US Patent 7610806 Electronic level gage assembly

A thermowell extends downwardly into tank liquids from the roof of the tank. A magnetostrictive wave guide probe is positioned on the inside of the thermowell and a magnetic float is slidably positioned on the outside of the thermowell. The probe is connected to a head unit containing the necessary electronics for operability which is positioned outside of the tank. The position of the float, and thus the liquid level, is remotely sensed by the probe, and the probe can be removed from the thermowell if necessary without breaking the seal of the tank.