Improved fiber optic pressure sensor systems.

摘要

The invention is related to numerous improvements for fiber optic measuring systems, and principally those utilizing a deformable diaphragm for sensing pressure. One aspect of the invention is providing temperature compensation for diaphragm characteristics. Temperature measurement can be achieved by using a light signal having a wavelength distribution which overlaps the cut-off characteristics of a filter positioned at the fiber sensing end. Shifting in the cut-off characteristic in response to temperature modulates the intensity of the reflected back temperature compensation signal. In another approach, temperature is measured through its differential effect on light signals having different launching conditions. With either approach, the temperature measurement is used to calibrate the output of the pressure sensitive diaphragm. Another feature of the invention is particularly oriented to automotive engine combustion chamber pressure measurement. Periodic recalibration of the system can be achieved by measuring pressure at a time when the combustion chamber pressure is known to be close to ambient. For the automotive engine environment, a sensing tip shielding technique is also described using a sintered metal porous plug, which reduces temperature fluctuations experienced at the sensing tip and shields the sensing tip from corrosive materials. A technique for compensation of a fiber optic pressure sensor is described which does not directly measure temperature. In that method, a referencing wavelength is partly reflect and partly transmitted past a filter coating at the sensing end of the optical filament. This invention also describes techniques for multiplexing a number of pressure sensors and a pressure sensing tip having an enclosed volume acting on one side of the diaphragm. <IMAGE>