Xylem XL Series H-522 - Plus - Manual (Page 116)

13-6 Counter And Frequency Inputs
XL™ Series
This option allows the user to enter an offset into the frequency calculation.
NOTE: The offset is only applied if the input frequency is not 0.0. The frequency input is
normally used for wind speed sensors, and the offset value is a low number that represents the
drag of the sensor. If there is no wind, meaning the raw frequency input is 0.0, the reported value
should be 0.0 and not the offset. Therefore the offset is not applied when the wind is not blowing.