Appendix A: Technical References; Principles Of Operation; Measurement Response; Echo Lock - Siemens Sitrans PROBE LU Instruction Manual

Appendix A: Technical References

Principles of operation

The transducer emits a series of ultrasonic pulses: each pulse is reflected as an echo
from the material and sensed by the transducer. The echo is processed by
SITRANS Probe LU, using Siemens proven Sonic Intelligence techniques. Filtering is
applied to help discriminate between the true echo from the material and false echoes
from acoustic and electrical noise, and agitator blades in motion.
The time for the pulse to travel to the material and back is temperature-compensated,
and then converted into distance for display, and a cyclic value for PROFIBUS PA output.

Measurement Response

The measurement response (response rate) limits the maximum rate at which the
display and output respond to changes in the measurement. Once the real process fill/
empty rate (m/s) is established, a response rate can be selected that is slightly higher
than the application rate. The response rate automatically adjusts the filters that affect
the output response rate.
There are three preset options: slow, medium, and fast.
Related
Parameters
Values
If none of the preset options is satisfactory, the filters can be adjusted individually.

Echo Lock

When the echoes are received, the relevant echo algorithm is applied to determine the
true material echo. If the selected echo is within the window, the window is then
centered about the echo. Otherwise the window widens with each successive shot until
the selected echo is within the window, which then returns to its normal width.
Echo Lock selects the measurement verification process:
Values
7ML19985JB02 SITRANS Probe LU (PROFIBUS PA) – INSTRUCTION MANUAL
Response LOE Timer
Rate (minutes)
1 * slow 100
2 medium 10
3 fast 1
0
Off
1
Maximum Verification
2 *
Material Agitator
3
Total Lock
Empty
Fill Rate
Rate
0.1 m/minute 0.1 m/minute
1 m/minute 1 m/minute
10 m/minute 10 m/minute
Echo
Lock
material
2
agitator
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