In a method for acquiring data indicating an electrostatic capacitance between a focus ring and a measuring device includes a disc-shaped base substrate, sensor units arranged along an edge of the base substrate and a circuit substrate mounted on the base substrate, a processor acquires one or more first data sets respectively including a plurality of digital values indicating an electrostatic capacitance of a corresponding sensor unit. The measuring device is transferred to a region on the mounting table surrounded by the focus ring. The processor acquires second data sets when one or more digital values or an average of the digital values included in each of said one or more first data sets exceeds a first threshold. The processor stores measurement data including the respective second data sets or averages of the digital values of each of the second data sets. The measuring device is unloaded from the chamber.