Internal pressure gauge for cylinder of combustion engine

摘要

The pressure is measured by a piezoelectric element (3) connected to the gate electrode of an FET (4) whose drain-to-source path earths a current source (I). The signal (Us) produced by the liberated charge carriers passes through a DC blocking capacitor (C) to the non-inverting input of an operational amplifier (2), which is connected to earth via a resistance (R) and switched (S) to a predetermined voltage level (Uo). The switch is opened only for the time needed to evaluate the measurement signal.