Appendix A: Technical reference
A.2 Echo processing
SITRANS LR250 (PROFIBUS PA)
Operating Instructions, 08/2014, A5E32221386-AC
239
Note
Units are defined in Units (2.3.1.)
and are in meters by default.
limits the maximum rate at which the display and output respond to
changes in the measurement. There are three preset options: slow, medium, and fast.
Once the real process fill/empty rate (m/s by default) is established, a response rate can be
selected that is slightly higher than the application rate. Response Rate automatically adjusts the
filters that affect the output response rate.
Fill Rate (2.3.8.2)/Empty Rate (2.3.8.3)
1.0 m/min (3.28 ft.min) 10 s
Damping
Filter Time Constant (2.6.8.1)
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.
time constant = 2 seconds
input (level) change = 2 m
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