Raw size-Distribution data from twin-DMPS system (Aalto et al., 2001), where the nano-DMA (measuring up to 40 nm, short Hauke type DMA) is quipped with two detectors: a TSI 3776 and a modified Airmodus A20 (Kangasluoma et al., 2015) Data acquired during in March-May 2017 at the SMEAR II station in Hyytiälä, Finland. Data associated with the publication Stolzenburg, Laurila et al. (2023), Atmos. Meas. Techn., "Improved counting statistics of an ultrafine differential mobility particle size spectrometer system" Files DMYYDDMM_A20.Dat contain the raw DMPS data, with YYMMDD indicating the day of the measurement. Data are provided alternating between data acquired with the nano-DMA and with the long-DMA, on a scan by scan basis. First line of each scan cycle (for both DMAs) always indicates the start and end times of the voltage scan. Second line gives the parameters related to the DMPS as given below: (sheath flow in [l per min], aerosol flow in [l per min], DMA inner electrode diameter in [m], DMA outer electrode diameter in [m], DMA classification length in [m], other parameters) Following lines give (for long-DMA): set voltage at DMA [in V], concentration measured by TSI3772 in [per cm3] (for nano_DMA): et voltage at DMA [in V], concentration measured by TSI 3776 in [per cm3], concentration measured by mod. Airmodus A20 in [per cm3] File dmps_data_format_specifier.text gives a conversion from voltage to diameter and indicates the measurement time at each voltage during the stepping of the DMPS. Needs to be used to convert measured concentrations in counts per set-interval. Files GR_J_overview.xlsx gives size-distribution derived quantities during that campaign. Header defines Date, Growth Rate and Formation Rate measured at different sizes [in nm] and by the two different CPCs connected to the nano-DMA. Growth rates in [nm per h], formation rate in [per cm3 per s]. Other data related to the campaign can be obtained from the corresponding author upon reasonable request. juha.kangasluoma@helsinki.fi References: Stolzenburg, Laurila et al. "Improved counting statistics of an ultrafine differential mobility particle size spectrometer system", Atmos. Meas. Techn., in press, 2023 Aalto et al., "Physical characterization of aerosol particles during nucleation events", Tellus B, vol. 53, pp. 344-358, 2001 Kangasluoma et al., "Sub-3 nm Particle Detection with Commercial TSI 3772 and Airmodus A20 Fine Condensation Particle Counters", Aerosol Sci. Techn., vol. 49, pp. 674-681, 2015