|
Data
and power
are normally supplied by a 2 wire serial data link from a certified galvanic
communications isolator in the safe area. This isolator, which can power and
communicate with one or two serial text displays, can be configured with an
RS232 or RS422 safe area port. Alternatively, a 3 wire system requiring an
additional isolator may be used to communicate with up to four text displays.
The
high contrast liquid crystal display incorporates a green
backlight that is powered by the serial data link enabling the display to be
read in all lighting conditions from full sunlight to total darkness.
Six
push-buttons (four in the case of the BA484D) which may be used for
operator acknowledgments or controls are included below the display. If larger
industrial switches are required, up to six external push-buttons may be
connected to either version of the text display. When the remote switches are
activated, the front panel push-buttons are automatically disabled.
Two isolated
switch outputs,
which are controlled via the serial data link, comply with the requirements for
simple apparatus and may be used to switch almost any certified intrinsically
safe device such as a sounder, beacon or a valve.
Nine
selectable standard screen formats display one, two,
three or four variables, with units of measurement, tag descriptions and
bargraphs on some screens. The use of a standard display screen format greatly
simplifies system design.
Modbus
protocol
enables up to eight process variables together with their units of measurement
and tag descriptions to be displayed. When used with one of the nine standard
screen formats, no programming is required apart from setting the text display's
communication parameters and writing each Modbus variable into the text
display's Modbus register address map. If a custom screen layout is required in
a Modbus system this can be constructed using the BEKA protocol.
BEKA
protocol
allows custom screens using five different font sizes together, lines, boxes and
bargraphs to be produced and stored in non-volatile memory. Simple bit map
graphics may be downloaded and stored. Information can also be written to a
hidden screen that may be displayed when required.
Legacy
protocol
enables the BA484D to replace an MTL643 ( or the BA488C to replace
an MTL644) to provide ATEX certification and a display backlight. No software or
galvanic isolator changes are required and the BA488C will fit the
existing panel cut-out. If required, simple modifications to the host software
will allow the enhanced features of the BA484D to be used i.e. five font
sizes, simple graphics, additional operator buttons and a second solid state
output.
ATEX
intrinsic safety certification of the BA488C allows
installation in all gas hazardous areas (and the BA484D is certified for
both dust and gas hazardous areas). Both solid state outputs comply with the
requirements for simple apparatus and may be used to switch almost any certified
intrinsically safe device such as a sounder, beacon or a valve.
Scripts
are a
sequence of commands, downloaded to and stored in non-volatile memory by the
Text Display, that can be executed by the instrument without intervention from
the host. For example a routine may be written to monitor the instruments
pushbuttons and to change the displayed screen or variable depending upon which
button has been operated.
Pattern matching
is a
powerful feature that allows the Text Display to capture and display data
contained in a proprietary ASCII serial string, such as that from a weighing
system or barcode reader primarily intended for printing.
The
enclosure of
the BA484D is moulded in glass reinforced polyester (GRP), has stainless
steel fittings, silicone gaskets and an armoured glass window. Its robust
construction provides IP66 protection. A separate terminal compartment allows
the BA484D to be installed and terminated without exposing the display
electronics.
The front panel of
the BA488C has IP66 protection and a neoprene gasket seals the joint
between the text display and the panel, making it suitable for use in areas that
will be hosed.
|
