A Submersible Data Acquisition Unit (“The Sub”) measures and records AC and DC voltage at various points on a vehicle traveling through an electrocoat tank. Condition of the anolyte cells and the rectifier can be determined from data gathered by the Sub. Optimum anolyte cell location can also be determined from the data. Electrocoat film build on the vehicle can be derived for the different probe locations using Sub data. The Sub also provides an insight into the behavioral characteristics of voltage in an electrocoat tank. Data collected from the laboratory, an automotive body line and a parts line will be discussed.