How to connect a varying output voltage to the Arduino?
If “what I want is counting the pulses of my meter” means that you want to count the number of pulses the meter produces, you can use a circuit like the following to clip the voltage into the 0-to-5V range (as acceptable for inputs on Uno digital pins).







simulate this circuit &ndash; Schematic created using CircuitLab

Then, to count pulses, write a sketch that repeatedly reads the selected input pin.  Each time it changes from low to high, add one to your count of pulses.

If you don't have 5.1V zener diode like the 1N4733A, you could instead attach the anode of an ordinary diode to the junction of R1,R2 and its cathode (the cross-bar end) to 3.3V on the Uno.  This will clamp the voltage on the input pin to at most about 4V.  (Note, with such a diode clamp, there would be high-current problems if you subsequently changed the pin to a high output.  You could of course put a 100Ω resistor in series with the clamp diode if you are concerned about that.)