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