an ionic current detection means which applies a voltage across a pair of {HEAD ~ electrodes} installed in {TAIL ~ 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 
installed in
an ionic current detection means which applies a voltage across a pair of { HEAD ~ electrodes } installed in { TAIL ~ 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 OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL 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