Hydrostatic DP Level Transmitter (Head to Level)

ScopeP = 0.433 x SG x H (0.433 psi/ft is water at ~60 F), so level H = P / (0.433 x SG). A tap reading 4.33 psi in water is 10 ft; the full-span (URV) pressure for a 20-ft tank is 8.66 psi, so 4.33 psi is 50% of span. A denser fluid gives more pressure per foot, so the same 4.33 psi in a 1.2-SG fluid is only 8.3 ft. Assumes an OPEN (vented) tank with the tap at zero level, no elevation/suppression: an elevated dry-leg tap needs zero suppression and a wet-leg (sealed) tank needs zero elevation, both set at calibration, and the SG is at operating temperature. The transmitter's configured range and calibration and the tank geometry govern.

Formula or tablelevel_ft = measured_pressure_psi / (0.433 x specific_gravity); span_psi (URV) = 0.433 x specific_gravity x max_level_ft; level_pct = 100 x level_ft / max_level_ft. 0.433 psi/ft is water at ~60 F.

Source and editionHydrostatic (differential-pressure) level measurement (P = 0.433 x SG x H), by name; the transmitter's configured range/calibration and the tank geometry govern.

Free accessThe hydrostatic head relation is public physics; the 0.433 psi/ft is water's density (62.3 lb/ft^3 / 144), the specific gravity and levels come from the fluid and tank, and the pressure is the transmitter reading.

What governsEstimate. AHJ and licensed professional govern.

API field namesmeasured_pressure_psi, specific_gravity, max_level_ft, level_ft, level_pct, span_psi

• Hydrostatic head level = P / (0.433 x SG); 0.433 psi/ft = water at ~60 F; span = 0.433 x SG x max levelhydrostatics
• Open tank, tap at zero assumes a vented tank, tap at zero level, no elevation/suppression; a dry-leg needs zero suppression, a wet leg zero elevation; SG at operating temperaturelevel-transmitter calibration practice