A simple electronic capillary microviscometer.

Inexpensive electronic components were adapted to a miniaturized version of a falling-ball viscometer. This allowed automatic determination of relative viscosities of Newtonian fluids with 1% accuracy and employing only 10 to 30 microliters of sample or about 1 microgram of some biological materials. The electronic microviscometer was tested with bidistilled water at several temperatures, with CS2SO4 and glycerol solutions, several organic liquids, and some preparations of high-molecular-weight hyaluronic acid. Details of construction, circuitry, temperature control, operating procedure, and calculations are given as well as an evaluation of the instrument's performance in terms of previously established criteria.