Multichannel data transmission system for rotating elements using a noncontacting slip ring

The collection or acquisition of dynamic data from elements that are rotati ng (e.g., gearing system, axle, engine propeller, and machine tool spindle) is a significant challenge in many engineering applications. Both contacti ng and remote telemetry-based methods have been employed to provide a data bridge between the rotating and stationary reference frames, however these methods suffer from several difficulties. A new method for the transmission of signals from the transducers on a rotating element is presented. Infrar ed light emitting diodes (LEDs) are placed on the circumference of the shaf t or the end of it. Externally mounted photodiodes receive a frequency modu lated light from the LEDs. Signal multiplexing enables multiple-channel sig nal transmission to be realized. The properties of the instrument are as fo llows: dynamic maximum frequency of 50 kHz, static sine distortion degree l ess than 1%, dynamic channel isolation of -40 dB, dynamic linear error less than 1%, and static/dynamic gains of 50-200. The proposed method has been validated through experiments performed on a prototype optical signal trans mission system. Experimental results show excellent agreement with theoreti cal calculations. (C) 2000 American Institute of Physics. [S0034-6748(00)03 911-3].