An apparatus and method for operating and calibrating a paint mixture delivery system includes a positive displacement fluid cylinder and a linear transducer that monitors operation of the positive displacement fluid cylinder. A controller is connected to a servo drive whose operation manipulates the performance of the positive displacement fluid cylinder. Operation of the fluid delivery system is controlled such that the ratio of paint or resin to catalyst or hardener can be accurately controlled and calibration of the discrete fluid flow sensors can be quickly and conveniently calibrated to assure delivery of the respective fluids are the desired mixture ratio.