I am a user just like you. Maybe you want to change the “Logging Interval” not the sampling rate. On the screen where the measured values are displayed, pressing settings in upper right corner, then Logging Interval, then select 1min or whatever you want, then press upper left arrow to go back to main display. The logging interval of 1min will write one timestamp, chan1 value, chan2 value to the SD card every one min. If the app display is not active while logging, the meter will sleep more to extend battery life.