BAS Software SolutionsTechnical workflow software
Level · Interactive Instrumentation Guide
Open-Tank Hydrostatic Level
Enter your report LRV and URV to check the calibrated span, or select physical tank geometry to explore hydrostatic level.
Custom process schematic · not to scale · blue H connection / orange L connection, where applicable.
Tank geometry and application settings
Equation and live calculation
ΔP = ρg(h − z); DP_empty = −ρgz; DP_full = DP_empty + ρgH; I_ideal = 4 + 16(ΔP − LRV)/(URV − LRV)
Live substitution appears when the demonstration loads.
PV = process value; LRV/URV = lower/upper range values; I = current in mA. Pressure calculations use kPa internally. Selected units apply to inputs, limits, diagrams, and readouts; changing units converts the same physical values without changing the current. Tank calculations use meters internally; z is positive above the bottom tap. ρ = 1000 × specific gravity in kg/m³; g = 9.80665 m/s². H in tank equations means measured height, not the H port. Entered LRV/URV define the current scaling; calculated empty/full tank DP values are reference checks. Set and Reset Points define switch operation; deadband is their absolute difference. Temperature reference equations use °C internally. Mercury pressure units use conventional NIST conversion factors. Vacuum entries are negative gauge pressure; the absolute-pressure readout remains nonnegative. Models assume ideal instantaneous response. Displayed current is limited to the nominal 4–20 mA range: I_display = clamp(I_ideal, 4, 20), where clamp holds a value at its lower or upper limit. This teaching limit does not reproduce manufacturer-specific saturation or alarm currents.
Where it is used
Vented tanks where atmospheric pressure is the low-side reference.
What the demonstration shows
The low side is vented. Hydrostatic pressure depends on liquid depth, density, and the elevation of the transmitter. Entered-range mode interpolates applied DP between your LRV and URV; the tank graphic represents calibrated span. Geometry mode calculates physical tank DP independently. LRV and URV alone cannot define actual tank height or density.
Common mistake to avoid
A transmitter below the bottom tap reads a positive mounting head even at zero measured level: zero suppression.
Model assumptions
Constant densities, hydrostatic equilibrium, completely filled liquid impulse lines, and no gas-column head. The upper tap is at the top of the measured span; zero level is the bottom tap. Change vapor pressure to see cancellation in a closed vessel.
Technical references
Emerson — Differential pressure level measurementNIST — SI unit conversion factors (conventional mercury units)Educational model. Consult the instrument manual for installation, configuration, limits, and approved test procedures. No connection to live plant equipment is made.