The measurements of the particle counter are based on the number of particles sampled over a period of 60 seconds, and the default measurement interval is 10 minutes. Establish a maintenance connection to AQT400. See Connecting to AQT400 with RS-232 (CLI). Set the measurement interval in minutes. Measurement interval defines how often AQT400 takes measurements. To define the measurement interval to be 3 minutes, type the following: set lpc_int=3 write --really Measurement interval 3 ... 255 minutes, default 10 minutes.