  In this paper we measure the two-body relaxation time from the angular
deflection of test particles launched in a rigid configuration of field
particles. We find that centrally concentrated configurations have relaxation
times that can be shorter than those of the corresponding homogeneous
distributions by an order of magnitude or more. For homogeneous distributions
we confirm that the relaxation time is proportional to the number of particles.
On the other hand centrally concentrated configurations have a much shallower
dependence, particularly for small values of the softening. The relaxation time
increases with the inter-particle velocities and with softening. The latter
dependence is not very strong, of the order of a factor of two when the
softening is increased by an order of magnitude. Finally we show that
relaxation times are the same on GRAPE-3 and GRAPE-4, dedicated computer boards
with limited and high precision respectively.
