I am trying to measure the height [level] of the water in a box that goes from -3°C (saltwater) with water and 150°C dry. Objects will be placed inside the box but will not take up the whole area.
I need a sensor that is robust enough to go through those temperatures and measure accurately. I was thinking of using a float switch on a worm gear, but the motor couldn't stand the heat...
What other methods/sensors are there? I also have a clear tube that runs outside of the tank meant for visually inspecting the height of the water.
Can I use a ultrasound sensor to measure water level? is a closely related question but focuses upon ultrasound. That won't work for my particular case because the contents of the box are effectively unknown. And capacitive techniques won't work either as the box will be grounded.