What kind of sensor I have to huse?

[system]

I bought A1302 EUA hall sensor. I have attached the datasheet.
I tried to connect it on arduino as in the scheme attached, and with this code:

const int hallPin= 4;

void setup() {
  Serial.begin(9600);
  pinMode(4, INPUT);
}

void loop() {
  int sensorValue = digitalRead(4);
  Serial.println (sensorValue);
}

but with the serial monitor I have alway 0. why?

datasheet A1302 EUA.PDF (293 KB)