PROBES SPAN-3
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PROBES SPAN-3 |
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for print
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The operative embodiment of a probe with centering hold-down tool SPAN-3 is developed and tested in "Compass plus" Ltd. Its trials have shown full advantage over the best probes with one-lever hold-down tool already when recording a vertical component of a wave field. The vertical component of wavefield recorded by the SPAN-3 probe (fig. b) differs by the greater regularity; the first breaks of a direct wave are selected more precisely.
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Additional case history of advantages of SPAN-3 probe are results of the spectral analysis of the direct wave recorded in three sequential points of observation at depths 620 m, 640 m and 660 m (blue, red, green colors accordingly), shown in figures. Distinctions in stability of reception conditions of probes SPAN-3 and ASPU are discovered directly on a direct wave records.
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On records made by the SPAN-3 probe (fig. Ю) the waveform practically does not vary in range 20 mc at all depths and the amplitude of a signal is naturally decreasing with depth. It indicates that conditions of reception remain stable in all points of observation. On records made by the ASPU probe (fig. b) the waveform varies at once from the beginning of record; amplitude of the signal recorded at depth 640 m more than at depth 620 m that it is possible to explain by modification of reception conditions caused by construction of a hold-down. Even greater distinction of records can be detected at comparison of amplitude spectra of these signals.
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It is visible from figure, that amplitudes of spectra component of the signals registered by probes SPAN-3 and ASPU, achieve same level on frequency ~100 Hz and 85 Hz accordingly. It testifies that the centering hold-down of probe in a hole ensures undistorted reception of signals in wider frequency range. As additional affirming of the marked fact analysis of corresponding phase spectra of signals which graphs are shown at the bottom of figure can serve.
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These graphs show, that phase spectra of the signals obtained by the probe ASPU (fig. e), on frequencies ~85 Hz and are above are similar to records of random process. Graphs of phase spectra of the signals obtained by the probe SPAN-3 are differ from each other insignificantly and are described by smooth enough function that confirms persistence of reception conditions of oscillations by the SPAN-3 probe. Thus the results mentioned above display advantages of borehole probe with a rigid centering hold-down even at recording a vertical component of wave field.
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