A COMPUTER-INTERFACED FALLING BALL VISCOMETER

We have developed a system that greatly facilitates viscosity measurem ent under low-shear conditions, based upon a falling ball viscometer i nterfaced to a personal computer. Three optical sensors indicate the r ate of passage of a steel ball falling through a micro-capillary tube, and a potentiometer detects the angle of the tube. The resulting data are passed from a custom program with a graphical user interface to a spreadsheet. The spreadsheet then calculates and stores a value for t he viscosity of the sample, using the data passed to it from the visco meter, and a look-up table of stored slope and intercept values calcul ated from precision viscosity standards. We used the viscometer to det ermine the kinetics of actin polymerization, and to measure the viscos ity of F-actin-aldolase gels. This system provides significantly great er reproducibility and speed in data acquisition than does the traditi onal 'eyeball and stopwatch' method, and data reduction is virtually i nstantaneous.