Since your windmill gives out an AC voltage of 0 to 130V, you may use a small AC transformer to step it down. E.g. use a 120V to 6V transformer. Then use a diode bridge and some capacitor to rectify it into DC voltage. Now you can use two resistors to form a voltage divider and scale the voltage to the PLC's analog range (e.g. 0-5V on a T100M888+). The PLC will now be able to read the windmill output voltage while being isolated from it.
The same transformer output can also be connected to a single diode so that you get a half-wave rectification. You can then feed this half-wave to a transistor or ULN2003A and the output of the transistor can turn ON the PLC's digital input for half a cycle and OFF for another half cycle Now the PMON function could be able to measure the half wave frequency which is equal to half of the actual incomg pulse frequency.
If you use a F1616-BA you can connect the transformer AC output directly to the digital inputs 1-6 to measure up to 6 incoming pulses. No diode required since the F1616-BA can accept 24VAC inputs (Maximum of 50V p-p).
