Rockwell Automation 1756-CFM ControlLogix Configurable Flowmeter Module - Manual (Page 145)

145 Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
Frequency Accuracy 145
Frequency Average
For frequency average, you must know:
 Application frequency (F
in
)
 Number of accumulated in sample time (Counts)
Use the following equation to calculate frequency accuracy in totalizer mode
for frequency period:
EXAMPLE
For example, in an application with the following
conditions:
 25 meter samples
 123Hz frequency
 60°C operating temperature
accuracy is determined with the following equation:
Accuracy =
(1) x (100)
(0.02) x ( Number of meter samples) x (F
in
)
Accuracy =
(1) x (100)
(0.02) x (25) x (123)
Accuracy = 1.626 + 0.01
Accuracy = +/- 1.636%
+ 0.01
Value is added to
accuracy to account for
the crystal error over
the temperature range