Arduino + Pressure Sensor

Help! I am planning to interface a pressure sensor to arduino http://philippines.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0286686

This sensor uses difference of two pressures. Pressure range is 0-5psi. The supply of this sensor is 10-16V and the output is 1.5mV-50mV. 10mV for every 1psi increase.

I already have an amplification circuit which makes the output goes up to 0-7.5V which is then fed to a voltage divider so the maximum output now is 5V which is compatible to the analog input pins of the arduino.

I am confused as to what will be the value of my AREF (Analog Reference) for the ADC...

The default is 5V (or whatever the 5V rail is at - often less when USB powered) or you can force it to use 1.1V or you can feed your own voltage (up to 5V) onto the AREF pin to use as a base.

http://arduino.cc/en/Reference/AnalogReference