an ionic current detection means which applies a voltage across {TAIL ~ a pair} of electrodes installed in {HEAD ~ a combustion chamber} of the internal combustion engine, and detects the ionic current flowing between the pair of electrodes through ions generated when the gas mixture in the combustion chamber has burned 
an ionic current detection means which applies a voltage across { TAIL ~ a pair } of electrodes installed in { HEAD ~ a combustion chamber } of the internal combustion engine , and detects the ionic current flowing between the pair of electrodes through ions generated when the gas mixture in the combustion chamber has burned
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH