A method is proposed to determine the effective detector area for energy-dispersive X-ray spectrometers (EDS). Nowadays, detectors are available for a wide range of nominal areas ranging from 10 up to 150 mm2. However, it remains in most cases unknown whether this nominal area coincides with the “net active sensor area” that should be given according to the related standard ISO 15632, or with any other area of the detector device. Moreover, the specific geometry of EDS installation may further reduce a given detector area. The proposed method can be applied to most scanning electron microscope/EDS configurations. The basic idea consists in a comparison of the measured count rate with the count rate resulting from known X-ray yields of copper, titanium, or silicon. The method was successfully tested on three detectors with known effective area and applied further to seven spectrometers from different manufacturers. In most cases the method gave an effective area smaller than the area given in the detector description.

The behaviour of piston-cylinder operated pressure balances is characterized by thedistortion coefficient λ and zero-pressure effective areaA0 which model the variation of a pressure balance’s area interms of the applied pressure. This paper determines the uncertainties inλ and A0 when utilizing the method ofcross-floating with another pressure balance standard whose parameters and associateduncertainties are known. A limitation that is frequently encountered in many attempts ofthe uncertainty analysis for a pressure balance is that no readily accessible uncertaintyquantification framework for the distortion coefficient is present. As a result theuncertainty in a pressure balance’s area at elevated applied pressures is typicallyunderestimated in the absence of this uncertainty information. We firstly review theuncertainty formulation for a pressure balance generated pressure involving correlationeffects in terms of an implicit multivariate matrix equation approach and then utilizingthe resulting solution present the methodology to consistently perform the uncertaintyanalysis for λ and A0.

A common measurement model for a gas operated piston-cylinder based pressure standardeffective area is the well known integral equation formulation originally developed byDadson of the NPL. However a problem with directly applying this exact mathematical modelis that it cannot be easily cast into a functional form suitable for application of theGuide to the expression of Uncertainty in Measurement (GUM) which is reliant on theconcept of sensitivity coefficients without various simplifications. In this paper, weexamine the standard approximations that are currently necessary in order to directlyapply the GUM for a pressure standard effective area uncertainty determination. We alsocompare and contrast this to the exact effective area uncertainty results obtained throughthe direct application of the Monte Carlo Method (MCM) which has recently been publishedas Supplement 1 to the GUM. Based on these investigations we also draw some preliminaryconclusions on the relative merits on the extent to which the shape of the piston andcylinder radii and whose uncertainties may vary along the engagement length of thepiston-cylinder may be modeled and incorporated into a piston-cylinder’s effective areauncertainty calculation.