Patent ID: 7977939

Claim:
An apparatus: a magnetized engine component, said magnetized engine component being stationary with respect to the engine and establishing a first magnetic field at a top thereof having a first polarity and a second magnetic field at a bottom thereof having a second polarity, said first polarity being the opposite of said second polarity, said first and second magnetic fields varying in response to stress imparted to said component by combustion within the engine; and a magnetic field sensing element spaced from and not in physical contact with said magnetized engine component, said magnetic field sensing element being configured to sense changes in said first and second magnetic fields to provide an output proportional to said stress imparted by said combustion within the engine to indicate a state of said combustion within the engine, wherein said magnetic field sensing element comprises first and second fluxgate sensors connected in differential mode, said first fluxgate sensor being positioned adjacent said top of said magnetized engine component and said second fluxgate sensor being positioned adjacent said bottom of said magnetized engine component.