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