A piston assembly includes a housing, a piston (106) positioned within the valve housing (102), and an inductive proximity probe sensor (104) positioned on the housing configured to detect a position of the piston with the housing. The piston is configured to at least one of rotate or translate axially relative to the housing. The piston includes a variable surface (108). A fuel control system includes the piston assembly (100), a servo valve (116) in fluid communication with the piston assembly, and an engine controller (114). The engine controller is operatively connected to the inductive proximity probe sensor.