Measurement Response; Damping; Loss Of Echo (Loe) - Siemens SITRANS LR250 Operating Instructions Manual

Measurement Response

Note: Units are defined in Unit (2.3.1.) and are in meters by default.
Response Rate (2.3.8.1.) 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.
Changing Response Rate resets Fill Rate per Minute (2.3.8.2.), Empty Rate per
Note:
Minute (2.3.8.3.), and Shots (2.5.6.).
Response Rate
(2.3.8.1.)
* Slow
Medium
Fast

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

Loss of Echo (LOE)

A loss of echo (LOE) occurs when the calculated measurement is judged to be unreliable
because the echo confidence value has dropped below the echo confidence threshold.
Confidence (2.5.9.1.) describes the quality of an echo. HIgher values represent higher
quality.
Echo Threshold (2.5.7.3.) defines the minimum confidence value required for an echo to be
accepted as valid and evaluated.
If the LOE condition persists beyond the time limit set in Loss of Echo (LOE) Timer (2.3.6.)
the LCD displays the Service Required icon, and the text region displays the fault code
S: 0 and the text LOE.
Page 150 SITRANS LR250 (FF) – OPERATING INSTRUCTIONS
Fill Rate per Minute (2.3.8.2.)/
Empty Rate per Minute (2.3.8.3.)
0.1 m/min (0.32 ft/min)
1.0 m/min (3.28 ft/min)
10.0 m/min (32.8 ft/min)
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
1
Shots (2.5.6.)
2 3 4 5 6
input (level) smoothed output
Series1 Series2
25
10
5
Time (s)
7
7ML19985KL01