The strength of a magnetic field can be measured as strength in a specific direction.
We can calculate the strength of a magnetic field along the field lines from measuring the strength in x,y,z direction separately and calculating it from this.
Is it possible to measure the same with a single sensor, instead of three?
Can a 3D compass needle measure the the force along its orientation, for example?
I am curious not only about existing sensors, but also about ones that could work in principle only, and can not practically be build.