Wireline Logging wireline measurements, the logging tool (or sonde) is lowered into the open wellbore on a multiple conductor, contra-helically armored wireline cable. Once the tool string has reached the bottom of the interval of interest, measurements are taken on the way out of the wellbore. This is done in an attempt to maintain tension on the cable (which stretches) as constant as possible for depth correlation purposes. (The exception to this practice is in certain hostile environments in