What is Counting Efficiency?
According to ISO 21501-4 “Counting Efficiency (CE) is the ration of the number concentration by a light scattering particle counter (LSAPC) to that measured by a reference instrument for the same test aerosol”.
In context it means that the counting efficiency is the ratio of particles measured by two particle detection instruments. One a particle counter and the other a reference instrument which could be another particle counter with a higher resolution or a Condensation Particle Counter (CPC). CPC’s are widely used to calibrate particle counters.