In spite of the simplicity of such a layout, the experiments are not easy. The magnetization can be measured accurately with the help of a pickup coil around the cylinder, but the associated change in the angular momentum is small. Furthermore, the ambient magnetic fields, such as the Earth field, can provide a 10 –10 times larger mechanical impact on the magnetized cylinder. The later accurate experiments were done in a specially constructed demagnetized environment with active compensation of the ambient fields. The measurement methods typically use the properties of the torsion pendulum, providing periodic current to the magnetization coil at frequencies close to the pendulum's resonance. The experiments measure directly the ratio: λ λ = Δ Δ J / Δ Δ M and derive the dimensionless gyromagnetic factor g ′ of the material from the definition: g ′ ≡ ≡ 2 m e 1 λ λ . The quantity γ γ ≡ ≡ 1 λ λ ≡ ≡ e 2 m g ′ is called gyromagnetic ratio.