An electrochemical sensor of a downhole tool positionable in a wellbore penetrating a subterranean formation is provided. The end of the etch process is ascertained by monitoring the electric potential of the substrate to detect a pattern indicative of the end of the etch process. Thus, many XML data files may be processed and loaded simultaneously, which minimizes system memory requirements, improves system reliability and memory management, and reduces processing time required from the start of processing an XML file to completing its loading into a database. Heating chambers in the heating assembly that is sandwiched between the compressor assembly and the expander assembly heats up the working fluid. Queries can then be executed rapidly across any or all index entries in any or all slices.