BAS Software SolutionsTechnical workflow software
Flow · Interactive Instrumentation Guide
Differential Pressure Flow
Change the pressure drop across a restriction and compare linear DP current with square-root flow current.
Custom process schematic · not to scale · blue H connection / orange L connection, where applicable.
Application settings
Equation and live calculation
Q = Q_ref √(ΔP/ΔP_ref); I_DP = 4 + 16(ΔP − DP_LRV)/(DP_URV − DP_LRV); I_flow = 4 + 16(Q − Flow_LRV)/(Flow_URV − Flow_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
Orifice, nozzle, or Venturi applications under constant-density, fixed-geometry assumptions.
What the demonstration shows
For this ideal normalized model, flow fraction is the square root of DP fraction. Select where extraction occurs: transmitter or receiving system. Enter separate DP and flow signal ranges. The reference DP/flow pair defines the physical square-root relationship; editing signal ranges does not redefine that pair.
Common mistake to avoid
Apply square-root extraction once. A transmitter already outputting flow must feed a linear receiving input. Negative DP does not fit this forward-flow model.
Model assumptions
Normalized flow at fixed density and restriction geometry, with no low-flow cutoff or pressure/temperature compensation. Not an orifice-plate sizing tool.
Technical references
Yokogawa — Square-root extractionNIST — 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.