What is your ADC reading at 0 pressure? Should be near 104.
See if this helps out, change "adcMin" to whatever your 0 pressure ADC value is.
int adcMin = 104, // ADC reading @ 0 pressure
adcMax = 921; // " " " 12 Bar
float pressure,
pressureMax = 12.0;
void setup()
{
Serial.begin(9600);
}
void loop()
{
pressure = (analogRead(A0) - adcMin) / float((adcMax - adcMin)) * pressureMax;
Serial.println(pressure);
delay (1000);
}
If you still have problem with "jitter" you might try a 100nF ceramic capacitor from pin A0 to GND, or you may need a "smoothing" routine in your code.