Measuring relative concentricity deviations in a confined space between two circumferential elements

A tool for measuring relative concentricity deviations in a confined space between a turbine rotor and a turbine diaphragm, the tool comprising:

• a housing;
• a sensor coupled with the housing, the sensor measuring a distance from the housing to one of the turbine rotor and the turbine diaphragm;
• an axial spring plunger connected to the housing;
• a radial spring plunger connected to the housing and orthogonal to the axial spring plunger;
• and
• a sliding or rolling surface on a side of the housing opposite from one of the axial spring plunger and the radial spring plunger,
• wherein the housing is sized to fit in an L-shaped groove formed in the turbine diaphragm, and wherein the housing comprises an axial step section protruding axially from the housing and extends substantially to a floor of the groove such that the housing is shaped corresponding to the L-shaped groove in the turbine diaphragm.