I currently use a BLtouch 3.1, which is known to stop operating at about 35-40 °C. In fact, when I preheat the bed at 100 °C close to the probe, I sometimes get issues with the pin not retracting correctly.
I would like in the future to enclose and heat the printer chamber, therefore I need a probe capable of operating at higher temperature. My target is 100 °C.
As of now, I'm aware of this solution:
This high temperature probe uses a mechanical switch in combination with a servo motor to probe the bed. The servo motor is outside the enclosure and retracts the probe pin by pulling on a steel string inside a spring guide tube.
Microswitches are known to work at high temperatures (that's what the link above uses), but usually need a servo or other mechanism to extend/retract them when needed. Servos typically don't operate at such high temperature, not to mention that they are usually not very accurate.
I saw a Hall filament sensor which uses Hall effect sensors "ss49e" and which could be easily modified to be used as bed probe. Those Hall effect sensors are rated up to 100 °C but at that temperature they have up to 8% shift of the null value and +3/-9% change in sensitivity. The linked project uses two of them in differential mode so the temperature compensation should be much better, but it is not clear how much better. A discussion about it on a Russian forum does not talk about this.
Are there other options operating at 100 °C?