BEKA BA337E-SS, Manual

Page: 48 / 65

10.6.2 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 10V with its current being
controlled by the Rate Totaliser. Subject to complying
with intrinsic safety interconnection requirements, the
terminals C1 and C3 may be connected to another
instrument, which will accept a 4/20mA transmitter
input. The 4/20mA current output may also be
transferred to the safe area via a galvanic isolator or
Zener barriers. Terminals C2 and C4 are internally
linked and may be used for joining a return 4/20mA
wire.
Fig 22 shows how a 2-channel Zener barrier may be
used to transfer the 4/20mA current output into the
safe area, alternatively a galvanic isolator may be
used.
Fig 22 Application of 4/20mA output
10.6.3 Configuration
When a Tate Totaliser is supplied with an optional
4/20mA output the configuration menu is extended as
shown in Fig 23. The 4/20mA output sub-menu is
accessed via the
4-20 oP
function that is located
before the
Clr . Gtot
function.
The 4/20mA output may be controlled by the Rate
Totalisers rate or total display, the values
corresponding to 4 and 20mA output are defined in
the sub-menu.
Fig 23 4/20mA output configuration sub-menu
10.6.4 Access 4/20mA output sub-menu:
4-20 oP
Access the Rate Totaliser configuration menu is
described in section 6.2. Using the
&
and
*
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 23.
10.6.5 Enable 4/20mA output:
EnbL
This function allows the 4/20mA output to be
disabled or enabled without altering any of the
4/20mA output parameters. 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.
Note: When the 4/20mA output is disabled by
selecting
oFF
, the output is a constant
3.5mA irrespective of the instrument
display.
10.6.6 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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