The Pegasor Particle Sensor (PPS) is a small and lightweight sensor that can be used directly in raw exhaust to provide the mass and number concentration of exhaust aerosol. Its operation principle is based on the electrical charging of exhaust aerosol and determination of particle concentration by measuring the charge accumulated on the particles. In this paper we have applied the PPS in a variety of vehicle exhaust configurations to evaluate its performance characteristics. First, the output signal of the instrument was calibrated with diesel exhaust to deliver either the mass or the number concentration of exhaust aerosol. Linear response with the soot mass concentration measured by a Photo Acoustic Soot Sensor and number concentration measured by an Electrical Low Pressure Impactor was established. Based on this calibration, the instrument was then used to measure particle concentrations at levels produced by a gasoline direct injection vehicle and diesel exhaust filtered by particle filters of variable efficiency. Hence, the complete range of concentrations and particle characteristics typically encountered in automotive exhaust has been examined. The results show that the PPS signal can provide a repeatable measurement of aerosol concentration in the exhaust of current vehicles, offering a very good correlation both to the mass and number of particles, as measured by existing techniques.