How do you use Siemens differential pressure transmitter as a level transmitter and what are the parameter setting i have to do?

Answer 1

what is suppression in transmitter The pressure P = Force / Area as you know. Now think of a liquid column in the tank, the bottom area of that is 1 cm2. The unit of pressure depends on the way you will follow: 1- This is the illustrative one as in physics books. Force in Newton and Pressure in Pascal (N/m2). ΔP [N/m2] = h [cm] * Specific Weight [N/cm3] / Area [cm2] Specific Weight defined as density times gravity: SW[N/m3] = ρ[kg/m3] * g[m/s2] Let the tank is full of water. Then ρ = 1000 kg/m3 ( @1 bar and 4oC !) and g = 9.8 m/s2 and h=720 cm. This yields: SW = 1000*9.8 = 9800[N/m3] = 9800*10-6[N/cm3] Now the pressure: ΔP = 720[cm] * 9800*10-6 [N/cm3] = 720*9800*10-6 [N/cm2] = 720*9800*10-6*104 [N/m2] ΔP = 70560 pascal = 0.706 Bar = 706 mbar 2-The more practical way: We will use kg-force (kgf)as the unit of force and tecnical athmosphere (at) as the unit of pressure. ΔP [kg/cm2] = h[cm]*ρ[g/cm3]. With ρ= 1 gr/cm3 we will find: ΔP = 720[gf/cm2] = 720*10-3 [kgf/cm2] = 0.72 at ( ≈ 0.7 bar) The "bar", "at", "atm" are the pressure units those are very close each other.(Take a look at Wikipedia for pressure units). In fact u can use the h directly as pressure unit, like ρ*7200 mmH2O. For both method it is essential that u must use true density value! that is the value at pressure and temperature of your tank. Say tank is full of oil then ΔP will be 0.9*0.7 bar why i assumed ρ = 0.9 gr/cm3 for oil. You can obtain only an avaraged value for pressure since the tank contains liquids those have different density values.