Mace HVFlo XCi, Руководство по эксплуатации продукта

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To overcome this problem, MACE XCi devices include the maximum measurement count feature whereby if
the instrument detects a state change (i.e flow has started or flow has stopped) it stays on and takes X
number of readings to confirm this situation. If all X number of readings meet the criteria for a valid reading
as set by, peak threshold, flow threshold, minimum stream activity and stream activity percentage, then the
reading is accepted and the change of state confirmed. If the readings do not all agree that there has been a
change of state, then the reading is “discarded” and the current flow state remains. That is, the unit continues
to calculate zero flow or accepts the flow rate as calculated. Furthermore, the instrument also checks that the
direction of flow has not changed within the X readings. For example, if there is zero flow and the unit detects
a reading of positive flow and another of negative flow then the overall reading is discarded and the unit
continues to register a zero flow.
The number of readings used for the maximum measurement count is configurable by the user.
Calculation method
“Pump method”
Under normal conditions, water flow that is provided by a
pump is turbulent and contains a vast number of
acoustically reflective particles, particularly miniature air
bubbles that are a result of cavitation events. In monitoring sites that are pumped, or where low signal
strengths are uncommon, the pump method should be used.
"Surface wave rejection”
In severely turbulent, open conduit flows
such as encountered in a sewerage system,
it is common for standing waves to develop
in the flow stream. If situated closely, these
standing waves (surface waves) may
confound a Doppler ultrasonic sensor because they typically result in reflections of a significantly slower
velocity. In the diagram, a surface wave can be seen as a sharp peak on the real-time graph at about the 0.2
m/s mark.
In this case, if the user selects the surface wave rejection calculation method a menu item called “low-end
cutoff” will be displayed. This feature enables the user to force the instrument to ignore Doppler shifts that lie
between zero and the low-end cutoff. The low-end cutoff is a percentage of the range (x-axis) of the real-time
graph. In the diagram the low-end cutoff would be configured to about 10% of the graph. That is, any data
that are received between 0 and 0.4m/s will be ignored when computing an average stream velocity
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