Apparently you do not understand me.
If you want to convert the measured humidity value in Hz into an output voltage signal (0-10V), you also need to know what the measured frequency is.
Example:
825 Hz = 0% humidity = 0 V output signal, 1100 Hz = 1.64 V output signal, 2500 Hz = 100% = 10 V output signal.
If you use the values from your first post:
500 Hz = 0% humidity = 0 V output signal, 1100 Hz = 3.00 V output signal, 2500 Hz = 100% = 10 V output signal.

That's why you have to know what the measured frequency means.
I asked you to tell me who the manufacturer of the sensor is and what type (or order number) it is.
If you expect help, please also give answers to questions asked.

Hello #dP,

I'm also aware that the TS does not know the scale of the sensor.
But have you ever experienced that the manufacturer does not tell you the specification?
That's why I asked him to tell me the manufacturer and the type of sensor.
That the LOGO! is not an arithmeticist, should be well known, moreover, she does not handle floating point arithmetic. In some cases, when converting a formula, you have to calculate intermediate results with a pocket calculator and use this value so that the error deviation does not become too large.
And since the measured frequency is to be converted into a voltage signal 0-10V, so you must know what the frequency range of the output signal of the sensor is.

1100 Hz with hands on the sensor say me nothing.