the present discloses an alternate construction and method for a magnetostrictive probe intended to be used as a tank monitoring device . height determination , either water or fuel , is referenced to an ultrasonic pickup assembly located inside the shaft at the foot of the probe . with this inverse approach , height measurement takes advantage of the relative geothermal stability of underground storage tanks , or the temperature stability offered by the thermal mass of the fuel , to facilitate a more accurate tank level determination . at that new location , the detection circuit gains the added benefits of being isolated from the effect of magnetic risers , large temperature swings and other undesirable phenomenon that often affect magnetostrictive probe measurements that are referenced to the canister . aside from its primary use as referred to by this disclosure , this probe could be adapted for any application necessitating precise knowledge of height or distance measurement in relation to the foot of the probe without using a reference magnet .