First, let’s examine the operation of a simplified normally closed poppet valve (Figure 1). When the coil is not energized, no electromagnetic forces are generated; the conical spring (f) presses the disk (a) with its attached core (c) against the orifice (b), stopping flow. The disk is typically made from an elastomeric material to ensure a tight closure. When electrical current is passed through the coil (d), a magnetic field (h) is induced in the magnetically permeable circuit, comprised of the stationary plugnut (e), movable core (c), and yoke (j). The resulting electromagnetic force attempts to close the air gap (g) by moving the core towards the plugnut. When the core lifts, compressing the spring, the disk moves away from the orifice and flow commences. A larger orifice selection allows a greater flow coefficient (or Cv) — the amount of flow for a given pressure drop