User's Manual
Table Of Contents
- 8 Parameter reference
- 9 Service and maintenance
- 10 Diagnosing and troubleshooting
- 11 Technical data
- 12 Dimension drawings
- 12.1 Threaded horn antenna
- 12.2 Threaded horn antenna with extension
- 12.3 Flanged horn antenna
- 12.4 Flanged horn antenna with extension
- 12.5 Flanged encapsulated antenna (2"/DN50/50A sizes only)
- 12.6 Flanged encapsulated antenna (3"/DN80/80A sizes and larger)
- 12.7 Threaded PVDF antenna
- 12.8 Threaded connection markings
- 12.9 Raised-Face flange per EN 1092-1 for flanged horn antenna
- 12.10 Raised-Face flange per EN 1092-1 for flanged encapsulated antenna
- 12.11 Flat-Face flange
- 12.12 Process connection tag (pressure rated versions)
- A Appendix A: Technical reference
- B Appendix B: Communications via Foundation Fieldbus
- C Appendix C: Certificates and support
- 13 List of abbreviations
- 14 LCD menu structure
- Glossary
- Index
Appendix A: Technical reference
A.2 Echo processing
SITRANS LR250 (FOUNDATION FIELDBUS)
238 Operating Instructions, 01/2014, A5E32221411-AB
A.2.8
Measurement Range
Near Range (2.5.1.)
Near Range programs SITRANS LR250 to ignore the zone in front of the antenna. The default
blanking distance is 50 mm (1.97") from the end of the antenna.
Near Range allows you to increase the blanking value from its factory default. But
Auto False
Echo Suppression (2.5.10.1.)
is generally recommended in preference to extending the blanking
distance from factory values.
Far Range (2.5.2.)
Far Range can be used in applications where the base of the vessel is conical or parabolic. A
reliable echo may be available below the vessel empty distance, due to an indirect reflection
path.
Increasing Far Range to 30% or 40% can provide stable empty vessel readings.
A.2.9
Damping
Filter Time Constant (2.6.7.1)
smooths out the response to a sudden change in level. This is an
exponential filter and the engineering unit is always in seconds.
In 5 time constants the output rises exponentially: from 63.2% of the change in the first time
constant, to almost 100% of the change by the end of the 5th time constant.
Damping example
time constant = 2 seconds
input (level) change = 2 m