3. ELECTRICAL SYSTEM DESIGN
A BA578C indicating transmitter will operate from
any voltage between 10 and 30V. When designing
a loop it is therefore necessary to ensure that the
voltage between terminals 5 & 6 is between 10 and
30V at all output currents.
Fig 2 Typical BA578C loop
Considering the temperature measuring loop shown
in Fig 2. The sum of the maximum voltage drops of
all the components in the loop must be less than the
minimum power supply voltage. With an output
current of 20mA:
Minimum operating voltage of BA578C 10.0V
Maximum voltage drop caused by
250ohm load
5.0V
(250ohms x 20mA)
Maximum voltage drop caused by cable 0.2V
resistance (10ohms x 20mA)
-------
Total maximum voltage drop
15.2V
The power supply must therefore have an output
greater than 15.2V
4. INSTALLATION
4.1 Location
The BA578C indicating transmitter is housed in a
robust aluminium enclosure with a polyester front
panel and Noryl bezel. The front panel provides
IP65 protection and a gasket seals the joint
between the instrument and the panel. The
transmitter may be installed in any panel providing
the environmental limits shown in the specification
are not exceeded.
Fig 3 shows the overall dimensions of the BA578C.
The recommended panel cut-outs are as detailed
below
a) DIN 43 700
138.0 +1.0 / -0.0mm
68.0. +0.7 / -0.0mm
b) To achieve IP65 seal between instrument and
panel
136.0 + 0.5 / -0.0mm
66.2 + 0.5 / -0.0mm
Fig 3 BA578C dimensions and panel cut-out
4.2 Installation Procedure
Figs 4a and 4b illustrate the instrument installation
procedure.
a.
Insert the instrument into the panel aperture
from the front of the panel.
b.
Fix two panel mounting clips to opposite sides
of the instrument and tighten until the
instrument is secure.
Four clips will be required to achieve an IP65
seal between the instrument and the panel.
c.
Connect the panel wiring to the rear terminal
block(s) as shown in Fig 4b.
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