BEKA BA304NC User manual
Issue: 7
4th March 2014
BA304NC
Type nA
Loop-powered
3½ digit field
mounting indicator
issue 7
2
1. Description
2. Operation
3. Type ‘nA’ Certification
3.1 ATEX Certificate
3.2 Zones, gas groups & T rating
3.3 Input parameters
3.4 Certification label information
4. System Design for Zone 2
4.1 Transmitter loops
4.2 Remote indication
5. Installation
5.1 Location
5.2 Installation procedure
5.3 EMC
6. Calibration
6.1 Zero adjustment
6.2 Span adjustment
6.3 Decimal point
6.4 Reverse action
6.5 Calibration example
6.6 Over and under-range
7. Maintenance
7.1 Fault finding during commissioning
7.2 Fault finding after commissioning
7.3 Servicing
7.4 Routine maintenance
7.5 Guarantee
7.6 Customer comments
8. Accessories
8.1 Engraved scale and tag plates
8.2 Root extractor
8.2.1 Calibration example
8.3 Display backlight
8.4 Pipe mounting kits
8.5 Panel mounting kit
The BA304NC is CE marked to show compliance with the
European Explosive Atmospheres Directive 94/9/EC
and the European EMC Directive 2004/108/EC
CONTENTS
3
1. DESCRIPTION
The BA304NC is an Ex nA (non sparking) loop
powered digital indicator which displays the current
flowing in a 4/20mA loop in engineering units. The
instrument introduces less than a 1.1V drop which
allows it to be installed into almost any 4/20mA
current loop. No additional power supply or battery
is required.
The main application of the BA304NC is to display
a measured variable or control signal in a Zone 2
hazardous process area. The zero and span of
the display are independently adjustable so that
the indicator may be calibrated to display any
variable represented by the 4/20mA current, e.g.
temperature, flow, pressure or level.
The BA304NC has been issued with a Type
Examination Certificate and complies with the
European ATEX Directive for Group II Category
3G equipment.
The indicator is available in a glass reinforced
polyester (GRP), or an epoxy painted aluminium
enclosure. Both provide IP66 protection.
2. OPERATION
Fig 1 shows a simplified block diagram of a
BA304NC. 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 BA304NC
3. TYPE ‘nA’ CERTIFICATION
3.1 ATEX certificate
The BA304NC complies with the European ATEX
Directive 94/9/EC for Group II, Category 3G
equipment. It has been assessed using the
‘Internal Control of Production’ procedure specified
in Annex 8 of the Directive. A technical dossier
has been prepared and a Type Examination
Certificate BEKA03ATEX0015 has been issued.
The instrument carries 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 instruction manual describes installations
which conform with EN 60079:Part 14 Electrical
Installation in Hazardous Areas. When designing
systems for installation outside the UK, the local
Code of Practice should be consulted.
4
3.2 Zones, Gas Groups and T rating
The BA304NC has been certified as Group II,
Category 3G Ex nA nL ia IIC T5 Gc Tamb -40 to
60oC.
Ex nA is a non-sparking technique complying with
the requirements of harmonised standard
EN 60079-15:2010.
Ex nL is an energy-limiting technique complying
with EN 60079-15:2005 which will be de-
harmonised in May 2013. After this date Ex nL
approval will be for legacy purposes only i.e.
replacement & limited extensions.
Ex i code only applies to the potentiometers and
links.
These approval confirm that the BA304NC is safe
in normal operation and may be:
Installed in a Zone 2 hazardous area
At ambient temperatures between
-40 to 60ºC (operating temp –20 to +60ºC).
Used in gase groups:
Group A propane
Group B ethylene
Group C hydrogen
Having a temperature classification of:
T1 450ºC
T2 300ºC
T3 200ºC
T4 135ºC
T5 100ºC
Although certified safe in normal operation at
ambient temperatures between –40 and +60ºC,
the guaranteed operating temperature range of
the BA304NC is –20 to +60ºC.
This allows the BA304NC indicator to be installed
in a Zone 2 low risk hazardous area and to be
used with most common industrial gases except
carbon disulphide and ethyl nitride.
3.3 Input parameters
Input terminals 1 and 3 may be safely connected in
series with any 4/20mA loop providing that in
normal operation the input current to the indicator
does not exceed 100mA and the supply voltage
does not exceed 30V.
3.4 Certification Label Information
The certification information label is fitted on the
top outer surface of the enclosure. It shows the
ATEX certification information plus BEKA
associates name and location.
The instrument serial number and date of
manufacture are shown on a separate label within
the instrument enclosure.
5
4. SYSTEM DESIGN FOR ZONE 2
The BA304NC may be connected in series with
almost any Zone 2 4/20mA current loop and
calibrated to display the measured variable or
control signal in engineering units. There are four
design requirements:
1. The current flowing in the 4/20mA loop, must
not exceed 100mA in normal operation.
2. Wiring must comply with Clause 9 of
EN 60079-14 Electrical installation in
hazardous areas.
3. The instrument enclosure must be fitted with
Ex n or Ex e certified glands, conduit fittings
or blanking plugs.
4. The loop must be able to tolerate the
additional 1.2V required to operate the
indicator.
Fig 2 illustrate a typical application in which an
indicator is connected in series with a 2-wire Ex n
transmitter.
Fig 2 Typical Zone 2 transmitter loop
To strictly 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. However, in
practice instrumentation energised by a current
limited power supply or instrument that can be
switched off is often considered adequate.
4.2 Remote indication
The BA304NC may be driven directly from a safe
area instrument with a 4/20mA output to provide a
remote display within a Zone 2 hazardous area.
There are four design requirements:
1. The current flowing in the 4/20mA loop, must
not exceed 100mA in normal operation.
2. Wiring must comply with Clause 9 of
EN60079-14 Electrical installation in
hazardous areas.
3. The instrument enclosure must be fitted with
Ex n or Ex e certified glands, conduit fittings
or blanking plugs.
4. The safe area 4/20mA output from the safe
area instrument must be able to supply the
1.2V required to operate the indicator.
Fig 3 shows a typical application.
Fig 3 Remote indication in Zone 2 hazardous area
To strictly comply with the requirements of
EN 60079:14 Electrical Installation in Hazardous
Areas, each of the wires entering the hazardous
area should be individually fused and contain a
means of isolation. However, in practice
instrumentation energised by a current limited
6
power supply or instrument that can be switched
off is often considered adequate.
CAUTION !
The enclosure cover should only be
removed when the measuring loop is not
energised, or when there is no risk of a
flammable atmosphere being present and
dust or water can not enter the
enclosure. Before replacing the
enclosure cover ensure that the sealing
gasket is undamaged and that it is free
from dirt and foreign bodies.
Comprehensive design and installation information
for Ex nA [extra low voltage] instrumentation is
contained in the BEKA Application Guide AG310
which may be downloaded from the BEKA website
www.beka.co.uk.
7
5. INSTALLATION
5.1 Location
The BA304NC indicator can be supplied in either a
glass reinforced polyester (GRP), or an epoxy
painted aluminium enclosure. Both provide IP66
protection and have a polycarbonate window and
stainless steel fittings. The GRP enclosure is
suitable for most industrial installations including
off-shore and waste water treatment applications.
For installations where solvents may be present,
the aluminium enclosure provides maximum
protection, but it is not recommended for offshore
applications.
Both enclosures are surface mounting, but may be
pipe or panel mounted using the accessory kits
described in section 8 of this manual.
To simplify installation, the enclosure can be
installed and the field wiring terminated prior to the
indicator assembly being fitted. The enclosure
contains diodes to maintain continuity of the
4/20mA loop when the indicator assembly is not
present. Terminals 2 and 4 are internally joined
and may be used for linking the return 4/20mA wire
- see Fig 2. Similarly, terminals 5 and 6 are
internally joined and may be used for linking the
cable screens. Terminal 7 is internally connected
to an insulated radio frequency screen in the GRP
enclosure, and to the case in the aluminium
enclosure.
5.2 Installation Procedure
Fig 4 illustrates the instrument installation
procedure.
a. Remove the enclosure cover by unscrewing
the four captive 'A' screws.
b. Remove the indicator assembly from the
enclosure by unscrewing the three captive 'B'
screws.
c. Mount the enclosure on a flat surface and
secure with screws or bolts through the four
corner 'C' holes. Alternatively use one of the
pipe or panel mounting kits described in
sections 8.4 and 8.5
d. Remove the temporary hole plug and install
an Ex e or Ex n cable gland or conduit fitting.
If two entries are required, the stopping plug
may be replaced with an Ex e or Ex n cable
gland or conduit fitting.
e. Connect the field wiring to the terminals as
shown in Fig 5.
f. Replace the indicator assembly and evenly
tighten the three 'B' screws.
g. Replace the enclosure cover and evenly
tighten the four 'A' screws.
Fig 4 BA304NC installation procedure
Comprehensive installation information for
Ex nA [extra low voltage] instrumentation is
contained in the BEKA Application Guide AG310
which may be downloaded from the BEKA website
www.beka.co.uk.
8
5.3 EMC
The BA304NC complies with the requirements of
the European EMC Directive 2004/108/EC. For
specified immunity all 4/20mA wiring should be in
screened twisted pairs, with the screen earthed
within the safe area. Terminal 7 should be
connected to a local earth or to a cable screen
which is earthed in the safe area.
Fig 5 Dimensions and terminal connections
9
6. CALIBRATION
The BA304NC will be supplied calibrated as
requested at time of ordering. If calibration is not
requested, the indicator will be set to display 00.0
with 4.000mA input, and 100.0 with 20.000mA
input.
The BA304NC is conditioned and calibrated by
plug-in links and two multi-turn potentiometers.
For maximum accuracy, the instrument should be
calibrated using an external traceable current
source with a resolution of at least 4µA.
Fig 6 Location of calibration links
and potentiometers
6.1 Zero adjustment
Zero is defined as the number displayed by the
indicator with a 4.000mA input current and may be
adjusted between -1000 and 1000. The zero
potentiometer has two ranges, 0 to 500 and 500 to
1000. Zero polarity is defined by the position of
the suppression / elevation links which are shown
in Fig 6.
Suppression / elevation links
Position Display with 4mA input
adjustable between
Elevation 0 and 1000
Suppression 0 and -1000
Zero link
Position Display with 4mA input
adjustable between
0 to 500 0 and 500
500 to 1000 500 to 1000
6.2 Span adjustment
Span is defined as the difference between the
number displayed with 4.000mA input and the
number displayed with 20.000mA input. It is
adjustable between 0 and 1999 in four ranges. Fig
6 shows the position of the span links and the span
potentiometer.
Difference in display
Position with 4 & 20mA input
of span links adjustable between
000 to 500 000 and 500
or 500 to 1000 500 and 1000
or 1000 to 1500 1000 and 1500
or 1500 to 1999 1500 and 1999
6.3 Decimal point
A dummy decimal point may be displayed between
any of the four digits. The position or absence of
this dummy decimal point is determined by the
position of the decimal point link shown in Fig 6.
When calculating the required span and zero
settings the decimal point should be ignored.
6.4 Reverse action
Normally the BA304NC display increases as the
input current increases, but this can be reversed.
Please contact BEKA associates for details.
10
6.5 Calibration example
The BA304NC is required to display:
25.0 with 4.000mA input
115.0 with 20.000mA input
i.e. A zero of positive 250 (Ignoring decimal point)
A span of 900 (Ignoring decimal point)
A decimal point in position 00.0
The following adjustments are required:
Step 1 The BA304NC is required to display a
positive zero therefore the suppression
/ elevation links should be put in the
elevation position.
Step 2 The required zero is 250, therefore the
zero link should be put in the 0 to 500
position.
Step 3 The required span is 900, therefore the
span links should be placed in the 500
to 1000 position.
Step 4 The decimal point is required in front of
the least significant digit, therefore the
decimal point link should be placed in
the 00.0 position.
Step 5 With 4.000mA input adjust the zero
potentiometer until the indicator
displays 25.0
Step 6 With 20.000mA input adjust the span
potentiometer until the indicator
displays 115.0
Step 7 Repeat steps 5 and 6 until both
calibration points are correct. The span
and zero controls are almost
independent so it should only be
necessary to repeat each adjustment
twice.
6.6 Over and under-range
If the indicator display range is exceeded, the three
least significant digits will be blanked. Under-
range is indicated by -1 and over-range by 1. If
the display range is not exceeded, the BA304NC
will produce accurate readings outside the 4/20mA
current range. Although not guaranteed, most
BA304NC indicators will operate between 3 and
25mA.
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