The electronics
module uses a feedback loop between the sensor coils and the shaker coil to maintain the tubes
in a continuous state of resonant oscillation. This resonant frequency changes with process fluid
density, since the effective mass of the fluid-filled tubes changes with process fluid density, and
mass is one of the variables influencing the mechanical resonant frequency of any elastic structure.
Note the “mass” term in the following formula, describing the resonant frequency of a tensed string