3
1. DESCRIPTION
The BA474ND is a field mounting, Type n certified
4/20mA loop powered temperature transmitter with a
certified galvanically isolated intrinsically safe sensor
input and a large easy to read display. The
instrument, which is HARTenabled, may be
conditioned on-site to operate with most common
thermocouples and resistance thermometers and will
provide a linear 4/20mA output proportional to
temperature, plus a digital temperature display.
Voltage and resistance inputs may be scaled allowing
the BA474ND to display variables other than
temperature such as position and weight.
Optional factory fitted alarms provide two galvanically
isolated solid state outputs that may be
independently configured for high or low operation.
For installation in poorly illuminated areas, an
optional factory fitted loop powered display backlight
is available.
The BA474ND has been ATEX certified Ex nA with
an intrinsically safe Ex [ia] sensor input by European
Notified Body Intertek Testing and Certification Ltd
(ITS). The transmitter complies with the ATEX
Directive 94/9/EC for installation in Zone 2 explosive
gas atmospheres. The certified galvanically isolated
intrinsically safe input allows the transmitter to be
directly connected to sensors in Zone 0 & 1 without
the need for Zener barriers or galvanic isolators.
The transmitter is also ATEX certified Ex tD for use in
combustible dust atmospheres - see Appendix 1.
For international applications the BA474ND has
IECEx Ex nA & nL gas certification and Ex tD dust
certification. The sensor input has been certified
intrinsically safe Ex [ia] and [iaD] – see Appendix 2.
Fig 1 Simplified block diagram
2. DOCUMENTATION
This instruction manual describes the installation and
configuration of the BA474ND Indicating
Temperature Transmitter for ATEX Type nA
applications in gas atmospheres. System design
information for IECEx installations and for use in
combustible dust atmospheres is contained in
appendices to this manual.
The transmitter is HART Registered and is compliant
with HART protocol standard revision 7. HART
commissioning information is included in the
BA47X/67X Indicating Temperature Transmitter
HARTInterface Guide which may be downloaded
from www.beka.co.uk/manuals
3. OPERATION
Fig 1 shows a simplified diagram of the BA474ND
Indicating Temperature Transmitter. The input,
which may be from a resistance thermometer,
thermocouple, or a dc voltage or resistance, is
digitised and transferred to the instrument processor
via an optical isolator. The processor linearises the
input signal, displays the resulting temperature in the
selected units of measurement and controls the
4/20mA output current.
3.1 Controls
All functions of the transmitter may be configured via
the four push buttons which are located behind the
removable switch cover – see Fig 5. For applications
where frequent adjustments are required the
BA474ND transmitter is available with an optional
external membrane keypad. Buttons respond within
0.5 seconds of being operated and unless
continuously pushed the transmitter display will return
to the operating mode after 2 seconds.
In the operational mode, i.e. when the transmitter is
displaying the input signal, these push buttons have
the following functions:
Button Function
While this button is operated the transmitter
will show the display corresponding to 4mA
output.
▲While this button is operated the transmitter
will show the display corresponding to
20mA output.
+Transmitter displays output current in mA
followed by output as % of the range.
P + Transmitter displays HARTshort address
followed by firmware version number.
P + EEntry to configuration menu.
When fitted with optional alarms
P + Entry to alarm set point menu. See 10.4.12
E + Transmitter displays alarm 1 setpoint
E + Transmitter displays alarm 2 setpoint
P Activated alarm reverts to the non-alarm
condition for the configured alarm silence
time. See 10.4.11
