comparing the present rate signal with the reference rate signal to detect when {HEAD ~ the computed rate} of {TAIL ~ change} exceeds the reference rate signifying that the liquid has begun to boil; and 
of
comparing the present rate signal with the reference rate signal to detect when { HEAD ~ the computed rate } of { TAIL ~ change } exceeds the reference rate signifying that the liquid has begun to boil ; and
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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH