> They use a high mghz signal to measure the tip temperature using impedance measurements IIRC. Then they control the tip temperature using a feedback control loop.
That's not how Metcal fixed temp induction soldering irons work. They don't have a control loop, which is what makes them so much better than other soldering irons.
They exploit the Curie temperature [1] of some alloys, in which the metal loses its inductive properties when it hits a certain temperature. A Metcal power supply pumps a simple 13.56 Mhz signal into the tip which heats it up and when it reaches its Curie temperature, it just stops heating. Since the signal is constant, whenever the temperature of the tip drops it just heats back up without any PID loop. The downside is that you have to switch tips (alloys) with a pair of pliers to change temperatures, but the upside is that there is no control loop delay.
It's also why their station are so reliable. There's basically no "modern" electronics in them and the worst you have to do to fix them is replace an electrolytic capacitor. I've got a power supply manufactured in the late 90s that's still as good as new and like you said, going back to a Hakko or any other soldering iron is downright painful.
(Side note to anyone who cares: when the patents expired, a couple of Metcal engineers left to form Thermaltronics, which sells cheaper stations and Metcal-compatible tips)
Thanks for filling in how the metcal's work! The 13.56 mghz signal made me figure an impedance measurement. Though as you say that explains why metcals are so bulletproof.
Side note: I found Thermaltronics stations to not be much cheaper than Metcal ones. At least for the lower end stations. Gotta love capitalism.
That's not how Metcal fixed temp induction soldering irons work. They don't have a control loop, which is what makes them so much better than other soldering irons.
They exploit the Curie temperature [1] of some alloys, in which the metal loses its inductive properties when it hits a certain temperature. A Metcal power supply pumps a simple 13.56 Mhz signal into the tip which heats it up and when it reaches its Curie temperature, it just stops heating. Since the signal is constant, whenever the temperature of the tip drops it just heats back up without any PID loop. The downside is that you have to switch tips (alloys) with a pair of pliers to change temperatures, but the upside is that there is no control loop delay.
It's also why their station are so reliable. There's basically no "modern" electronics in them and the worst you have to do to fix them is replace an electrolytic capacitor. I've got a power supply manufactured in the late 90s that's still as good as new and like you said, going back to a Hakko or any other soldering iron is downright painful.
(Side note to anyone who cares: when the patents expired, a couple of Metcal engineers left to form Thermaltronics, which sells cheaper stations and Metcal-compatible tips)
[1] https://en.wikipedia.org/wiki/Curie_temperature