BEKA BA304ND User manual

issue: 8
4th March 2014
BA304ND
Type nL certified
loop-powered
3½ digit field
mounting indicator
issue: 8
Only for replacement use after May 2013.
Use BA304NE for new applications

2
1. Description
2. Operation
3. Type 'nL' certification
3.1 Certificate of Conformity
3.2 ATEX certification
3.3 4/20mA input terminals
3.4 Zones, gas groups and T ratings
3.5 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 Units of measurement & instrument
identification.
8.2 Internal calibrator
8.3 Root extractor
8.3.1 Calibration example with root
extractor.
8.4 Display backlights
8.4.1 Separately powered backlight
8.4.2 Loop powered backlight
8.5 Pipe mounting kits
8.6 Stem mounting kit
CONTENTS
The BA304ND is CE marked to show compliance with the European Explosive Atmospheres
Directive 94/9/EC and the European EMC Directive 2004/108/EC

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1. DESCRIPTION
The BA304ND is an Ex nL certified 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. Housed in a robust IP66 glass
reinforced polyester (GRP) enclosure with an
armoured glass window the BA304ND is suitable
for installation in most industrial environments.
The BA304ND is a third generation instrument
which, although having additional features
including a separate terminal compartment and
ATEX certification, remains functionally compatible
with the original BA304N and BA304NC.
The main application of the BA304ND is to display
a measured variable or control signal in a Zone 2
hazardous 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 BA304ND complies with the European ATEX
Directive 94/9/EC for Group II, Category 3G
equipment.
2. OPERATION
Fig 1 shows a simplified block diagram of a
BA304ND. 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 BA304ND
3. TYPE 'nL' CERTIFICATION
3.1 Certificate of Conformity
ITS Testing and Certification Ltd. (formerly ERA
Technology Ltd) has issued a Certificate of
Conformity Ex99Y4003 confirming that the
BA304ND complies with the CENELEC standard
BS EN50021:1999. This European standard
defines the requirements for the construction,
testing and marking of Group II electrical
apparatus with type of protection 'nL' intended for
use in Zone 2, where an explosive atmosphere of
gas is unlikely to occur, or if it does occur will be
infrequent or remain for short periods only.
3.2 ATEX certification
The BA304ND 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 an EC Declaration of
Conformity BEKA00ATEX0010 has been issued.
The instrument bears 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 which conform
with BS EN60079:Part 14 Electrical Installation in
Hazardous Areas. When designing systems for
installation outside the UK, the local Code of
Practice should be consulted.

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3.3 4/20mA input terminals
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
(Ii) does not exceed 30mA dc.
3.4 Zones, gas groups and T rating
The BA304ND has been certified as Group II,
Category 3G Ex nL IIC T5 apparatus with a Tamb
of -20 to 60°C.
'L' indicates that the BA304ND uses an energy-
limiting technique to achieve compliance as
defined by EN 60079-15. This technique is based
on the philosophy of intrinsic safety which limits the
current and voltage applied to components which
may generate a spark in normal operation. e.g.
switches and potentiometers.
These approvals confirm that the BA304ND is 'safe
in normal operation' and may be:
Installed in a Zone 2 hazardous area
Used at ambient temperatures between
-20 and +60°C
Used with gases in groups:
Group A propane
Group B ethylene
Group C hydrogen
Used with gases having a temperature
classification of:
T1 450°C
T2 300°C
T3 200°C
T4 135°C
or T5 100°C
This allows the BA304ND indicator to be installed
in Zone 2 low risk hazardous areas, and to be
used with most common industrial gases.
3.5 Certification Label Information
Certification information is shown on a label fitted
in a recess on the top outer surface of the
enclosure. The instrument serial number and date
of manufacture are shown on a separate label
inside the terminal compartment.
4. SYSTEM DESIGN FOR ZONE 2
4.1 Transmitter loops
A BA304ND indicator may be connected in series
with almost any 4/20mA current loop and
calibrated to display the measured variable or
control signal in engineering units.
Fig 2 illustrates a typical application in which a
BA304ND indicator is connected in series with a 2-
wire transmitter and controller.
Fig 2 BA304ND in a transmitter loop

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There are two basic design requirements:
1. In normal operation the voltage and
current applied to terminals 1 and 3 of the
BA304ND must not exceed:
Ui = 4V dc
Ii = 30 mA dc
Providing the maximum input current in
normal operation is less than 30mA, the
maximum voltage between the indicator
terminals will automatically be limited by
the internal safety components.
2. The 4/20mA loop must be able to tolerate
the additional 1.1V required to operate the
indicator.
In practice it is only necessary to ensure that in
normal operation the maximum current flowing in
the loop is less than 30mA. In the example shown
in Fig 2 this current is determined by the maximum
current from the transmitter.
The sum of the maximum voltage drops of all the
components in the loop must be less than the
minimum power supply voltage. Considering the
example shown in Fig 2:
Minimum operating voltage of 2-wire Tx 10.0
Maximum voltage drop caused by controller 5.0
Maximum voltage drop caused by BA304ND 1.1
Maximum voltage drop caused by cables 0.4
_____
16.5V
Therefore at 20mA the power supply in this
example must have an output greater than 16.5V
4.2 Remote indication
A BA304ND indicator may be driven from any
4/20mA signal to provide remote indication. Fig 3
shows a typical application in which the output
from a gas analyser drives a BA304ND. Again it is
necessary to ensure that the loop complies with
the two design requirements listed in section 4.1
Fig 3 Remote indication
5. INSTALLATION
5.1 Location
The BA304ND indicator is housed in a robust IP66
glass reinforced polyester (GRP) enclosure
incorporating an armoured glass window and
stainless steel fittings. This makes it suitable for
exterior mounting in most industrial applications,
including off-shore and waste water treatment.
Please contact BEKA associates if high vibration is
anticipated.
The BA304ND is surface mounting, but may be
pipe or stem mounted using the accessory kits
described in sections 8.5 and 8.6 of this manual.
The field terminals and the two enclosure mounting
holes are located in a separate compartment with
a sealed cover allowing the instrument to be
installed without exposing the display assembly or
controls. 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. The BA304ND earth terminal is
connected to the internal EMC filters. For
maximum radio frequency interference rejection
this terminal should be connected to a local earth,
or to an earthed cable screen. To prevent
circulating currents, cable screens should only be
earthed at one point in the safe area.
The BA304ND enclosure is supplied with a
bonding plate to ensure electrical continuity
between the three conduit / cable entries.

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5.2 Installation Procedure
Fig 4 illustrates the instrument installation
procedure.
a. Remove the instrument terminal cover by
unscrewing the two captive 'A' screws.
b. Mount the instrument on a flat surface and
secure with M6 screws through the two 'B'
holes. Alternatively use one of the pipe or
stem mounting kits described in sections
8.5 and 8.6
c. Remove the temporary hole plug and
install an Ex n or Ex e cable gland or
conduit entry. If more than one entry is
required, replace one or both IP66
stopping plugs with an Ex n or Ex e cable
gland or conduit entry.
d. Connect the field wiring to the terminals as
shown in Fig 5.
f. Ensure that the instrument terminal cover
sealing gasket is undamaged and free
from dirt and foreign bodies. Replace the
terminal cover and tighten the two 'A'
screws.
Fig 4 BA304ND installation procedure
5.3 EMC
The BA304ND complies with the requirements of
the European EMC Directive 2004/108/EC. For
specified immunity all wiring should be in screened
twisted pairs.
Fig 5 Dimensions and terminal connections
6. CALIBRATION
The BA304ND 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 indicator is conditioned and calibrated by plug-
in links and two multi-turn potentiometers located
behind the control cover which is secured by two
'C' screws - see Figs 4 & 6.
CAUTION!
The plug-in links and the two
potentiometers are energy limited and
will not cause ignition in normal
operation. Ex 'n' certification requires
that the instrument enclosure provides
IP54 protection, the control cover may
therefore only be removed for calibration
when there is no possibility of dust or
water ingress. Before replacing the
cover ensure that the sealing gasket is
undamaged and free from dirt and
foreign bodies.

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For maximum accuracy, the instrument should
be calibrated using an external traceable
current source with a resolution of at least 4µA.
However, when verification is not required, the
instrument may be fitted with an optional
internal calibrator which allows rapid calibration
without the need for external instruments or
disconnec-tion from the 4/20mA input current.
See section 8.2 for details.
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.
Position of Instrument span
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 decimal point is determined by the position of
the decimal point plug-in 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 BA304ND display increases as the
input current increases, but this can be reversed.
Please contact BEKA associates for details.
6.5 Calibration example
The BA304ND 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 BA304ND 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 between
the two least significant digits,
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 BA304ND will
produce accurate readings outside the 4/20mA
current range. Although not guaranteed, most
BA304ND indicators will operate between 3 and
25mA.

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Fig 6 Position of plug-in links and potentiometers shown with control cover removed

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7. MAINTENANCE
7.1 Fault finding during commissioning
If the BA304ND fails to function during
commissioning the following procedure should be
followed:
Symptom Cause Solution
No display Incorrect There should be 1V
wiring. between terminals 1 &
3 with terminal 1
positive.
(5V between terminals
1 & 13 if a loop
powered backlight
is fitted).
No display Incorrect Check that a current
and no volts wiring or is flowing in the loop.
between no power
terminals 1 supply.
and 3.
Insufficient Check supply voltage
loop and voltage drops
voltage to caused by all
operate components in the loop.
BA304ND.
BA304ND Positive The BA304ND has
displays 1 over-range. been incorrectly
calibrated & is trying to
display a number
greater than 1999.
BA304ND Negative The BA304ND has
displays -1 over-range. been incorrectly
calibrated & is trying to
display a number
less than -1999.
Unstable 4/20mA Check loop supply
display input has a voltage.
large ripple.
7.2 Fault finding after commissioning
CAUTION!
ENSURE PLANT SAFETY BEFORE
STARTING MAINTENANCE
Live maintenance should only be
performed when there is no risk of a
flammable atmosphere being present,
and dust or water can not enter the
enclosure. Before replacing control &
terminal covers ensure that the sealing
gaskets are undamaged and free from
dirt and foreign bodies.
If a BA304ND fails after it has been functioning
correctly, the following table may help to identify
the cause of the failure.
Symptom Cause Solution
No display No power Check that a current
and no volts supply. is flowing in the
between loop.
terminals 1
and 3.
Unstable 4/20mA Check loop supply
display. input has a voltage.
large ripple.
If this procedure does not reveal the cause of the
fault, it is recommended that the instrument is
replaced.
7.3 Servicing
CAUTION!
ENSURE PLANT SAFETY BEFORE
STARTING MAINTENANCE
Live maintenance should only be
performed when there is no risk of a
flammable atmosphere being present,
and dust or water can not enter the
enclosure. Before replacing control &
terminal covers ensure that the sealing
gaskets are undamaged and free from
dirt and foreign bodies.
We recommend that faulty instruments and
instrument assemblies are returned to BEKA
associates or to your local agent for repair.
7.4 Routine maintenance
The mechanical condition of the instrument and
electrical calibration should be regularly checked.
The interval between inspections depends upon
environmental conditions. We recommend that
initially instrument calibration should be checked
annually.

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7.5 Guarantee
Indicators which fail within the guarantee period
should be returned to BEKA associates or our local
agent. It is helpful if a brief description of the fault
symptoms is provided.
7.6 Customer comments
BEKA associates is always pleased to receive
comments from customers about our products and
services. All communications are acknowledged
and whenever possible, suggestions are
implemented.
8. ACCESSORIES
8.1 Units of measurement and instrument
identification
All BA304ND indicators are fitted with a blank
escutcheon around the liquid crystal display. This
escutcheon can be supplied printed with any units
of measurement and tag information specified at
the time of ordering. Alternatively the information
may be added on-site via an embossed strip, dry
transfer or a permanent marker.
CAUTION!
The enclosure should only be dismantled
when the instrument is de-energised, or
there is no risk of a flammable
atmosphere being present. Dust or
water must be prevented from entering
the enclo-sure. Before replacing the
control & terminal covers ensure that the
sealing gaskets are undamaged and free
from dirt and foreign bodies.
To gain access to the display label remove the
terminal cover by unscrewing the two 'A' screws
which will reveal two concealed 'D' screws.
Unscrew the four 'D' screws and carefully lift off the
front of the instrument enclosure - Fig 4 shows the
location of these screws. Add the required legend
to the display label, or replace with a new pre-
printed self-adhesive label which may be obtained
from BEKA associates. Before reassembling
ensure that the sealing gaskets are undamaged
and free from dirt and foreign bodies.
The BA304ND can also be supplied with a blank or
custom engraved stainless steel plate secured to
the front of the instrument by two screws.
8.2 Internal Calibrator
The BA304ND can be supplied with an optional
internal calibrator which simulates 4 and 20mA
input currents. This allows rapid calibration without
the need for external instruments or disconnection
from the 4/20mA input current, but it is not a
substitute for calibration with a traceable external
current source. Fig 6 shows the position of the
calibrator link which is located behind the
instrument control cover.
The plug-in root / linear link shown in Fig 6 must
always be in the root position when an internal
calibrator is fitted. An internal calibrator can not be
fitted to an instrument with a root extractor.

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When using the internal calibrator, the following
procedure should be followed. The adjustments
may be performed with any input current between
4 and 20mA.
Step 1 Put the suppression / elevation, zero,
span and decimal point links in the
required position. Put the root / linear
link in the root position.
Step 2 Put the calibrator link in the 4mA
position and adjust the indicator zero
potentiometer to give the required
display at 4mA.
Step 3 Put the calibrator link in the 20mA
position and adjust the indicator span
potentiometer to give the required
display at 20mA.
Step 4 Repeat steps 2 and 3 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.
Step 5 Return the calibrator link to the
'indicate' position. The indicator will
now respond to the 4/20mA input
current with the revised calibration.
8.3 Root extractor
The BA304ND can be supplied with a square root
extractor which enables the indicator to accurately
display the output from a differential flow meter in
linear engineering units between 10 and 100% of
full flow (4.16 to 20mA). The lineariser continues
to operate with reduced accuracy down to 2.5% of
maximum flow, alternatively clip-off can be
selected which will force the display to zero at
flows below 5% (4.04mA). The location of the clip-
off link is shown in Fig 7. Access to the link is
gained by carefully removing the indicator
assembly from the enclosure as follows. Remove
the terminal cover by unscrewing the two ‘A’
screws which will reveal two concealed ‘D’ screws.
Unscrew the four ‘D’ screws and carefully lift off
the front of the instrument enclosure. Fig 4 shows
the location of these screws. Finally remove
screws securing the electronic assembly.
Fig 7 Location of root extractor clip-off link
When calibrating a BA304ND fitted with a root
extractor the indicator zero potentiometer should
be adjusted to give the required display at 10% of
flow (4.16mA). The indicator zero potentiometer
should not be used to set the display to zero with a
4mA input. Zero suppression or elevation may not
be used, i.e. 4mA must correspond to zero flow.
For reference, the following table shows the output
current from a non-linearised differential flowmeter.
% of full flow Current output mA
2.5 4.01
10.0 4.16
25.0 5.00
50.0 8.00
75.0 13.00
100.0 20.00
A root extractor can not be fitted to an instrument
with an internal calibrator.
8.3.1 Calibration example with root extractor
The BA304ND is required to display rate of flow in
gallons per minute, with a resolution of 0.1 gallons.
The differential flowmeter has an output of 20mA
at a flow rate of 140.0 gallons per minute

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i.e. A span of 1400 ignoring the decimal
point A decimal point in position 00.0
The following adjustments are required:
Step 1 Put the suppression / elevation links
in the elevation position.
Step 2 Put the zero link in the 0 to 500
position.
Step 3 The required span is 1400, therefore
the span links should be placed in the
1000 to 1500 position.
Step 4 The decimal point is required between
the two least significant digits,
therefore the decimal point link should
be placed in the 00.0 position.
Step 5 With 4.160mA input current adjust the
zero potentiometer until the indicator
displays 14.0 (10% of flow). If there is
insufficient adjustment to achieve this,
put the elevation/suppression links in
the suppression position and repeat
step 5.
Step 6 With 20.000mA input current adjust
the span potentiometer until the
indicator displays 140.0
Step 7 Repeat steps 5 and 6 until both
calibration points are correct.
8.4 Display backlights
The BA304ND may be supplied with two different
backlights. The loop powered backlight produces
green background illumination enabling the display
to be read at night and in poor lighting conditions.
No additional power supply or field wiring are
required, but the indicator voltage drop is
increased. Alternatively, the separatly powered
backlight has a bright orange output which
enhances daylight viewing, but additional field
wiring and a power supply are required.
8.4.1 Separately powered backlight
The separately powered backlight is electrically
segregated from the measuring circuit, and has
been certified as a separate Ex nL Group II,
Category 3G circuit.
The Type nL input safety parameters are:
Ui = 30V dc
Ii = 100mA dc
Pi = 1.3W
This allows the backlight to be powered from a
safe area 18 to 30V dc supply as shown in Fig 8.
Providing the supply voltage is less than 30V dc,
the backlight safety components will ensure that
the maximum input current and power are within
the safety limits.
Reducing the supply voltage below 18V, or fitting a
current limiting resistor in series with the supply will
reduce the display brilliance.
Fig 8 Separately powered backlight
8.4.2 Loop powered backlight
This backlight is connected in series with the
4/20mA measuring circuit as shown in Fig 9. In
normal operation the voltage and current applied to
terminals 1 and 13 of the BA304ND must not
exceed:
Ui = 6V dc
Ii = 30 mA dc
Providing the maximum input current in normal
operation is less than 30mA, the maximum voltage
between the indicator terminals will automatically
be limited by the internal safety components.

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Fig 9 Loop powered backlight
8.5 Pipe mounting kits
Two pipe mounting kits are available for securing
the BA304ND to a horizontal or vertical pipe.
Detailed assembly instructions are supplied with
each kit.
BA392D Stainless steel bracket secured by
two worm drive hose clips. Will clamp
to any pipe with an outside diameter
between 60 and 80mm.
BA393D Heavy duty stainless steel bracket
secured by a 'V' bolt. Will clamp to
any pipe with an outside diameter
between 40 and 80mm.
8.6 Stem mounting kit
The BA395 stem mounting kit comprises a
stainless steel bracket which bolts to the rear of
the indicator enclosure enabling the indicator to be
mounted directly onto a flowmeter.