9.6 4/20mA output
Both the BA537E and BA538E Rate Totalisers can be
supplied with a factory fitted galvanically isolated
4/20mA output which may be configured to represent
the rate or total display. Only one output option can
be fitted to a BA537E.
9.6.1 System design
The Rate Totalisers 4/20mA output is a galvanically
isolated passive current sink i.e. not powered, but it is
totally isolated from all other Rate Totaliser circuits. It
is effectively a 2-wire 4/20mA transmitter requiring a
minimum supply of 5V with its current being controlled
by the Rate Totaliser. The 4/20mA output terminals
C1 and C3 may be connected to any other instrument
which will accept a 4/20mA transmitter input and has
a least a 10V output.
Fig 16 Application of 4/20mA output
9.6.2 Configuration
When a Rate Totaliser is supplied with an optional
4/20mA output the configuration menu is extended as
shown in Fig 17.
The 4/20mA output sub-menu is
accessed via the
4-20 oP
function.
The 4/20mA output sub-menu allows the 4/20mA
output to be controlled by the rate or the total display
and to be scaled.
Fig 17 4/20mA output configuration sub-menu
9.6.3 4/20mA output:
4-20 oP
Access the Rate Totaliser's configuration menu as
described in section 5.2. Using the
&
or
*
push
buttons scroll though the menu until
4-20 oP
is
displayed, pressing
(
will then access the 4/20mA
output sub-menu which is shown in Fig 17.
9.6.4 Enable 4/20mA output:
Enbl
This function allows the 4/20mA current output to be
disabled or enabled without altering the calibration.
Using the
&
or
*
push button select
EnbL
in the
4-20 op
sub-menu and press
(
to reveal the
existing setting
on
or
oFF
.
The function can be
changed by pressing the
&
or
*
push button
followed by the
)
button to return to
EnbL
prompt in
the sub-menu.
9.6.5 Select rate or total source:
4-20tYPE
The 4/20mA output current can represent the Rate
Totaliser's rate or total display, this should be
defined before any other current output functions are
adjusted.
Using the
&
or
*
push button select
4-20tYPE
in
the 4/20mA output sub-menu and press
(
to reveal
the existing setting
totAL
or
rAtE
. The function can
be changed by pressing the
&
or
*
push button
followed by the
)
button to return to the
4-20tYPE
prompt in the sub-menu.
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