Temperature-compensated quantitative dimensional measurement device with rapid temperature sensing and compensation

A self-temperature-compensated and workpiece-temperature-compensated dimensional measuring device comprising:

• a frame that exhibits a first predetermined dimensional sensitivity to temperature differences from a reference temperature;
• the frame comprising
• a "C" frame having two fixed shoes,
• dimensional measurement means movably referenced to the frame for measuring a dimension of a workpiece relative to the frame;
• wherein the dimensional measurement means serves as a moveable third shoe to the "C" frame,
• wherein the "C" frame and its shoes including the dimensional measuring means constitute in combination a three point snap gauge;
• first temperature measurement means in thermal communication with the frame for measuring a first temperature of the frame that is not equal to the first predetermined reference temperature;
• second temperature measurement means in thermal communication with the workpiece for measuring the second temperature of the workpiece;
• and
• computational means for receiving the measured workpiece dimension from the dimensional measurement means and the measured frame first temperature from the first temperature measurement means, and for calculating, in consideration of the first predetermined dimensional sensitivity of the frame to variations in temperature about a predetermined reference temperature, the temperature-normalized dimension that the workpiece would measure by the dimensional measurement means relative to the frame upon such times as the frame was at the predetermined, reference temperature even though the frame is at a first temperature not equal to the first predetermined reference temperature, and further for receiving the measured workpiece second temperature from the second temperature measurement means and for producing, in further consideration of a second predetermined dimensional sensitivity of the workpiece to variations in temperature about a predetermined reference temperature, that temperature-normalized dimension that the workpiece would measure by the dimensional measurement means relative to the frame upon such times as both the workpiece and the frame were at the predetermined, reference, temperature.

A workpiece-temperature-compensated and self-temperature-compensated measurement device comprising:

• a frame that exhibits a first predetermined dimensional sensitivity X.sub.Gauge to deviations from a first reference temperature T.sub.GStd, the frame comprising:
• a snap gauge frame exhibiting contact with the workpiece at at least three shoe points;
• an indicator of displacement referenced to the frame and displaced relative thereto by a workpiece for measuring relative to the frame a quantitative dimension of the workpiece G.sub.Wkpc, the workpiece exhibiting a second predetermined dimensional sensitivity X.sub.Wkpc to deviations from a second reference temperature T.sub.Std different from the first reference temperature T.sub.GStd ;
• first temperature measurement means in thermal contact with the frame for measuring a first temperature T.sub.GWkpc of the frame;
• second temperature measurement means, held by the frame in thermal contact with the workpiece, for measuring a second temperature T.sub.Wkpc of the workpiece;
• and
• computational means for receiving the measured workpiece dimension G.sub.Wkpc, the measured first temperature T.sub.GWkpc, and the measured second temperature T.sub.Wkpc and for calculating, in consideration of the first and the second predetermined dimensional sensitivities X.sub.Gauge and X.sub.Wkpc respectively of the frame and of the workpiece to deviations respectively from the first reference temperature T.sub.GStd and the second reference temperature T.sub.Std, the workpiece-temperature-compensated frame-temperature-compensated quantitative dimension G.sub.Wkpc +[(T.sub.Std -T.sub.Wkpc).times.X.sub.Wkpc ]-[(T.sub.GStd -T.sub.GWkpc).times.X.sub.Gauge ] that the workpiece would measure upon such times as both it and the frame were at the reference temperature.

An apparatus for the temperature-compensated dimensional measurement of a workpiece that is subject to a first predetermined dimensional variation with temperature deviation about a reference temperature, the measurement apparatus comprising:

• a gauge for producing at a first time a first signal representative of a dimension of a reference standard, and at a second time a second signal representative of a dimension of a workpiece wherein the gauge is in the configuration of a snap gauge for measuring an outside diameter of a workpiece;
• a first temperature sensor for producing at the first time a third signal representative of a temperature of the reference standard, and at the second time a fourth signal representative of the temperature of the workpiece;
• a computational means
• receiving at the first time the first signal from the gauge and the third signal from the first temperature sensor for computing, in consideration of a predetermined dimensional variation of the reference standard with variation in temperature about a reference temperature, a first temperature-compensated dimension that the reference standard would measure to the gauge should the reference standard be at the reference temperature even though the gauge is not, in fact, actually at the reference temperature,
• for using the first temperature-compensated dimension to calibrate the gauge, and
• receiving at the second time the second signal from the gauge and the fourth signal from the first temperature sensor for computing, in consideration of a predetermined dimensional variation of the workpiece with temperature about the reference temperature a calibrated workpiece-temperature-compensated dimension that the workpiece would measure to the gauge should the workpiece be at the reference temperature even though the workpiece is not, in fact, actually at the reference temperature.