You may or may not have heard, or perhaps are unfortunate enough to have experienced, the widely reported iPhone 5S bad compass and level readings where the calibration is widely off. According to sources, this issue could be due to a switch in suppliers for the accelerometer found in the iPhone 5S.
The conclusion is backed up by the fact the issue doesn’t appear to be apparent in the iPhone 5. The accelerometer for the iPhone 5 was supplied by STMicroelectronics, while the iPhone 5S’ part was revealed to be a Sensortech BMA220, which is made by Bosch.
The issue doesn’t appear to be a hardware fault, or a problem with the detection on the chip itself, but more with the calibration of it and what each accelerometer considers to be an acceptable zero-g offset.
Sources give some more granular detail about the calibration issue:
This is where we find the problem: the typical bias for the ST part is +/- 20mg, while the Bosch part lists +/-95mg. This almost 5x greater offset range is confirmed by our measurements, and is absolutely consistent with the failures being reported by users and the media.
iPhone 5S tolerance level
The issue can be easily fixed with a software update by Apple, but until then the miscalculation in the offset can be compensated and accounted for within apps by individual developers.
Whilst that is not an ideal solution and the ultimate fix would be a software update from Apple to resolve the differences in tolerance calculations, at least the issue can be compensated for. The good news is that it doesn’t appear to be a hardware fault, which was originally suspected.
So until the developers begin correcting the measurements themselves, or Apple issue an update, just make sure you carry an old fashion compass and level with you. Just kidding…