4
2.1 Controls
The indicators are controlled and calibrated via
four front panel push-buttons located below the
display. In the display mode i.e. when the
indicator is displaying a process variable, these
push-buttons have the following functions:
P
While this button is pushed the
indicator will display the input current in
mA, or as a percentage of the
instrument span depending upon how
the indicator has been conditioned.
When the button is released the normal
display in engineering units will return.
The function of this push-button is
modified when optional alarms are
fitted to the indicator.
▼
While this button is pushed the
indicator will display the numerical
value and analogue bargraph* the
indicator has been calibrated to display
with a 4mA
Φ
input. When released the
normal display in engineering units will
return.
▲
While this button is pushed the
indicator will display the numerical
value and analogue bargraph* the
indicator has been calibrated to display
with a 20mA
Φ
input. When released
the normal display in engineering units
will return.
E
No function in the display mode unless
the tare function is being used.
P +
▼
Firmware number followed by version.
P +
▲
Direct access to the alarm setpoints
when optional alarms are fitted to the
indicator and the ‘ACSP’ access
setpoints in display mode function has
been enabled.
P + E
Access to configuration menu via
optional security code.
Note:
*
BA527E and BA528E only
Φ
If the indicator has been calibrated
using the CAL function, calibration
points may not be 4 and 20mA.
3. APPLICATIONS
3.1 Transmitter loops
All the models may be connected in series with
any 4/20mA current loop and calibrated to display
the measured variable or control signal in
engineering units.
Figs 2 illustrate a typical application in which an
indicator is connected in series with a 2-wire
transmitter.
Fig 2 Indicator in a transmitter loop
Considering the example shown in Fig 2, the sum
of the maximum voltage drops of all the
components in the loop must be less than the
minimum power supply voltage.
Minimum operating voltage of 2-wire Tx
10.0
Maximum voltage drop caused by controller
5.0
Maximum voltage drop caused by BA507E
1.3
Maximum voltage caused by cables
0.4
_____
16.7V
Therefore at 20mA in this example the power
supply must have a minimum output of 16.7V
3.2 Remote indication
All the indicators may be driven from a 4/20mA
signal to provide a remote indication. Fig 3 shows
a typical application in which the 4/20mA output
from a gas analyser is connected to a BA507E
loop powered indicator to provide a remote
indication of the analyser’s output. Again it is
necessary to ensure that the voltage capability of
the 4/20mA source is greater than the sum of the
voltage drops introduced by the indicator and the
cable resistance.
