This paper is part of the special publication Developments in petrophysics (eds M.A. Lovell and P.K. Harvey). A steady-state probe permeameter is designed that is robust, insensitive to moisture and can be operated using a low-pressure gas source. Consequently, substantial reduction in weight and bulk are possible and a truly one-man-operable, lightweight (<5 kg) instrument is constructed. Tests on natural samples using a prototype instrument reveal a similar level of precision to other permeameters over a wide range of permeability.