Fig. 12 shows a comparison of velocity profiles measured in bentonite 6.9% w/w (K = 0.006, n = 1, τy = 9) at a flow rate of 0.4 l/s (Re2 = 1900). The same observations can be made between the results obtained using the standard and delay line transducers. In the case of measuring in fluids with a yield stress the cavity distorts profiles (diamonds) more significantly due to the high velocity gradients present close to the pipe walls. When comparing the profiles before and after deconvolution (crosses and circles), it can be seen that the deconvolution procedure improved the velocity data close to the wall significantly. The velocity profiles shown after implementing the deconvolution procedure also show better agreement with the theoretical profiles, calculated using the rheology obtained from in-line tube viscometry.