Abstract

When measuring the mass and the coordinates of the centre of gravity of a large structure, reliability, reproducibility and measurement accuracy are increasingly important. The various items that affect the measurement accuracy will be discussed. A method is given for the determination of an overall uncertainty, starting from errors that cannot be eliminated by proper corrections, in combination with the statistical uncertainty of the proper corrections, in combination with the statistical uncertainty of the measurements.

A standardized weighing procedure is described, underlining stable and reproducible loading conditions to get good statistical reliability.

The state of the art in the best attainable measurement uncertainty is given.

Introduction

When weighing large structures for either onshore or offshore use, the intention is to determine the mass and the location of the centre of gravity. No matter whether the weighing is for either financial purposes or that the results are needed for safety during transport or in active operation, reliable and accurate measurements are of increasing importance.

With a view to the importance of the results of the weighing, high demands are made - and rightly so - upon the measurement accuracy and the reproducibility. Load cells based on resistance strain gauges are nowadays of such high quality and reliability that the overall accuracy of the weighing is only partly determined by the properties and specifications of the load cells and the indicating instrument.

The authority carrying out the weighing should do so according to a well-reflected and defined method. They must be able to issue a document which describes the weighing procedure in detail and in addition a second document that defines the accuracy and the total measurement uncertainty, including its calculation procedure.

Prior to a more detailed discussion of error summation, it is already Prior to a more detailed discussion of error summation, it is already emphasized here that in the error summation procedure not only the precision of the load cell is involved but also and in particular the precision of the load cell is involved but also and in particular the measurement uncertainty of the weighing.

In this paper full attention will be paid to this, whilst the possible inaccuracies will be distinguished as far as type and origin are concerned.

p. 9–91 p. 9–91

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