BEKA Advisor A90-SS, Руководство пользователя

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7.3.15 Displaying setpoints on the bargraph
One of the selectable bargraph formats
Alr5P
allows a low or a high setpoint plus the displayed
value to be represented, or a low and a high
setpoint plus the displayed value to be represented
by the bargraph as shown in Fig 14.
Fig 14 Displayed value and setpoints on bargraph
The bargraph area below the low alarm setpoint
and the area above the high alarm setpoint are
activated. The displayed variable is represented
by an activated segment which moves between
these low and high alarm setpoints.
When the activated segment representing the
displayed variable is adjacent to the area
representing the low or high alarm setpoints, the
segment flashes. When a displayed variable
equals the low or high alarm the complete
bargraph representing the activated alarm flashes
irrespective of whether the alarm output has been
delayed or cleared.
For this function to operate
5P1
must be
conditioned as a low alarm and
5P2
as a high
alarm;
5P1
must always be less than
5P2
.
Incorrect configuration is shown by a flashing
bargraph scale with no activated bars.
7.4 4/20mA output and transmitter supply
The A90-SS panel meter can be supplied with a
factory fitted isolated 4/20mA current sink and a
galvanically isolated 24V dc supply as shown in
Fig 1. Connecting the 24V supply in series with
the current sink produces a 4/20mA current source
output. The 24V dc output may also be used to
power a remote transmitter.
7.4.1 4/20mA output loop design
The 4/20mA output is a current sink i.e. not
powered, but it is totally isolated from all other A90-
SS meter circuits. It is effectively a 2-wire 4/20mA
transmitter requiring a minimum supply of 5V with
its current controlled by any required part of the
A90-SS meter display. Terminals 18 and 19 may
be connected to any other instrument which will
accept a 4/20mA transmitter input as shown in
Fig 15.
Fig 15 Current sink output
Connecting the 4/20mA current sink in series with
the 24V dc power supply produces a 4/20mA
current source output capable of driving up to a
19V load such as a loop powered remote indicator.
Terminals 19 and 21 are isolated and may be
connected to any other instrument which will
accept a 4/20mA input as shown in Fig 16.
Fig 16 Current source output
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