A measurement amplifying circuit (400) for a piezo-electric sensor (100) positioned in an internal combustion engine supplying a signal to be measured, includes: a module (420) for generating a common mode voltage; a differential amplifier (410); and a subtraction module (430). The module (420) for generating a common mode voltage is to be connected to a wall (111) of the engine, the module (420) for generating a common mode voltage being suitable for supplying a common mode voltage signal (Vcm) reproducing the variations of an engine signal (Sb) received from the wall (111) of the engine.

A disconnection detection circuit includes: a pull-up resistor to which the detection signal is fed and which connects a signal line connected to the wiring cable to a power supply or a pull-down resistor which connects the signal line to a GND; and a voltage clip circuit 105 which includes a high-voltage clip circuit which is connected between the signal line and the power supply and which clips the voltage of the signal line to the maximum specified voltage and a low-voltage clip circuit which is connected between the signal line and the GND and which clips the voltage of the signal line to the minimum specified voltage.

A cylinder internal pressure sensor includes: a housing; a diaphragm having flexibility and being joined to one end of the housing; a sensor element configured to change an output signal according to deformation of the diaphragm; and an opposed member housed inside the housing so as to face the diaphragm. The opposed member defines a housing room between the diaphragm and the opposed member, and includes: a cylindrical tube part being a layered structure with an inner tube and an outer tube; and a seal part provided inside the tube part. The sensor element is fixed to the seal part. The tube part is provided with a spring rate reducing portion that is provided between the diaphragm and a position where the inner tube and the outer tube are joined together.

A system includes an engine control system configured to receive a first vibration signal from a first knock sensor disposed about a reciprocating engine, apply a binaural model to the first vibration signal, derive an engine health condition based on the application of the binaural model to the first vibration signal, and communicate the engine health condition.

In one instance, disclosed herein is an engine system, comprising: an engine comprising a plurality of engine cylinders; and a controller operative to: control a respective ignition timing for each engine cylinder of the plurality of engine cylinders; detect an increase of a knock intensity of the engine; after detecting the increase of the knock intensity of the engine, compare the knock intensity of the engine to a threshold knock intensity; if the knock intensity of the engine is greater than the threshold knock intensity, retard the respective ignition timing for each engine cylinder of the plurality of engine cylinders by the same amount; and if the knock intensity of the engine is less than the threshold knock intensity, retard a first ignition timing of a first engine cylinder by a first amount independently of a second ignition timing of a second engine cylinder.