determining {HEAD ~ a reference value Ro} relative to {TAIL ~ an internal resistance Ri} of the tank, an upper limit Ro+r and a lower limit 
determining { HEAD ~ a reference value Ro } relative to { TAIL ~ an internal resistance Ri } of the tank , an upper limit Ro+r and a lower limit
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH