Solenoid valves have been used for more than 100 years in many diverse flow control applications across many industries. But their underlying technology has not changed a great deal until recently. Even so, the physics of their operation is not always well understood, leading to misapplications or suboptimal performance. For example, not all users realize that simple solenoid coil excitation with AC rather than DC power usually allows for higher forces, watt-for-watt, in opening a poppet valve. So AC may be helpful against higher differential pressures of the fluid, for instance. However, using DC power often provides other advantages, such as ease of wiring.