Obtaining representative samples with minimised sampling errors, is critical for calculating accurate metal-lurgical mineral balances on process plants. A challenging situation exists, where no acceptable, robust or economically viable sampler has been commercialised for sampling of one-dimensional pressurised slurry pipelines yet. The design of the True Pipe® in-line sampler is based on the principle of symmetry, as described by Dominique François-Bongarçon7, and also operates on a fail-safe principle for control on the synchronous opening and closing of identical valves for the sample chamber. Previous test work on the True Pipe® in-line sampler indicated that the prototype sampler is reliable within certain tolerances, initially indicating the concept could well be a viable design option. This paper presents the results from further test work, which mainly investigated three sampling phenomena in more detail, by examining classical one dimensional sampling, with the aid of an automated valve actuator. Firstly, the transient effect, which originates from the disruption in laminar particle flow. Secondly, the effect of split sampling, where the portion of the stream is sampled, as well as the full stream. Thirdly, the effect of symmetry is confirmed. The expected accuracy level of the True Pipe® in-line sampler is also evaluated for varied material conditions. Advances on the design include the ability to sample the entire pressurised particulate stream in a safe operating condition, by making use of a mechanical actuator for synchronous opening and closing of the sample chambers, as well as improved control on the valve opening and closing cycles.