BEKA BA627E-SS, Manual, Page: 3 / 18

1. DESCRIPTION
The BA627E-SS is a rugged general purpose, loop
powered panel mounting Set Point Station which en-
ables the current flowing in a 4/20mA loop to be
manually adjusted via the front panel push buttons,
or an optional external rotary control. The main ap-
plication is the adjustment of a plant parameter, such
as a controller set point or an actuator position, from
within a process area.
Housed in a rugged stainless steel enclosure with an
IP66 impact resistant front panel, the
BA627E-
SS is ideal for applications in harsh and marine en-
vironment.
To simplify adjustment the Set Point Station incor-
porates a 5 digit display and a 31 segment bargraph
which may be calibrated to show the 4/20mA loop
current in any linear engineering units. An optional
factory fitted backlight, which may be loop or separ-
ately powered, enables this display to be read in all
lighting conditions.
The BA627E-SS loop current is adjustable between
3 and 22mA but the range may be restricted if only
limited adjustment is required. In addition to the out-
put being continuously variable, five pre-set output
currents may be configured and subsequently selec-
ted from the front panel push buttons. To minimise
plant disturbance the maximum output rate of
change may be defined.
2. OPERATION
Fig 1 shows a simplified block diagram of the
BA627E-SS manual Set Point Station. The 4/20mA
current flowing in the loop may be manually set at
any value between approximately 3 and 22mA using
the front panel
&
and
*
push buttons. Initially the
output current changes slowly, but after the button
has been pressed for five seconds the rate of
change accelerates to allow large changes to be
made quickly. The five pre-set outputs, which are
selectable via the instruments front panel push but-
tons, allow the operator to quickly select frequently
used plant set points.
To prevent plant disturbance the maximum rate of
output current change initiated by operating the front
panel push buttons, switching between pre-set out-
puts or using an optional external encoder may be
defined.
The output resistance of the BA627E-SS is very
high, within the specified operating voltage range,
the loop current will therefore be unaffected by
changes in the supply voltage.
CAUTION
The BA627E-SS output should not be used for
critical safety applications.
Versatile calibration facilities allow the 5 digit internal
display to show the 4/20mA loop current in linear en-
gineering units.
For example, in an application
where the BA627E-SS is being used to adjust the set
point of a speed controller, the internal indicator may
be calibrated to display the required speed in
RPM.
For applications in poorly illuminated areas a factory
fitted green backlight is available which may be loop
or separately powered.
When loop powered the
backlight produces background illumination enabling
the display to be read at night or in poor lighting con-
ditions.
No additional power supply or field wiring
are required, but the Set Point Station voltage drop is
increased. When separately powered, the backlight
is brighter but additional field wiring is required.
Fig 1 Simplified block diagram of BA627E-SS
3