Arhi continues his quest for soldering iron driver perfection. In the latest development, he attached a temperature sensor to the tip of his Hakko soldering iron, and compared the temperature between the tip and the sensor inside the heater. The readings on the graph he posted are almost identical below 50C, but there is a lot of noise coming from the heater sensor above that temperature. He is currently trouble-shooting this issue.
Via the forum.
solved :D
http://dangerousprototypes.com/2011/11/23/soldering-iron-driver-update/