BEKA BA574C, Руководство пользователя

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3. ELECTRICAL SYSTEM DESIGN
A BA574C indicating transmitter will operate from
any dc 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 temperature measuring 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 BA574C 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
Therefore the power supply must have an output
greater than 15.2V
4. INSTALLATION
4.1 Location
The BA574C indicating transmitter can be supplied
in either a glass reinforced polyester (GRP), or an
epoxy painted aluminium enclosure. Both provide
IP66 protection and have a toughened glass
window and stainless steel fittings. The GRP
enclosure is suitable for most industrial installations
including off-shore and waste water treatment
applications. For installations where solvents may
be present, the aluminium enclosure provides
maximum protection.
Fig 3 BA574C installation procedure
Both enclosures are surface mounting, but can be
pipe or panel mounted using the accessory kits
described in section 9.
To simplify installation, the enclosure may be
installed and the field wiring terminated prior to the
transmitter assembly being fitted. Terminal 7 is
internally connected to the radio frequency screen
in the GRP enclosure and to the case in the
aluminium enclosure .
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