A metrology tool is arranged to measure a parameter of a substrate that has been provided with a pattern in a lithographic apparatus. The metrology tool includes a base frame, a substrate table, a sensor, a displacement system, a balance mass, and a bearing. The substrate table is constructed and arranged to hold the substrate. The sensor is constructed and arranged to measure a parameter of the substrate. The displacement system is configured to displace the substrate table or the sensor with respect to the other in a first direction. The bearing is configured to movably support the first balance mass so as to be substantially free to translate in a direction opposite of the first direction in order to counteract a displacement of the substrate table or sensor in the first direction.