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Pressure · Interactive Instrumentation Guide
Gauge Pressure Transmitter
Change process pressure and see the reference, engineering value, and ideal 4–20 mA signal.
Custom process schematic · not to scale · blue H connection / orange L connection, where applicable.
Application settings
Equation and live calculation
P_abs = P_gauge + P_atm; I_ideal = 4 + 16(PV − 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
Pump discharge or process piping pressure measured relative to local atmosphere.
What the demonstration shows
Gauge pressure is relative to atmosphere. Absolute pressure uses a vacuum reference: P_abs = P_gauge + P_atm. Current follows the configured range.
Common mistake to avoid
Do not mix gauge and absolute ranges. A vacuum is a negative gauge pressure, not a negative absolute pressure.
Model assumptions
Ideal proportional transfer with no damping or measurement error. The teaching model limits current to 4–20 mA; manufacturer-specific saturation and fault-current logic are excluded. Display-unit changes preserve the same physical values.
Technical references
WIKA — Pressure measurement referenceNIST — 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.