Inaccurate LV-MaxSonar-EZ4 Ultrasonic Sensor

So, first time using ultrasonic sensors in general, and on first attempt with this sensor, it's clearly not calibrated properly at all. It's consistently giving out values of 56-57inches, which is very strange because nothing is at 56-57 inches from where the sensor is. It's laying flat on the table, with nothing around but the ceiling above it (75inches from the sensor). So, how to fix this?

Furthermore, the sensor is getting the increments completely wrong. I'll move 5 inches before it goes down from 57 to 56 inches. Is this something wrong with the sensor itself or ...?

Note: I'm using the PW pin on the sensor board. Not its Analog pin.

Update: Now it's just giving out values of 0.

Update: And now, it's going nuts with noise, giving out random values between 30-60 and occasionally 0 with nothing changing in its environment.

Update: Ok, so I've modified my code to take in 50 values and average them out. And now there is at least some precision. What the Arduino reads go as follows: if my hand is (over the sensor) within 2-4in of the sensor, the Arduino reads a value of 56inches. If it's anything beyond that (I put my hand higher or just not place it over it at all), the value reads 57inches. SO basically, it became binary...

Do you have a link to the datasheet of the sensor as I am not familiar with it.

robtillaart:
Do you have a link to the datasheet of the sensor as I am not familiar with it.

There you go.