Small perturbations in the drive voltage are applied at a level to cause {HEAD ~ a measurable variation} in {TAIL ~ the sensor output current} 
Small perturbations in the drive voltage are applied at a level to cause { HEAD ~ a measurable variation } in { TAIL ~ the sensor output current }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL