve position command.
“Remote” is used when a host system such as a PLC or DCS is
used to write the valve position command to the unit digitally.
Remote Refresh Rate - This option sets up a “timeout” on the
receipt of fresh, valve-position command data when set to
operate with a remote command. If the valve position command
is not refreshed within the time frame entered in this field, the
unit will go into a loss of command trip (as set up in the
C
ONFIGURE menu). A value of “0” disables this feature. Note
that if the digital source is selected, the unit will hold at the last
valve position command indefinitely.
Proportional Band - Sets the proportional band for the controller.
Proportional Band = 100/gain or gain =100/prop. band. Since
proportional band is the inverse of gain, the larger the band value,
the smaller the controller gain.
Reset Rate - This is the integrator term in the PID controller,
referring to the action at which the rate of change of output is
proportional to the error input. “Reset” is the parameter that controls
how the integral control action affects the final control element. The
larger the value, the faster the system tries to eliminate the offset
error. Units are repeats/min.
Derivative Time - Sets the time on the derivative control action of
the PID controller. This time is the interval at which the rate action
advances the effect of the gain on the final control element. Units
are in seconds.
PID Action - This variable determines the response of the controller
to error. Reverse action will cause an air-to-open valve to begin to
close when the process variable is greater than the setpoint. Direct
action has the opposite effect. The following table gives some
guidelines for control action settings:
StarPac II User Interface Manual 11