Siemens sitrans PROBE LU User Manual

7ML19985JB02 SITRANS Probe LU (PROFIBUS PA) – INSTRUCTION MANUAL Page 39
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A: Technical Reference
Open Channel Monitoring (OCM)
OCM converts a level reading (head) into a flow value using a linear algorithm.
SITRANS Probe LU can convert a head level measurement into a flow rate, using an
eleven breakpoint head-versus-flow characteristic curve. This chart is usually available
from the manufacturer of the v-notch weir, Parshall flume, or other open channel device.
Linearization type must be set to Linearization Table, and up to 32 breakpoints must be set
for head levels and corresponding flowrates (using the Volume tables). Once these
breakpoints are set, the output is scaled to represent the flowrate, and the RUN mode
display will show the flowrate.
Example: Flow Characterization (using 11 breakpoints)
The maximum and minimum points on the curve must be defined. Then program the
remaining breakpoints to closely match the flow curve of your open channel device.
Chemical compatibility
The plastic materials used in the construction of SITRANS Probe LU (ETFE, PBT, PEI, and
PVDF) are resistant to attack from most chemicals. For exposure to specific
environments, check with chemical compatibility charts before installing and operating
SITRANS Probe LU in your application.
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12 3 4 65789
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11
head (level) breakpoints
flow (volume) breakpoints

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)