The base pneumatic valve positioner which utilizes a unique spool valve, is a cam characterized, force balanced instrument that is simple, rugged, and very user friendly for calibration and maintenance. The NEMA 4 X housing is cast aluminum, with an electrostatically applied polyester coating for excellent resistance against a wide range of environmental conditions. This unit operates on a standard 3-15 instrument signal (12 psi span-optional 24 psi), and can provide years of trouble free service in many tough applications. The gauge block is cast into the unit and therefore standard. The large indicator has scaling to operate in both direct and reverse directions.