  Sliding motion between two rough solids under light normal loading involves
myriad micro-impacts between antagonist micro-asperities. Those micro-impacts
are at the origin of many emerging macroscopic phenomena, including the
friction force, the slider's vibrations and the noise radiated in the
surroundings. However, the individual properties of the micro-impacts (e.g.
maximum force, position along the interface, duration) are essentially elusive
to measurement. Here, we introduce an instrumented slider aimed at measuring
the position and the normal component of the micro-impact forces during sliding
against a rough track. It is based on an array of piezoelectric sensors, each
placed under a single model asperity. Its dynamical characteristics are
established experimentally and compared to a finite elements model. We then
validate its measurement capabilities by using it against a track bearing
simple, well-defined topographical features. The measurements are interpreted
thanks to a simple multi-asperity contact model. Our slider is expected to be
useful in future studies to provide local insights into a variety of
tribological questions involving dry rough sliding interfaces.
