Optical assembly with adjustable optical element and independently tunable position sensors

A device assembly (16) for a precision apparatus (10) includes a device housing (30), a device (32), a device mover assembly (34), and a measurement system (36). The device mover assembly (34) moves the device (32) relative to the device housing (30) about a first axis and about a second axis that is orthogonal to the first axis. The measurement system (36) monitors movement of the device (32). The measurement system (36) monitors movement of the device (32) and can include a first sensor assembly (260) that monitors movement about the first axis and a second sensor assembly (262) that monitors movement about a second axis. Each sensor assembly (260) (262) can include a sensor adjuster (474) (476) that adjusts the position of a portion of the respective sensor assembly (260) (262) to independently tune the sensor assemblies (260) (262) and independently enhance the performance of each sensor assembly (260) (262). Further, each sensor assembly (260) (262) can be a magnetic type sensor.