An LDMA-FCE (long differential mobility analyzer-faraday cup electrometer) system capable of measuring particle sizes up to larger than 1 mum was developed, and a data reduction process for converting an electrical mobility distribution measured by the LDMA-FCE system into a particle size distribution was derived by the modification of a process previously used for a DMA-CNC (differential mobility analyzer-condensation nucleus counter) system. The performance of the LDMA was evaluated by a tandem DMA system, electrical classification of the PSL standard particles, and field emission-scanning electron microscopy observations. The accuracy of the modified data reduction process was confirmed by comparing particle size distributions measured by the LDMA-FCE system with those determined using an LDMA-CNC system. Particle electrical mobility distributions, as measured by the tandem DMA system, were in good agreement with the theoretical distribution. Good agreement was also found between particle size distributions measured with the LDMA-FCE and the LDMA-CNC systems. Thus, the LDMA-FCE system performed well and represents a useful device for measuring the size of submicron aerosol particles over a wide range.