There are several issues that make all our TC systems far from perfect.
One is how accurate the temp is, in other words does the display ever match the actual temperature. That requires calibration, and setting the TCR value for a good match. If you're calibrating using an IR gun, that's got its own issues, like setting the emissivity to match the surface you're reading. And that will even change, as the substance is melting. If you use a thermocouple, it's a bitch to mount. But if you get in the ball park on the readings, you find the match won't cover a wide temp range. You might be dead on at 350 deg F, and off by huge amounts at higher and lower values. The overall resistance change of an unknown heater assembly makes for a crude thermometer. And then, what is the display firmware showing?
Another factor is how well the control algorithm seeks and maintains temp. All control systems have to take into account the lag in effect and make changes gradually enough for the changes to take place and the feedback information (in this case the changing resistance of the heater) to be meaningful. The tradeoff is how fast you can seek target temp vs. how much you'll overshoot and have to keep correcting. This is e.g. where limiting the wattage during ascent is important. A lot of people don't care, they just want fast.
And finally, all the mechanical details, like how completely, and how fast, the temp of the heater is passed to the substance. You might achieve perfect control at the resistive heater, the donut, the coil, and get it improved with better firmware, but the substance usually doesn't see that directly. And temperature that the controller sees it is never even throughout the heater, all it sees is the average resistance of the heater wire. As vapor is pulled, cold air enters, and that cools the source. It's a very complicated system if you wanted to fully compensate for all these variables.
Given these issues, it's unrealistic to expect lab grade temp control in such a crude setup. I'm not sure it's worth tremendous expense or effort. As long as I can limit the temp to below say 440 deg F on hot vapes, or to below 380-400 for lower temp dabs, i'm alright. The Picos can do that out of the box with a little tweaking of the TCR and the ascent wattage limit -- and so can the eVics etc.
I've got SO many other things to tweak around here that I think I'll put off getting deeply into better firmware for my vape mods ;-)
Always interesting to read others' experience and views.
