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2150EX Area Velocity Flow Module
Section 1 Introduction
1-3
Circuits internal to the module compare the frequencies of the
sound waves and extract the difference. An increase or decrease
in the frequency of the reflected wave indicates forward or
reverse flow. The degree of change is proportional to the velocity
of the flow stream.
1.1.4 Flow Rate Using measurements from the AV Sensor, the 2150EX can cal-
culate the flow rate. Many different flow rate conversion methods
are supported:
• Area Velocity
•Data Points
• Manning Formula
• Two-term Polynomial Equations
•Flumes
•Weirs
Often the 2150EX is chosen for applications where a primary
device is not available, nor is it practical to install a primary
device. Therefore, area velocity is usually the conversion method
of choice.
The 2150EX is capable of calculating and storing any two con-
version methods simultaneously. This feature is useful when it is
necessary to validate a flow conversion method. For example, the
flow rate at a new site programmed for area velocity conversion
can be directly compared to the flow rate calculated using a
Manning formula.
1.1.5 Total Flow The 2150EX can calculate and report the total flow. You can set
up the system to monitor net, positive, or negative total flow from
either of the calculated flow rates.
1.1.6 Data Storage Through Flowlink, you configure which type of data is logged and
the storage rate. For each measurement, the Data Storage Setup
window lets you turn the primary rate off, or select a rate from 15
seconds to once every 24 hours. If the primary rate is turned off,
the 2150EX will not store the measurement (unless a secondary
rate is selected). However, the 2150EX will still take readings if
that measurement type is necessary for a calculation.
Secondary rates are used to log data at a different rate when a
user-defined condition exists. For example, a secondary rate can
be used to increase the level and velocity data storage rate when
level is greater than or equal to a point of interest. Secondary
rates give you the best resolution of data, but only when it is
needed. Until the condition is met, the module will conserve
power and memory by storing the data at the primary storage
rate. Like the primary rate, you can turn the secondary rate off,
or select a storage rate of 15 seconds to every 24 hours.
Time Resolution The time resolution of each measurement is one second. That is,
readings are taken at the same time as the time stamp, not col-
lected and averaged over a period of time before the stamp.