Maturation, Receiving Area, Fermentation, Process
In an open vessel, the contents are connected to the atmosphere. Any change of ambient pressure causes a change of pressure of the fluid in the vessel. In order to measure the change of the fluid column in the vessel, gauge pressure transmitters or differential pressure transmitters (with open low pressure side) are used to measure hydrostatic pressure in the vessel.
The pressure in a closed vessel can assume any value. In order to measure the true hydrostatic pressure of the volume in the tank, a differential pressure between the head pressure and the total pressure at the bottom of the vessel needs to be measured at the same time.
Therefore, the high pressure side H is connected to the tank bottom and the low pressure side L is connected to the top. This ensures that the differential pressure applied to the transmitter is proportional to the height of the liquid, regardless of the head pressure inside of the vessel.