Siemens sitrans PROBE LU User Manual

7ML19985JB02 SITRANS Probe LU (PROFIBUS PA) – INSTRUCTION MANUAL Page 35
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A: Technical Reference
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.
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:
Related
Parameters
Response
Rate
LOE Timer
(minutes)
Fill Rate
Empty
Rate
Echo
Lock
Values
1* slow 100 0.1 m/minute 0.1 m/minute
2
material
agitator
2 medium 10 1 m/minute 1 m/minute
3 fast 110 m/minute 10 m/minute
Values
0
Off
1
Maximum Verification
2*
Material Agitator
3
Tota l L ock

Siemens sitrans PROBE LU Specifications

General

Measuring Principle	Ultrasonic
Communication	HART
Output	4 to 20 mA
Power Supply	12 to 30 V DC
Process Temperature	-40 to 80 °C
Enclosure Rating	IP68
Material	PVDF
Ambient Temperature	-40 to 70 °C
Measurement Range	0.25 to 12 m (0.8 to 39 ft)