4
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
