Hydrostatic DP Level Transmitter (Head to Level)
The liquid level a hydrostatic (differential-pressure) level transmitter reports from the head it measures: P = 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 and source
level_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.
Hydrostatic (differential-pressure) level measurement (P = 0.433 x SG x H), by name; the transmitter's configured range/calibration and the tank geometry govern.
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