A method and apparatus for digitizing a signal. The present invention is a multi-phase steel sheet excellent in hole expandability characterized in that:the steel sheet contains, as chemical components in mass, C: 0. The logging system comprises a logging tool. Further techniques are disclosed for calibrating the trimmable capacitance to minimize step size error for the capacitor bank. Electrolysis is used to make the alkali metal ions in the alkali metal enriched glass material combine with electrons from the silicon cathode to form neutral alkali metal atoms in the one or more holes. The deciding includes comparing a bit value of one or more required components of the previous storage key to respective predefined allowed stale value for the required component, and leaving the previous storage key in local processor cache if the bit value of the required component in the previous storage key equals the respective predefined allowed stale value for the required component.