Robert W. Burrahm

Development of piston temperature telemetry system

Abstract The measurement of piston temperature in a reciprocating engine has historically been a very time-consuming and expensive process. Several conditions exist in an engine against which measurement equipment must be protected. Acceleration forces near 2000 Gs occur at Top Dead Center (TDC) in automotive engines at rated speed. Operating temperatures inside the crankcase can range to near 150°C. To allow complete mapping of piston temperature, several measuring locations are required in the piston and data must be obtained under various engine operating conditions. Southwest Research Institute (SwRI) has developed a telemetry-based system that with stands the harsh environments mentioned above. The device is attached to the underside of a piston and temperature data is transmitted to a receiving antenna in the engine crankcase. The key element of this device is a tiny power generator which utilizes the reciprocating motion of the piston to generate electricity, thus allowing the transmitter to be self-powered. Thick-film hybrid circuit construction techniques have been used to keep the package size small. This paper covers the development of the power generator, multiplexer and transmitter circuits, and the receiver system. Sample data is included from two automotive engines.