Displacer Level Gauge
One kind of level gauge uses buoyant force to measure liquid level on a nearly stationary object called a displacer.
It is called displacer because its purpose is to displace liquid.A force measuring mechanism senses changes in the buoyant force and converts this force into an indication of level. Displacer provide a continuous measurement over a range determined by their length and can be made into transmitters for automatic level control in shallow vessels.
The displacer move up and down only a little way,perhaps a only a fraction of an inch. As the liquid level changes,the buoyant force moves the displacer slightly and twist the torque tube. The motion of the torque tube moves the pointer to indicate the liquid level on the scale.
The pointer’s total rotation is only 2 to 7 degree.
The amount of pointer rotation depends on the following conditions -
- The Size,Shape and weight of the displacer.
2.The length of the support arm.
3.The stiffness of the torque tube.
4.The density of the liquid.
5.The range variation in the liquid level.
The displacer gauge can be modified to use with a different liquid by replacing the displacer with one of a different diameter. If the new liquid is less dense than the former liquid,the new displacer should have a greater diameter than the previous one. The larger diplacer will displace a greater volume of liquid for the same change in level. However because of the different densities,the greater volume will weigh the same amount as the smaller volume of denser liquid. If the new liquid is more dense than the former liquid,the new displacer should have a smaller diameter.