The simple concept outlined in “Capillary Flow Porometry” requires careful, logical experimental implementation. Parameters such as speed, range, and non-equilibrium behavior must be considered. Besides “Pressure Scan” employed in the POROLUX™ 100 and POROLUX™ 500, there is another – more sophisticated – approach called “Step Stability”. This method is employed by the POROLUX™ 1000 instruments.
At the heart of the pressure step/stability method is precise, repeatable, device independent pressure step control. This is achieved by a unique, complex system which consists of a pressure regulator working in tandem with a precise, computer controlled, flow-control valve. This valve can be positioned with fine resolution to fine-tune specific target pressures (note that pressure control in a sealed system is trivial, but in a complex implementation such as this – with a changing back-pressure – simple controls are insufficient).
Specific pressures are targeted, and achieved with minimum delay (to avoid certain experimental errors) and data points recorded only after user- defined stability criteria have been met (for both pressure and flow). In this way, the POROLUX™ 1000 records only data at equilibrium – pores which take longer to open, due to factors like tortuosity, sample thickness/length or even viscosity, will accurately be accounted, thus achieving the most realistic representation of pore size from a material. The Porometer team has uniquely tested and comprehended these complex phenomenon so that we may offer the most meaningful methods and instruments on the market – please contact us for further details.