The fuel quantity cadensicon is used during refueling operations to measure the characteristics of fuel entering the right inner tank. It is only interrogated "after" 881Lbs (400Kg) has entered the tank.
The cadensicon measures fuel dielectric constant and density.
A failure of this unit usually results in dashes in the second decimal of each tank quantity. This is a "soft" failure which is a slight degradation of quantity indication, but perfectly safe for flight. The crews will bitch about the dashes which can be cleared by pressing the "Reset/Memory Clear" button on the fuel quantity computer for a minimum of 10 seconds, (Ref AMM 28-42-44-02-99
If they write it up)
The unit is located just inboard of the fueling nozzles.
Mounting plate with unit removed.
Back of unit.
The preferred "weapons" were a 3/8" open end wrench and a 1/4" socket with a six inch extension. The silver drive rod (visible in top image) had to be pulled forward slightly to wiggle the cadensicon out of the wing.