5.3 Differential Pressure Measurements we When the columns of fluids are at equilibrium (see Figure 5.3), the relationship among pl. pz. p and the heights of the various columns of fluid is as follows: ...5.3 P, +pedig = P + pa da g+p3 dag 1 Fluid 3. Ps Fluid 1, PE + Fluid 2. Pz Figure 5.3 Manometer with three fluids. 42