BEKA BA405C, Руководство пользователя

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1. DESCRIPTION
The BA405C is an intrinsically safe loop powered
set point station which enables the current flowing
in a 4/20mA loop to be manually adjusted from
within a hazardous process area.
The main application of the BA405C is the
adjustment of plant parameters. Controller set
points, actuator positions or any variable
represented by a 4/20mA signal may be manually
adjusted.
The BA405C has a high resolution ten turn control
allowing accurate adjustment of the 4/20mA
current and a 3½ digit indicator to display the
4/20mA loop current in any linear engineering
units. Optional separately powered and loop
powered display backlights are available for the
display.
The BA405C and the optional display backlights
comply with the European ATEX Directive 94/9/EC
and have been issued with an EC-Type
Examination certificate by Notified Body ITS
Testing and Certification Ltd.
For use in the USA the BA405C has intrinsic safety
and nonincendive FM Approval - see Appendix 1.
2. OPERATION
This instruction manual describes ATEX system
design and installation, please refer to Appendix 1
for details of the FM Approval.
Fig 1 shows a simplified block diagram of the
BA405C manual set point station. The ten turn
control knob enables the current flowing in the loop
to be manually set at any value between
approximately 3.5 and 21mA. The output
resistance of the BA405C is very high so the loop
current will be unaffected by changes in the supply
voltage.
Caution
The 4/20mA output should not be used for
critical safety applications.
The 3½ digit internal indicator can easily be
calibrated on-site to show the loop current in
engineering units. For example, in an application
where the BA405C is being used to adjust the set
point of a speed controller, the internal indicator
may be calibrated to display the requested speed
in
RPM.
Two types of optional display backlighting are
available. The loop powered backlight produces
green background illumination enabling the display
to be read at night or in poor lighting conditions.
The separately powered backlight has a bright
orange output which enhances daylight viewing.
Fig 1 Simplified block diagram of BA405C
3. INTRINSIC SAFETY CERTIFICATION
3.1 ATEX certificate
The BA405C has been issued with an EC-Type
Examination Certificate ITS03ATEX21103 by
Notified Body Intertek Testing Services (ITS)
confirming compliance with the European ATEX
Directive 94/9/EC for Group II, Category 1 G
apparatus, EEx ia IIC T5. The instrument bears
the Community Mark and, subject to local codes of
practice, may be installed in any of the European
Economic Area (EEA) member countries. ATEX
certificates are also acceptable for installations in
Switzerland. This manual describes installations
which conform with BS EN60079:Part14 Electrical
Installation in Hazardous Areas. When designing
systems for installation outside the UK, the local
Code of Practice should be consulted.
3.2 FM Approval for use in the USA
Please refer to Appendix 1 for information about
FM intrinsic safety and nonincendive approval of
the BA405C
.