what is the purpose of measuring differential pressure to measure close tank level in Dp tx
In close tank two level available so with d/p one can measure both level different which is known as level of liquid in close tank.
In open tank only hydrostatic pressure is acting on measuring instrument as per actual water column. For example, open water tank with the height of 5 meter filled full the hydrostatic pressure Acting at the bottom of the tank will be 5000 mm of H2O but if it’s closed tank of crude oil with some unsteady blanketing gas pressure, the hydrostatic pressure acting on the bottom of the tank will vary even when liquid level is steady. That variation is due to blanket gas pressure variation and to compensate that variation DP type device is used… In dp type, the differential is equal to hydrostatic pressure…