SENSOR DEVICE FOR DETECTING PHYSICAL PARAMETER IN COMBUSTION CHAMBER OF INTERNAL COMBUSTION ENGINE

To determine proper operation of a combustion sensor, and to normalize the output signals derived from a pick-up having a window exposed to the combustion chamber (10) by compensating for soiling, contamination, and loss of transmissivity of the window due to combustion residue, soot, or the like, a reference light source is provided introducing reference light of a predetermined level to the pick-up, for example when no light is generated due to combustoin events. In an internal combustion (IC) engine, the reference light can be energized during stopped condition of the engine, or during portions of the stroke of the engine when no combustion event takes place. Output signals from the pick-up are applied to a variable amplification factor amplifier, the amplification factor of which is first calibrated with a clean light source, and then continuously recalibrated or normalized with respect to its original calibration by changing the amplification factor in accordance with electrical signals derived from sensing of the reference light, so that the actual sensing light will be normalized with respect to the reference. The calibration, itself, can be variable and account for external factors, such as aging or decrease of light output of the light source. The reference light can be introduced by an externally operated incandescent filament or by shining light into a portion of a tubular housing, for example through a glass light guide, and reflecting the reference light into the sensing window which also senses light due to combustion.