An additive manufacturing machine includes an energy beam system situated in a fixed position relative to a reference plane coinciding with an expected location of a build plane, an energy beam system with an irradiation device configured to generate an energy beam and to direct the energy beam upon the build plane, and a position measurement system configured to determine a position of the build plane. A position measurement assembly includes one or more position sensors, and one or more mounting brackets configured to attach the one or more position sensors to an energy beam system of an additive manufacturing machine. The position measurement assembly is configured to determine a position of a build plane with the energy beam system situated in a fixed position relative to a reference plane coinciding with an expected location of the build plane.