The invention concerns a clamping piece having a fixing end which can be fixed to a structural profile member or the like and a clamping end having two clamping limbs which enclose a clamping eye and which can be tightened by way of a tightening means. The method includes the steps of placing reactants in a microwave-transparent vessel, placing the vessel and its contents into a microwave cavity, applying microwave radiation within the cavity and to the vessel and its contents while concurrently externally cooling the vessel conductively. Such sensor measurements may be weighted according to a decreasing function of uncertainty associated with sensor values. Various embodiments are disclosed. The magnetic field sensitivity of the first and second three-dimensional magnetic sensors may be less than the magnetic field sensitivity of the one-dimensional magnetic sensors.