{HEAD ~ The current} is then measured between {TAIL ~ the electrodes} at the plurality of voltages and a contamination level is determined using the measured currents 
is measured between
{ HEAD ~ The current } is then measured between { TAIL ~ the electrodes } at the plurality of voltages and a contamination level is determined using the measured currents
HEAD HEAD HEAD HEAD HEAD HEAD REL OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH