Engine Combustion Pressure Monitor

The pressure receiving part of the SEC combustion pressure sensor is not a diaphragm structure, but a pipe structure that is closed at the the top. A thin metal strip is attached a a certain tension to the external surface of the pipe.  The tension of the metal strip changes in accordance with pipe length (L), which changes under pressure.  The metal strip vibrates under the excitement generated by the coil unit and the amplifier connected to the cable.  Its vibration frequency is the natural frequency determined by the tension on the metal strip.  As the length of the pipe (L) increase under pressure (P), the tension on the metal strip increases, thus causing the natural frequency to increase.  Because there is a proportional relationship between the applied pressure and the natural frequency of the

　　　　　　　　　　　　　　　　　　　　　strip, it is possible to determined the pressure by measuring

　　　　　　　　　　　　　　　　　　　　　changes in the frequency of the strip's vibration.