Method and apparatus for providing repeatable wireline depth measurements

Abstract From the Canadian patent

Well logging depth measurement method and system are described for automatically driving a recorder under varying wireline measurement conditions. This system produces two depth signals. First depth signals correspond to magnetic marks placed at regular intervals on the wireline. Second depth signals correspond to incremental movements of the wireline as produced by mechanically coupled measuring devices. Such measuring devices are subject to slippage, variations in circumference etc... There are no, variations of this type for magnetic mark signals but the intervals between these signals are much larger than the mechanically produced incremental signals and are too far apart to be used to …