NOVELTY - The apparatus (100) has a fluid container (150) coupled to a flow line. A surface (166) includes a condition affecting sensor information provided by a sensor (108). A fluid transport mechanism (106) moves fluid (154) from the container into the flow line and causes the fluid to contact the surface. A processor (130) adjusts an operation of the transport mechanism based on the sensor information and baseline information (158). The processor moves the fluid and changes the condition until the fluid is depleted or the sensor information conforms to the baseline information to a selected degree.    USE - Apparatus for conditioning a sensor e.g. optical sensor, densitometer and resistivity sensor (all claimed), of a downhole tool e.g. pumped formation evaluation tool and reservoir description tool, utilized in an electronic system e.g. personal computer (PC), tablet PC, set-top box (STB), personal digital assistant (PDA), cellular telephone, web appliance, network router, switch or bridge, TV, workstation, radio, video player and signal processing for geothermal tools and smart transducer interface node telemetry system. Can also be used for an optical fluid identification (OFID) subsystem sensor, a pressure gauge sensor, a pressure transducer sensor, a strain gauge sensor, a bubble point sensor, a compressibility sensor, a speed of sound sensor, an ultrasonic transducer, a viscosity sensor and a optical density sensor utilized in a vehicle.    ADVANTAGE - The apparatus verifies quality of sensor measurement data in situ, so that accuracy of acquired information and client satisfaction can be increased. The apparatus provides a structure and properties of geological formations to reduce cost of drilling wells for oil and gas exploration. The apparatus allows a major constituent to drill a fluid filtrate, so that formation fluid can be pumped and filtered to reduce contamination. The pump reciprocates the fluid to ensure good fluid mixing and sensor contact in an efficient manner.    DETAILED DESCRIPTION - The transport mechanism comprises a unidirectional/bidirectional pump, an accumulator and a chamber valve (114). The fluid is selected from a group consisting of salt, acid, an organic emulsifying agent, aromatic dye and an oxidizing agent. INDEPENDENT CLAIMS are also included for the following:    (1) a system for conditioning a sensor    (2) a processor-implemented method for conditioning a sensor.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic block diagram of an apparatus for conditioning a sensor.    Apparatus for conditioning sensor (100)    Fluid transport mechanism (106)    Sensor (108)    Chamber valve (114)    Processor (130)    Fluid container (150)    Fluid (154)    Baseline information (158)    Surface (166)