Measurement of liquid film thickness by optical fluorescence and its application to an oscillating piston positive displacement flowmeter

The movement of the circular piston in an oscillating piston positive displacement flowmeter is important in understanding the operation of the flowmeter, and the leakage of liquid past the piston plays a key role in the performance of the meter. The clearances between the piston and the chamber are small, typically less than 60 νm. In order to measure this film thickness a fluorescent dye was added to the water passing through the meter, which was illuminated with UV light. Visible light images were captured with a digital camera and analysed to give a measure of the film thickness with an uncertainty of less than 7%. It is known that this method lacks precision unless careful calibration is undertaken. Methods to achieve this are discussed in the paper. The grey level values for a range of film thicknesses were calibrated in situ with six dye concentrations to select the most appropriate one for the range of liquid film thickness. Data obtained for the oscillating piston flowmeter demonstrate the value of the fluorescence technique. The method is useful, inexpensive and straightforward and can be extended to other applications where measurement of liquid film thickness is required. © 2011 IOP Publishing Ltd.

Calculation and measurement of the magnetostriction of multilayered composites

A new theoretical model that predicts the magnetostriction of multilayered composites has been developed. The model takes into account the shear stress between the composite layers and consequently predicts a non-uniform strain along their thickness. The model has been experimentally validated by producing composites formed from three materials with different magnetostrains and mechanical properties, and controlled layer thicknesses in the order of micrometers. Deformations of several ppm, up to 7.5% of the saturation magnetostrain were measured between the edge and the centre of such composites. © 2006 Elsevier B.V. All rights reserved.