For experiments using cylinder pressure indication on the CT 400.01 test engine, the normal spark plug is exchanged for a modified spark plug. This modified spark plug is fitted with a micro pressure transducer. The pressure transducer is directly exposed to the combustion chamber pressure when the spark plug is inserted. The spark plug itself retains its full functionality. The core component of the pressure transducer is a heat resistant piezo-electric quartz crystal, which outputs a charge signal proportional to the pressure. The pressure transducer is connected to the measuring amplifier in the CT 400.09 electronic indication system.
