The present versions of LIFA or LINX do not provide the capability to measure frequency or period. This means the present versions of LIFA or LINX can not be used with sensors that produce a variable frequency output proportional to flow rate. Your options are modify liFA or LINX to add frequency measurement capability, Or use the serial write read capability of Labview and the Arduino code available on the Internet to capture the flow meter data. This second option does not use LIFA or LINX. A third option is use a frequency to voltage converter to convert the variable frequency output of the flow meter to a voltage and the analog read capability of LIFA or LINX.
Here is an example of a frequency to voltage converter.
<http://www.ti.com/lit/ds/symlink/lm2907-n.pdf>
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