Reading a MPX4250AP for beer carbonation control.

Other Hardware Sensors
1

Hi.

I'm using an arduino mega 2560 and a http://www.freescale.com/files/sensors/doc/data_sheet/MPX4250A.pdf to read the pressure in a brite tank. This is to control the carbonation volume of beer. Because beer carbonation is a relation among pressure and temperature.

I'm not sure if i'm getting readings correctly. Voltmeter read is about 1.5volts. I'm using the recommended circuit just I haven't used 105 ceramic capacitor because i didn't find one. I used 104 cap.

This is my test code.

int sensorPin = A0;   
float sensorValue = 0;  

void setup() {
  Serial.begin(9600);
}

void loop() {
  sensorValue = analogRead(sensorPin);    
  float x;
  
  x=(((sensorValue/1023)+0.04)/0.004) * 0.145; //by 0.145 to calc psi 
  Serial.println(sensorValue); 
 
  Serial.println((float)(x),4);
  delay(1000);  
}

I'm using float for accuracy.

My reasoning is as follows...
This reading at my place, open to the atmosphere is 12.18psi. It is supposed to be 14.5 psi at sea level. Here i'm at 1500 above sea level. So 2.32 psi difference corresponds to my altitude, latitude, weather, etc. right? If i hook it up to the tank I'll be reading correctly the pressure? I need to use a correction factor to compensate the reading? or I need a different sensor for my needs.

Regards.