Rockwell Automation 1756-CFM ControlLogix Configurable Flowmeter Module - Manual (Page 144)

144 Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
144 Frequency Accuracy
Use the following equation to calculate frequency accuracy in totalizer mode
for frequency period:
Speed
For speed, you must know the filter resolution. Use the following equation to
calculate frequency accuracy in totalizer mode for speed:
EXAMPLE
For example, in an application with the following
conditions:
 0.5s time period
 123Hz frequency
 25°C operating temperature
accuracy is determined with the following equation:
EXAMPLE
For example, in an application with the following
conditions:
 0.001 filter resolution
 25°C operating temperature
accuracy is determined with the following equation:
Accuracy =
(1) x (100)
(T
s
) x (F
in
)
Accuracy =
(1) x (100)
(0.5) x (123)
Accuracy = 1.626 + 0.005
+ 0.005%
Accuracy = +/- 1.631%
Value is added to
accuracy to account
for the crystal error
Accuracy = Resolution x 100
Accuracy = 0.1 + 0.005
Accuracy = (0.001 x 100) + 0.005
Accuracy = +/- 0.105%
Value is added to
accuracy to account
for the crystal error