Partlow MRC 7800, Инструкция по установке, монтажу и эксплуатации.

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3 STAGE SQUARE ROOT EXTRACTION - EuPA = 3
This approach is used to further minimize the process value below a 1% input, since it is even
less meaningful. Below 1% a low gain linear function is applied. Between 1% and 2.5% a
higher gain linear function is applied. Above 2.5% the square root function applies, as the
sensor begins to provide a reasonably accurate and repeatable output. Refer to the glossary
(page 53).
VARIABLE EXPONENT - EuPA = 4
Open channel flow is used in wastewater and other applications. For rectangular weirs, the
flow is proportional to the height/head to the 3/2 power. For triangular (or V notch) weirs, the
flow is proportional to the height/head to the 5/2 power. For Parshall flumes, the flow is
proportional to the height/head to approximately the 3/2 power. See Table 3-1. When
variable exponent is selected in the Program mode, Engineering Units Exponent, EuE , must
be set for the correct exponent value.
TABLE 3-1
The exponent for a number of common Parshall flumes are as follows:
1 - inch = 1.55
2 - inch = 1.55
3 - inch = 1.547
6 - inch = 1.58
9 - inch = 1.53
1 to 8 ft = 1.522w raised to the .023 power
10 to 50 ft = 1.6
w = throat width in feet
PIECEWISE LINEAR - EuPA = 5
For some applications, the relationship between the input and process value cannot be
specified by one of the available algorithms. For these instances, the relationship can be
approximated by a straight line relationship over portions of the span. Provided enough
pieces, this method will provide the required accuracy. When piecewise linear is selected, the
second set of Engineering Units parameters, Euu2 and EuL2 must be used to specify the
span of the input, and then iu1 , iu2 .... iu20 and Pu1 , Pu2 ..... Pu20 are the input and process
values for the respective points, in engineering units.
VARIABLE EXPONENT WITH CORRECTION - EuPA = 6
For some applications, the relationship between the input and process value can be basically
characterized as exponential, but not to within the accuracy desired. Use of the Piecewise
Linear algorithm may require a large number of points to provide the desired accuracy. By
using the piecewise linear method to provide a correction to the simple exponential, a high
degree of accuracy can be achieved. This is especially applicable to open channel flow using
Palmer-Bowlus flumes or H flumes. Consult factory for assitance, if needed, when using
variable exponent with correction.
SATURATED STEAM FLOW WITH PRESSURE CORRECTION - EuPA = 7
Only available with a 2 Pen unit. For saturated steam flow, accurate flow measurement is
dependent on pressure correction. By using the second pen to input and record pressure, the
pressure data is available to correct the flow value. The input is typically gauge pressure,
which is converted to absolute pressure by the instrument. Since the pressure may be in the
60 PSIG range, barometric pressure or elevation can induce an error. Therefore, the baro-
metric pressure, bAro , needs to be set in the Alarm Set mode. If the input is absolute
pressure, bAro must be set ot zero.