We show that the timing properties of a pulsed low-energy positron lifetime beam can be conveniently tested by an electron beam. We apply this method to study the time resolution of the beam and electron scattering in flat and 'sawtooth' shaped choppers. The results show that (i) time resolution of 160 ps is obtained, (ii) the scattering of the electrons and the secondary electron yield of the flat chopper make the time resolution worse and background poor, and (iii) both these problems can be solved by using a 'sawtooth' shaped chopper. We also compare these results to beam simulations. (c) 2005 Elsevier B.V. All rights reserved.