AT902 Automated Filter Tester is a universal tester developed in accordance with the standards of NIOSH 42 CFR 84 and EN 149:2009. It is mainly used to detect the filtration efficiency of particulate respirators and the filtration efficiency and resistance of materials. A high-precision photometer is used as the detector to ensure accurate results. The tester is divided into two categories: oil mist and salt mist. The oil mist tester uses DEHS as the aerosol, while the salt mist tester uses NaCl. The solution is sprayed through a Ruskin nozzle and dried to form an aerosol. The system adopts precision instruments to control flow and concentration, and communicates with the computer through system integration. It has good stability and is easy to operate. The results are calculated by detecting the upstream and downstream concentrations and using the formula. The airflow can be monitored in real time through an electric proportional valve and a flow meter to ensure the accuracy and stability of the test flow. The aerosol concentration can be monitored by an electric proportional valve and a differential pressure gauge to provide stable test particles. The filtering material tester is a fully automatic instrument that can be controlled by a computer to perform the following actions: ▲It can automatically feedback control and read all working parameters, including volume, resistance, test time and efficiency. ▲Measure the particle count and resistance of the sample during a test period. ▲Display operating parameters. ▲The system uses serial communication to initiate the transfer of data files.