Classical Calibration Methods Research Articles

Densimeter calibration method versus temperature and pressure

This article reports a calibration procedure for the commercial Anton Paar DMA 512 densimeter usable at pressures up to 40 MPa. The method is based on water as a reference substance and requires knowledge of the characteristics of the cell as functions of temperature when subjected to a vacuum lower than 100 Pa. Comparis on with data from the literature indicates a relative accuracy of 0.1% where the classical calibration method (i.e. assuming no dependence of the densimeter performance upon pressure) led to a relative accuracy of 0.8% for the same substances.

Interval estimation in calibration models : an application of fieller' theorem

In this note we demonstrate how Fieller' theorem may be used to provide interval estimates for calibrated data obtained using the classical calibration method. Using a matrix formulation of teh general linear model, it is sraightforward to incorporate extensions to the univariate, multiple regression setting. The results provided are easily programmed in a matrix-based language such as GAUSS.

Moisture gauge calibration based on the distribution of neutrons scattering in construction materials

The counting rate, measured by a counter with BF 3, for slow neutrons scattering in material containing water, is presented under three terms. The counting rate given by the theory of neutron transport in water [4] is used as the first term; the counting rate obtained on dry and homogeneous test material is used as the second, and the apparatus background counting rate as the third term. The average distance between source and counter is established by means of a nomogram (fig. 1) in terms of moisture. The influence correction of the drill hole diameter is realized by multiplying the counting rate by a cavity factor obtained from the ratio between the counting rates for a certain cavity and those for the reference cavity. By utilizing the proposed method of measuring the above-mentioned three counting rates and the counting rate of a test material with known moisture, the radiometric moisture gauge can be easily calibrated without using the classical calibration method, which is very difficult to apply for a great number of points in the entire moisture measuring range. The proposed method is checked by comparing the calculated calibration curve with the experimental curve for two average distances between source and counter, and for different materials like: soil, sand, aggregates and cement concretes.