Working Principle of Displacer type level transmitter

Buoyancy force of displacer acts on lever and torqueing tube which are further connected to four thin metal strain gauges as full Whitestone Bridge of electronics amplifier.

The voltage at bridge is directly proportional to effected weight.

This displacer level transmitter works on Archimedes Principal which states that anybody immersed in liquid  is subjected to Archimedes buoyancy force, which is used to determine liquid of level, density and interface.

Liquid level measuring is done by changing buoyancy force considerations.

To calculate buoyancy force use this equation,

FA = Vx ⋅ ρ1 ⋅ g + ( V – Vx ) ⋅ ρ2 ⋅ g

FA= Buoyancy force

V =Volume of displacer

Vx =Volume of medium displaced by measuring body with density ρ1

ρ1 =Average density of heavier medium

ρ2 =Average density of lighter medium

g =Local acceleration due to gravity

FG= Displacer body weight force