4
2. OPERATION
Fig 1 shows a simplified block diagram of the
BA688CF Fieldbus Display. When the optional
alarms and external switches are not used, the
instrument only requires a two-wire connection to
the fieldbus.
How much of the BA688CF configuration can be
performed via the fieldbus depends upon the
instrument version and the system host.
Parameters that can not be configured via the
fieldbus can be set via the six front panel push
buttons. Menus enable the required standard
display format to be selected and the units of
measurement, plus tag information for each
displayed fieldbus variable to be entered. Each
fieldbus variable may be individually offset and
scaled, and when a standard screen including a
bargraph is selected, the limits of each bargraph
can be set. Alarm function and setpoints can
also be configured.
Fieldbus configuration files for the BA688CF may
be downloaded from the appropriate Fieldbus
Foundation or Profibus web sites, or from the
BEKA associates web site at ww.beka.co.uk.
Fig 1 Simplified block diagram of BA688CF
2.1 Controls
The user can scroll through the display screens
by operating the
Up
or
Down
push-buttons. The
number of screens available depends upon how
the BA688CF display has been configured. If
one fieldbus variable per screen has been
configured, eight screens will be present; if four
fieldbus variables per screen have been
configured, only two screens will be available.
Irrespective of the number of fieldbus variables
assigned to the BA688CF, the instrument always
has provision for displaying eight variables.
Unassigned inputs are displayed as zero with a
bad data warning i.e. light digits on a dark
background. When a custom display format,
which requires programming is used, the number
of fieldbus variables displayed may be defined.
If enabled, operating the
P
and
Up
push buttons
simultaneously activates the Quick Access Menu,
allowing the user to adjust the display contrast
without providing access to any of the other
configuration parameters. Additional security
may be provided by an optional access code.
