An intelligent electronic device having a gain control unit adapted to selectively regulate operating ranges of output signals of a sensing circuit of the device is described. , and a compound represented by the formula :wherein R1 and R2 independently represent a hydrogen atom, a C1-8 alkyl group, or a C5-8 cycloalkyl group, R3 represents a hydrogen atom or a C1-8 alkyl group, and X represents a single bond, a sulfur atom, an oxygen atom, a C1-8 alkylidene group or a C5-8 cycloalkylidene group. Ozone is provided around the workpiece under conditions where the ozone diffuses through the boundary layer and reacts with the material on the first surface. The second signal path digitally filters the process signal and subjects the process signal to less delay than the first signal path.