I was playing around with one of these Hall effect magnetic field sensors when I noticed something I thought was strange. I held a cylindrical magnet several centimeters from the tip of the sensor and read the reading as around 5 mT. Upon reversing the magnet, the reading changed to around -8 mT (which is above its maximum rating). I was sure to keep the magnet a fixed distance from the sensor. The effect diminished greatly with distance, and the sensor appeared accurate at a range of around 10 cm.
I was curious as to why the sensor might produce different magnitudes dependent on the polarity of the magnet if the field is supposedly symmetrical. (Could it be that some part of the sensor is magnetized itself?)