Hawk Measurement, Middleton, MA, offers rotation switches that use a rotating vane to detect the level of a dust or powdered material. A brushless synchronous motor turns the vane slowly; as long as the powder level remains below the vane, the vane can turn freely. If the powder rises to the vane's level, the rotation stops, the motor turns off, and an output for an external control system is produced. The switch can be used for powdered materials with low densities (>100 g/l or 6 lb./ft.3) and carries ATEX and FM approvals. Applications include plastics, building materials, food processing, pulp and paper, chemical processing, and metal production.