Abstract: Improved calibration standard construction for X-ray fluorescence thickness measurement gauges formed of one or more plated layers of known character and thickness disposed on an apertured supporting foil base and accessible to X-radiation through an aperture at the base of a conically shaped bore in a surrounding protective housing member.

Abstract: A probe guide for holding a coating thickness measurement probe in contact with a coated workpiece such that repeatable thickness measurements may be made without the necessity of the user manually positioning the probe head for proper contact. The probe guide having a probe holding assembly mounted on a stand; the probe holding assembly constructed to permit the probe to swivel freely in any direction about the geometric center of the probe head face. A workpiece holding means is provided for holding the workpiece against a probe head of the probe. By positioning the workpiece holding means to forceably move the workpiece into contact with the probe head face, the probe will swivel until the resultant vector through the center of moment of the static forces through the workpiece acting on the probe head at the point or points of contact between the workpiece surface and the face of the probe head passes through the geometric center of the probe head face.

Abstract: An improved probe assembly for measuring the conductivity of a plated through hole in a circuit board. The probe assembly having a longitudinal housing and including at the forward end thereof a segmented current injection electrode, each segment being spring biased forwardly and capable of independent movement longitudinally with respect to the housing between a forward position and rearward position. The segmented current injection electrode injecting current into the through hole substantially 360.degree. of the circular edge formed by the intersection of the walls defining the through hole and the surface of the circuit board. A voltage measurement electrode being a knife-blade electrode is positioned in the interstices between the segments of the current injection electrode. The voltage measurement electrode also being spring biased in a forward direction and capable of longitudinal movement between a forward position and a rearward position.