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1. DESCRIPTION
The BA307C and BA308C are intrinsically safe
loop powered 3½ digit indicators that display the
current flowing in a 4/20mA loop in engineering
units. Both instruments introduce less than a 1.1V
drop which allows them to be installed into almost
any 4/20mA current loop. No additional power
supply or battery is required.
The two indicators are electrically similar, but have
different size displays and enclosures.
Model Display height Bezel size
BA307C
12.7mm
96 x 48mm
BA308C
25.4mm
144 x 72mm
The main application of the BA307C and BA308C
is to display a measured variable or control signal
in a hazardous process area. The zero and span
of the display are independently adjustable so that
the indicators can be calibrated to display any
variable represented by the 4/20mA current, e.g.
temperature, flow, pressure or level.
The BA307C and BA308C have been certified
intrinsically safe for use in gas hazardous areas by
Notified Body Intertek Testing and Certification Ltd
which has been used to confirm compliance with
the European ATEX Directive 94/9/EC. The
EC-Type Examination certificate specifies that
under fault conditions the output voltage, current
and power at the 4/20mA input terminals will not
exceed those specified for
simple apparatus
in
Clause 5.7 of EN 60079-11, which simplifies
installation and documentation.
The BA307C and BA308C are also FM approved
for use in the USA and cFM approved for use in
Canada, these approvals are described in
Appendix 1.
International IECEx certification is described in
Appendix 2.
2. OPERATION
Fig 1 shows a simplified block diagram of both
models. The 4/20mA input current flows through
resistor R1 and forward biased diode D1. The
voltage developed across D1, which is relatively
constant, is multiplied by a switch mode power
supply and used to power the analogue to digital
converter and liquid crystal display. The voltage
developed across R1, which is proportional to the
4/20mA input current, provides the input signal for
the analogue to digital converter.
Fig 1 Simplified block diagram of BA307C
and BA308C
3. INTRINSIC SAFETY CERTIFICATION
3.1 ATEX certificate
The BA307C and BA308C were issued with an
EC-Type Examination Certificate number
ITS02ATEX2027 by Notified Body ITS Testing and
Certification Ltd. This confirmed compliance with
European ATEX standards for Group II, Category
1G equipment, EEx ia IIC T5 at the time of
certification. Please see the BEKA product
Declaration of Conformity for confirmation of
compliance with current harmonised ATEX
standards. Both indicators carry the Community
Mark and, subject to local codes of practice, may
be installed in any of the European Economic Area
(EEA) member countries. ATEX certificates are
also acceptable for installations in Switzerland.
This manual describes installations that conform
with EN 60079: Part 14 Electrical Installations
design, selection and erection in hazardous areas.
When designing systems for installation outside
the UK, the local Code of Practice should be
consulted.
