MULTILAYER EXCITATION RING

The disclosure describes a magnetic circuit assembly that includes a magnet assembly and an excitation ring. The magnet assembly defines a central axis and includes a pole piece and a magnet underlying the pole piece. The excitation ring includes a base and an outer ring positioned around the magnet assembly. The base includes a platform layer underlying the magnet, an upper base layer underlying the platform layer, and a lower base layer underlying the upper base layer. The outer ring overlies the upper base layer and is configured to couple to an outer radial portion of a proof mass assembly. The platform layer and lower base layer are made from high coefficient of thermal expansion (CTE) materials, while the upper base layer and outer ring are made from low CTE materials. Each relatively high CTE material has a higher CTE than each relatively low CTE material.