5
Alternatively, the BA354ND may be programmed
so that the total display is reset to zero when the
Up
and
Down
push-buttons are operated
simultaneously.
3.5 Zones, gas groups and T rating
The BA354ND has been certified as Group II,
Category 3G apparatus as defined in the ATEX
Directive and as Ex nL T5, Tamb –20 to 60
o
C.
‘L’ indicates that the BA354ND uses energy-
limiting techniques to achieve compliance as
defined in EN 60079-15. This technique is based
on the philosphy 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 BA354ND is safe
in normal operation and may be installed in:
Zone 2 hazardous area
Be used with gases in groups:
Group A propane
Group B ethylene
Group C hydrogen
Having a temperature classification of:
T1
450°C
T2
300°C
T3
200°C
T4
135°C
or T5
100°C
At an ambient temperatures between –20 and
+60
o
C
This allows the BA354ND to be installed in Zone 2
hazardous areas (low risk) and to be used with
most common industrial gases.
3.6 Certification Label Information
The ATEX certification label is fitted in a recess on
the top outer surface of the enclosure. The year
of manufacture and instrument serial number are
shown on a separate label within the terminal
compartment.
4. SYSTEM DESIGN FOR ZONE 2
4.1 Flow transmitter loops
A BA354ND rate totaliser may be connected in
series with almost any 4/20mA flow loop and
calibrated to display the rate of flow and total flow
in engineering units. Fig 2 illustrates a typical flow
loop application.
There are two basic design requirements:
1. In normal operation the voltage, current and
power applied to terminals 1 and 3 of the
BA354ND must not exceed:
Ui
4V dc
Ii
30mA dc
Providing the maximum input current in
normal operation is less than 30mA, the
maximum input voltage will be automatically
limited to less than 4V by the safety
components within the BA354ND.
2. The 4/20mA loop must be able to tolerate the
additional 1.1V required to operate the
BA354ND.
In practice it is only necessary to ensure that that
in normal operation the maximum current flowing
in the loop is less than 30mA. In the example
shown in Fig 2, the maximum current is
determined by the maximum output from the
flowmeter.
Fig 2 BA354ND in a flow loop
