Scientific, surveying, optical, weighing, measuring, signaling, checking and supervision apparatus and instruments, namely, apparatus and instruments for metering fluid levels, recording fluid levels and for calculating fluid level data; scientific or measuring apparatus and instruments for testing or studying liquid levels on a physical or chemical basis and optical and electrotechnical apparatus, included in this class, in particular those used for mining technology, oil technology, drilling technology and conveying technology, and navigation, namely, well sounders, liquid level sounders, portable liquid level sounders, depth sounders, acoustic well sounders, and sonic fluid level meters; measuring apparatus for determining liquid levels; pre-recorded compact discs, DVDs and other digital recording media containing operating software; data processing equipment, computers; computer software for generating data, generating fluid level reports, generating graphs, archiving data, displaying data, analyzing data, transferring data, storing data, printing documents, printing tables or printing graphs; apparatus for recording, transmission or reproduction of sound or images; apparatus for measuring compression of oil, gas, deep-water and geothermal wells; pressure and temperature probes for deep well drilling; apparatus for extracting samples and apparatus for transporting samples, included in this class, namely, sampler apparatus for collecting physical samples of sand from a well, down hole fluid samplers, surface samplers for oil and gas wells; instruments for monitoring rod depth points, namely, dynamometers