litebulbs:
WhyIsThereAir:
So I guess a lower voltage is applied on the ground (ie: V/2 = P/4) to mitigate overheating, but it's still not optimal. One of the advantages of having temperature sensing and closed loop control is more capable bite in terms of ice detection, heating element or temp sensor failure. Agreed, the simplest solution may do the job 90% of the time and should be the most reliable since there are fewer parts, but in my experience, the electronics part of any modern system design is usually the most reliable, assuming conservative design rules. The problems are nearly always with the mechanical bits and of course connectors.
As for resistance elements, most of the commonly available resistance wires have only a small positive tempco. For example, nichrome is around 300 ppm per degree C, so they must be using some pretty fancy alloys for the function to get the (?) square law characteristics required.
Chris