CALIBRATION AND ERROR ANALYSIS OF A NEW MAGNETIC SPHERE MICRORHEOMETER

A magnetic microrheometer has been built, which can be used to study t he rheological properties of materials that are available in small vol umes and have distinct phases. The instrument performs creep tests (di splacement in response to an imposed force), using magnetic microspher es of diameter 7 mum and larger. Displacement histories of the spheres are video-recorded and analyzed, with high resolution, using computer vision methods. In this article, results are presented for the magnet ic force calibration and for a test using a Newtonian fluid to evaluat e the performance of the instrument. A comprehensive analysis of the d ifferent sources of error in measuring Newtonian fluid viscosities was performed, resulting in quantitative delineation of the accuracy and precision of the microrheometer.