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Level · Interactive Instrumentation Guide
Ultrasonic Tank Level
Move the liquid surface and watch the echo distance, round-trip travel time, level, and current respond.
Custom process schematic · not to scale · blue H connection / orange L connection, where applicable.
Choose length units, then enter LRV and URV. In tank geometry and application settings, set the sensor-to-zero distance to fit your range. Changing units converts existing values.
Tank geometry and application settings
Equation and live calculation
d = c × t / 2; h = H − d; I_ideal = 4 + 16(h − 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
Top-mounted noncontact measurement of distance to a liquid surface.
What the demonstration shows
The pulse travels to the surface and back. Dividing the round-trip path by two gives the distance; subtracting distance from measuring height gives level.
Common mistake to avoid
Real instruments have blocking distances and echo-selection limits. This ideal model excludes foam, turbulence, obstructions, and false echoes.
Model assumptions
Approximate sound speed c = 331.3 + 0.606T_air m/s for dry air from −20 to 60 °C. Humidity, gas composition, echo losses, and blocking distance are excluded.
Technical references
Endress+Hauser — Level measurement principlesNIST — 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.