Sorry for the late answer I had some stuff to do.
Okay so, the circuit is connected like this:
Voltage: V+ which is the 5V DC connected to SW5
Ground: Ground to Ground
Analog = PO or PH analog output is connected to the Analog pin A0
I used three resistors to test which one will be close to the voltage required, I will post a picture of the three of them.
The voltage output I get from your code displays more than 5V, I can’t calibrate it to 2.5V that way.
The circuit is guarantee is properly connected.
Also you have been helping me out a lot, I appreciate it.