ABLE BEKA BA504E, Инструкция по установке и обслуживанию

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4
2.1 Controls
The indicators are controlled and calibrated via
four push-button switches located behind the
instrument control cover, or as an option on the
control cover. 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 + ▼ Indicator displays firmware number
followed by version.
P + ▲ Provides 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 Provides access to the configuration
menu via optional security code.
Note: * BA524E 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
Both 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 typical applications 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 BA524E 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
Both indicators may be driven from any 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 BA524E
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.