Abstract: The dimensions of a countersunk hole, or of a fastener head, are determined accurately and rapidly by a nondestructive measurement system. At least one laser projects spots of light onto the surface being analyzed. From knowledge of the projection angle, and of the lateral displacement of the spots of light caused by variations in the depth of the surface, one can calculate an actual depth of each point on the surface. A set of parameters defining a mathematical model of the hole or fastener head are fitted to a set of measured coordinates of points on the surface being analyzed, using conventional numerical techniques. The optimized parameters define the dimensions of the countersunk hole or fastener head. The present invention operates independently of the coordinate system used to perform the measurements, so the invention eliminates errors caused by misalignment of optical components.

Abstract: A self-calibrating, remote programmable signal conditioning amplifier system employs information read from a memory attached to a measurement transducer for automatic calibration. The signal conditioning amplifier is self-calibrated on a continuous basis through use of a dual input path arrangement, with each path containing a multiplexer and a programmable amplifier. A digital signal processor controls operation of the system such that a transducer signal is applied to one of the input paths, while one or more calibration signals are applied to the second input path. Once the second path is calibrated, the digital signal processor switches the transducer signal to the second path, and then calibrates the first path. This process is continually repeated so that each path is calibrated on an essentially continuous basis. Dual output paths are also employed which are calibrated in the same manner.