How can I measure percentage of pulse signal

I am working on a project. I need get pwm signal on raspberry pi then find the open interval which means percentage of the signal. I design a system but it does not work properly.

I can reach the correct value without delay but when I decrease the percentage it keeps max value.

Answer 1

[Ryan Takatsuka]

You are probably better off filtering the PWM signal to find the interval percentage. See the attached example.

[Dogukan Arat]

It works thank you but my period will be 20ms. When I change the period of the pwm, it does not work. How can adjust the filter for this period?

[Ryan Takatsuka]

If you have the Signal Processing Toolbox, you can use the filterDesigner app to design a lowpass IIR filter. Otherwise, there are some online tools such as this one: Online Filter Designer

 I've attached an example of a filter using a 0.020 s period with an arbitrary sampling rate.