Hi Peter - the operating range is roughly 160-180 degrees. You need to keep the neodymium magnets as close to the sensor as possible in order to get the best result.
g.
Printable View
FWIW, this method offers 10-bit resolution.
The Teensy 3.0 offers either 13 or 16 bit resolution, I'm not completely sure which, on its fourteen analogue inputs, for $27. And it can be configured to act as a joystick.
Teensy 3.0 + header ID: 1044 - $27.95 : Adafruit Industries, Unique & fun DIY electronics and kits
(I have no commercial interest in any of the manufacturers or retailers of Teensy!)