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