you don't want to put 9v directly on the pin
This means don't connect 9 volts to any arduino digital or analog input pinthe maximum is 5 volts for a board that is running on 5 volts!
The maximum voltage you should connect to these pins is the voltage powering the controller chip (usually 5 volts)If you want to measure 9v you would use a voltage divider.
The method called a voltage divider is used to measure more than 5 voltsThe value you read will always be 5v divided by 1024 but if using a divider ( say with two equal value resistors to divide the voltage in half) 1024 would equal 10 volts.
If you use a voltage divider to divide the voltage in half (using two equal value resistors) then the maximum value from analogRead will actually be 10 volts ( you get 5 volts on the pin because you have given 10 volts into the voltage divider and that has divided the voltage in half)
thanx mate understood... except 4 the first part...
you don't want to put 9v directly on the pin
i got a 9V pin i audrino board so i can take a 9v output rite??