1. A magnetic field sensor, comprising: first and second magnetic field sensing elements having respective first and second maximum response axes, the first and second maximum response axes pointing along respective first and second different coordinate axes, wherein, in response to a magnetic field, the first and second magnetic field sensing elements are operable to generate first and second magnetic field signals; and an electronic circuit coupled to receive the first and the second magnetic field signals, wherein the electronic circuit is configured to: determine a magnitude of a vector sum of the first and the second magnetic field signals; and provide one or more signals in response to the magnitude of the vector sum determined, wherein the electronic circuit configured to provide one or more signals in response to the magnitude of the vector sum determined comprises an electronic circuit configured to provide a warning signal if the vector sum of the magnetic field exceeds a threshold value, and wherein the threshold varies as a function of a phase of the vector sum.