Open Channel Monitoring (Ocm) - Siemens SITRANS L 7ML5400 Operating Instructions Manual

7.11

Open Channel Monitoring (OCM)

An OCM installation is defined one of three ways, based on the Primary Measuring Device
(PMD):
1. Dimensional
For some common weir and flume types. PMD dimensions (PMD Dimensions (2.15.4.)
(Page 239)) are entered directly.
Vessel Type
BS- 3680 Rectangular Flume (Page 133)
BS- 3680 Round Nose Horizontal Crest Weir (Page 134)
BS- 3680 Trapezoidal Flume (Page 135)
BS- 3680 U-Flume (Page 137)
BS- 3680 Finite Crest Weir (Page 139)
BS- 3680 Thin Plate Rectangular Weir (Page 141)
BS- 3680 Thin Plate V-Notch Weir (Page 143)
Rectangular Weir Contracted (Page 145)
Round Pipe (Page 146)
Palmer Bowlus Flume (Page 147)
H-Flume (Page 148)
2. Exponential
For most other weir and flume types. PMD exponents provided by the manufacturer are
entered. Flow is calculated using the exponent (Flow Exponent (2.15.3.2.) (Page 236)) and
the maximum values (Maximum Head (2.15.3.3.) (Page 237) and Maximum Flow at 20 mA
(2.15.3.4.) (Page 237) at 20 mA).
Vessel Type
Standard Weirs (Page 126)
Parshall Flume (Page 128)
Leopold Lagco Flume (Page 129)
Cut Throat Flume (Page 130)
3. Universal
For all other PMDs, the head-to-flow curve can be plotted based on known breakpoints,
usually supplied by the PMD manufacturer.
Vessel Type
Typical flow characterization (Page 150)
Example flumes (Page 151)
Example weirs (Page 152)
SITRANS LUT400
Operating Instructions, 04/2021, A5E33329501-AG
General Operation
7.11 Open Channel Monitoring (OCM)
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