There are many ways to measure level.
1.Differential Pressure / Diaphragm Seal
Transmitter measure pressure at the bottom of a tank and converts that pressure to a level reading.
Transmitters emits an ultrasonic pulse and listens for an echo off the top of the material. The time of flight indicates the level in the vessel.
A rod extends down into a tank and measure the conductivity/RF admittance between the probe and the tank wall.As the level changes this electrical value changes and this determines level.
Float transmitter have a float that moves up and down as they float on the surface level.The float position is detected via variety of methods.
- Displacer Transmitter
A displacer has a large float which is connected to a torque tube.As the level rises the float pushes up on the torque tube with increasing force. This force is converted to level.
Weigh cell use strain gauges to measure the weight of a vessel and the material within.Weight is converted to level.
Pulse radar emits a very short burst of radar into a vessel and the same antenna listens for the echo off the top of the material. The time of flight determines the tank level.