Flow sensor, fluctuating analogRead values

Hello,

I try to connect a flow sensor (Honeywell AWM720P1) to my arduino, but the analogRead receives weird data. It is fluctuating from 0 to 500. It is connected to a 12v external power supply.

Whats wrong???

Regards,

Bram

datasheet : http://sensing.honeywell.com/index.php/ci_id/50061/1a_id/1/document/1/re_id/0

int flowPin = A0;
//int flowVoltage = 0;

float flowValue;

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

void loop () {
  int flowVoltage = analogRead(flowPin);
  flowValue = flowVoltage* 0.0049;
  Serial.print(flowVoltage);
  Serial.print(",");
  Serial.println(flowValue);
  delay(500);
}

Is the sensor ground (-) connected to Arduino ground?. The data has the look of a floating input.

Thank you!! it works now