Siemens SITRANS LUT400, Руководство по эксплуатации

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Page 116 SITRANS LUT400 (HART) – OPERATING INSTRUCTIONS A5E33329501
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• H-flumes come with a flat or sloping floor. The same flow table can be used
because error is less than 1%.
Universal calculation support
When the primary measuring device (PMD) doesn’t fit one of the standard types, it can
be programmed using a universal characterization. When Universal is selected as the
PMD type [
2.15.1. Primary Measuring Device (PMD)
], then both head and flow breakpoints
(
2.15.5. Universal Head vs. Flow
) must be entered to define the flow.
SITRANS LUT400 supports Universal curved (cubic spline) flow calculation shown in the
following chart. (The
2.15.3.1. Method of Flow Calculation
for universal support can be
Ratiometric or Absolute. Refer to your PMD manufacturer’s documentation.)
Typical flow characterization
Characterization is achieved by entering the head and corresponding flow breakpoints,
either from empirical measurement or from the manufacturer's specification. Increasing
the number of defined breakpoints will increase the accuracy of the flow measurement.
Breakpoints should be concentrated in areas exhibiting the higher degrees of non linear
flow. A maximum of 32 breakpoints can be defined, with a minimum of four required. The
curve’s end point is always specified by the parameters
2.15.3.3. Maximum Head
and
2.15.3.4. Maximum Flow at 20 mA
. These two parameter values are in addition to the 32
breakpoints available for definition.
Use as many breakpoints as required by the complexity of your PMD.
See
Volume
on page 73 for more information and parameter
2.15.5. Universal Head vs.
Flow
for characterization.
2.0 18 7.25
2.5 23 9
3.0 28 10.75
4.5 41 16.25
Flume Size
(Diameter in feet)
Point of Measurement
cm inches
Maximums (Max.
Head, Max. Flow)
Curved
Head Breakpoints
Fl
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