Emerson Process Management ControlWave XFC - Manual (Page 33)

CI-ControlWave XFC Introduction / 1-19
convienience, a +V and ground terminal are provided on either side of the RS-485 Port (for
use in powering model 3808 Transmitters). Note: Only half-duplex RS-485 networks are
supported.
Comm. Port Defaults
From the factory COM1 defaults to 115.2 kbd using the BSAP Protocol. The remaining
serial communication ports, i.e., COM2 and COM3 default as follows: (COM2 – BSAP Slave
@ 9600 Baud) (COM3 – BSAP Master @ 9600 Baud [for use with Bristol Babcock 3808 MVT
Transmitters])
1.5.5.1 BSAP Message Support
The ControlWave XFC supports the same subset of BSAP messages as the other
ControlWave products.
1.5.6 Discrete and Analog I/O XFC Functionality
ControlWave XFC explosion proof gas flow meters are equipped with a variety of Inputs
and Outputs (see Section 1.3.3.2). While using the standard application program, inputs
and outputs required for measurement and control are mapped to the application using the
configuration Web pages. Analog Alarm limits for variables required by the standard
application program are defined via the configuration Web pages. Discrete Input alarms
associated with the standard application program can be enabled or disabled on a per point
basis via the configuration Web pages. Control algorithms (flow control, sampler control,
odorant control, etc.) are selected via the configuration Web pages.
1.5.6.1 Flow Rate Control - DDC (jog control) using PID
When the user configures the ControlWave XFC to perform flow rate control, the two
digital output signals are wired to the Open and Close inputs of a controller. The
ControlWave XFC uses a Proportional/Integral/Derivative (PID) algorithm to cause the
measured rate of flow to match a user-entered setpoint. When the flow rate is below the
setpoint, the Open output is pulsed. When the flow rate is above the setpoint, the Close
output is pulsed. The PID equation calculates the duration of the Open or Close pulse. The
minimum pulse duration is 1.0 seconds. The user changeable parameters are:
• Flow Setpoint in MSCFH
• Deadband in % of setpoint
• Proportional Gain
• Integral Time in repeats/minute
• Derivative Time in seconds
• Valve Travel Time (full close to full open)
• Process Control Limiting
• Pressure Override Limits
The flow control algorithm runs once per second.
1.5.6.2 Pulse Output for External Totalizer or Sampler
When the ControlWave XFC is configured to provide a pulse output based on volume, the
operator provides a control volume and a pulse duration. After each calculation cycle, an
internal volume accumulator is compared to the control volume. If the accumulator exceeds
the control volume then a pulse is output and the accumulator is reduced by the volume