Electronic Engine Indicators with Special Reference to Some Recent American Designs

Abstract

For internal combustion engines, the mechanical indicator has been largely superseded by “single-point” systems or by electro-mechanical transducers in conjunction with electronic instruments. After dealing briefly with the history of engine indication and some early electronic devices for this purpose, the paper outlines the characteristics of an ideal indicator. Most commercially-available indicators now use a variable-capacitance “pick-up”. Three contemporary systems (two American and one British) of this type are described, with details of the pick-ups, basic circuits, and performance under practical operating conditions. This is followed by a description of a radically different type of pick-up developed in the United States. It uses a catenary-shaped diaphragm and a variable-resistance sensitive element. The improved performance realized by this pick-up is explained by reference to its unique design. In conclusion, the characteristics of all four of the systems described are examined with respect to the ideal indicator.