| 摘要 |
PCT No. PCT/SE97/00087 Sec. 371 Date Sep. 23, 1997 Sec. 102(e) Date Sep. 23, 1997 PCT Filed Jan. 21, 1997 PCT Pub. No. WO97/27400 PCT Pub. Date Jul. 31, 1997A measuring circuit for sensing ionization within a combustion chamber of an engine is arranged in the grounded end of the secondary winding (5) of an ignition coil (2), and includes a voltage source for measurements having a substantially constant potential. The voltage source for measurements used is a capacitor 13 which is charged by the spark current SC, and subsequently after the ignition spark goes out will apply a bias voltage over the spark plug gap 3 with a reversed polarity in relation to the spark voltage. The ionisation within the combustion chamber is detected with a measuring resistance 14 arranged in series with the capacitor 13. A rectifying element 11 is connected in parallel with the measuring resistance, which will secure that the spark current is developed in the spark plug gap 4 and that the measurement current passes through the measuring resistance 14. The rectifying element is grounded with a separated ground strap which does not pass the ground plane of the measuring resistance. The interference inducing spark current may then be conducted in a separated circuit without having to pass the ground plane used for the remaining electronic components of the circuitry. |
