CDC provides accurate in-situ pressure measurements and takes two fluid samples per trip in an openhole to provide answers to drilling, production, and reservoir engineering and geological questions. Operated by an electrically driven hydraulic system, the tool can be set and retracted as often as necessary to measure pressure in all zones of interest during one trip. Pretest pressure can be observed by the engineering to determine if the packer has sealed properly and if the fluid flow is adequate to obtain a diagnostic sample. If either condition is questionable, the tool can be retracted and moved to a more suitable test depth. At the surface, formation pressures are recorded on film and displayed in both digital and analog form.