The AS5048 is insensitive to external magnetic stray fields as many other magnetic rotary encoder devices from ams OSRAM are. The solution is that the differential voltage is measured between the Hall elements during sampling. This gives a positive and negative voltage on the Hall-elements – Vdiff1. If the external magnetic stray field comes in, the voltage drops on one Hall element and increases at the same time with the same value on the other Hall element. That means the differential voltage is still the same. This explains why Vdiff1 is equal to Vdiff2 after an external magnetic stray field comes in.