BEKA BA364G, Руководство пользователя

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9.5 4/20mA output
The BA367NE Counters can be supplied with a
factory fitted isolated 4/20mA output which may be
configured to represent the rate or total display.
Note: Only one of the three output options can be
fitted.
9.5.1 Ex nA certification
The optional 4/20mA output is a separate
galvanically isolated Ex nA circuit with the following
input parameters:
Ui = 30V dc
This allows the 4/20mA output to be connected to
any dc circuit providing that in normal operation the
maximum supply voltage is not greater than 30V dc.
Providing that the BA367NE Counter is correctly
installed in a panel enclosure located in Zone 2
complying with the requirements for Ex n protection,
the 4/20mA current output may be used to transmit
to suitably protected equipment located in Zone 1 or
2 of a hazardous area, or to equipment located in a
safe area.
Fig 19 Application of 4/20mA output
(Shown without recommended screened cables)
Fig 19 shows a typical application in which a
BA367NE Counter mounted in an Ex n panel
enclosure located in Zone 2 is retransmitting the
4/20mA current to the safe area.
To comply with the requirements of EN 60079-14
Electrical installations design, selection and erection ,
each of the wires entering the hazardous area
should be individually fused and contain a means of
isolation. These two requirements may be satisfied
by installing DIN rail mounted terminals incorporating
a fuse which can easily be opened as shown in Fig 2
to provide isolation. Clear identification of, and easy
access to the means of isolation is essential for their
effective use. It is also necessary to ensure that the
maintenance procedure makes sure that
unauthorised re-closure of the switches does not
occur. It is not considered necessary to have a
means of isolation or electrical protection for cable
screens.
For some application Ex nA instrumentation
energised by a current limited power supply or
instrument that can be switched off, is often
considered adequate and to comply with the
requirements of the standard.
9.5.2 Configuration
When a BA367NE Counter is supplied with an
optional 4/20mA output the configuration menu is
extended as shown in Fig 20. 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 20 4/20mA output configuration sub-menu
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