30 Years of Progress in Viscometers and Rheometers
Abstract The history of commercial viscometry and rheometry over the last thirty years is summarised. In terms of those instruments that have established themselves in a lasting position in the field, we highlight the importance of a sound original idea, good marketing, and constant improvement as technology advances. Instruments in this area fall into three categories: simple, low-cost instruments to measure viscosity or at least an equivalent Newtonian viscosity; multi-speed instruments often able to record data on another display or storage device, and rheometers, i.e. instruments capable of a rotational shearing action, as well as one of the following: oscillation, creep and normal force measurement to give some measure of viscoelasticity. The advances in technology in many areas over the past 30 years have all fuelled the rapid development of instruments that has been nothing short of astonishing. Of especial importance has been the continuous developments of electric motors, and transducers, as well as the increases in speed and memory and reductions in price of digital processors and microprocessors. With this increased computing power perhaps with instruments using complex flow regimes it may be as easy to analyse data as with simple shearing now. There will always be, however, those who want to go to higher frequencies, lower deformations, etc., to meet those challenges of measuring the rheology of materials at the limits.