Prole Programming
April 2019CXX-UM-03060-EN-01Page 28
Rotor Ratio
Figure 19: Ratio tab
The Rotor Ratio table provides a number of powerful diagnostic and analytical
features. In dual-rotor applications, the ratio of the upstream and downstream
rotors can be compared to provide self checks, diagnostic provision or
automatically determine the liquid viscosity.
Rotor ratio is typically configured at the factory; however it can be implemented
by the user as well. The flow processor obtain’s frequency data from each rotor
and calculates the frequency ratio. Once the flow processor calculates the ratio
it associates a high order polynomial and a Roshko number to the data. The
frequency ratio is calculated as follows:
RotorRatio =
Fb
Fa
Where, Fa = Frequency of Rotor A, and Fb = Frequency of rotor B.
Use this ratio function to address any potential failures in the meter. Because
the flow processor is comparing the frequency output of one rotor to the
other, you can determine if bearing failure, pickoff failure or even liquid
particulates are hindering meter performance. This same method is also used to
determine viscosity.
Figure 20: Load rotor table button
Upon editing any fields contained in the Rotor Ratio table, the Load Rotor Table
button appears in the menu bar as seen in Figure 20. This provides the ability to
write updated Rotor Ratio information to the EC80 Flow Processor.
OTE:N The Load Rotor Table button does not write the entire profile down to
the flow processor, it only writes the information contained in the Rotor
Ratio table.
Field Function
Error
Range
If the ratio is exceeded by the set percentage, the flow processor will output zero flow,
therefore stating a malfunction has occurred. Further prognosis could lead to pickoff failure,
bearing failure or flow processor failure
Error
Timer
Once the ratio is exceeded, therefore indicating a failure of some kind, the error timer
dictates how long the meter will have to stay in excess of the current set ratio percentage,
before an error condition occurs and zero flow results
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