This simulator models a full pressure calibration loop: a hand pump and Bourdon reference gauge apply pressure through an isolation/vent manifold and an oil-filled diaphragm to a transmitter, which converts sensed pressure into a 4–20 mA request that a powered receiver decodes back into a pressure reading. Adjust applied pressure, sensor reference, range, calibration errors, damping, manifold path, loop voltage, burden and wire resistance, then trace exactly where the signal is gained, lost or trapped.
• A real-time 3D cutaway of the hand pressure calibrator, Bourdon reference gauge, isolation/vent manifold, isolation diaphragm and fill path, transmitter head with circuit board and terminals, DC loop power supply, and burden resistor/receiver, with home view, focus-selected-part, full-enclosure/cutaway toggle, exploded view, auto-rotate, expand and show/hide numbered labels matching a companion diagram. • Thirteen live controls: applied gauge pressure, sensor reference (gauge/ambient or absolute/vacuum), ambient absolute pressure, lower range value, calibrated span, calibration zero error, calibration span error, transmitter damping, manifold path (process connected / isolate-trap / vent to ambient), loop supply voltage, receiver burden resistance, total wire resistance, and loop condition (closed loop / open conductor). • Play/pause, single-step and larger-step time controls, plus a playback-speed selector. • Start/stop trial, step-applied-pressure and vent-source-to-zero-gauge actions, with a live "what is happening" sequence narrative, operating state, switch-state tokens and a scrollable cell-readings table. • Ten live metrics: applied gauge pressure, process absolute pressure, trapped/connected gauge pressure, transmitter pressure estimate, requested loop current, delivered loop current, transmitter terminal voltage, receiver voltage, receiver decoded pressure, and receiver error against the selected reference. • A Curves & measurements tab with two charts (applied/transmitter/receiver pressures, and requested vs. delivered current), the full model equations, and snapshot measurements. • An Experiments tab with four guided scenarios (midscale calibration, loop voltage shortage, absolute reference, trapped sensing cavity), a model-verification bench of independent automated checks, and a timestamped event log with a copyable trial report. • A Learn & assess tab with guided lessons, a knowledge-check quiz and a written scope/reference statement.
The transmitter converts sensed pressure into a requested current with Irequest = clamp(4 + 16(Pestimate − LRV)/span, 3.8, 20.5) mA, so 4 mA always represents the configured lower range value, not a universal zero. But requesting a current is not the same as delivering it: the loop's available current is Icapacity = max(0, (Vs − 12 V)/(Rburden + Rwire)), which requires at least 12 V of headroom at the transmitter after the burden resistor and wire resistance take their share. Reduce supply voltage or raise burden and wire resistance enough, and the loop simply cannot deliver the requested current — the receiver then decodes a pressure that has nothing to do with what the transmitter actually sensed.
The manifold path adds a second way for a correct sensor to report a stale value: isolating the manifold traps whatever pressure was present at that moment at the transmitter, so the reference gauge continues tracking the live applied pressure while the transmitter no longer does — exactly the scenario the trapped-sensing-cavity experiment is built to expose.
Selecting an absolute reference adds ambient pressure to the applied gauge pressure per Pabsolute = Pgauge + Pambient, so a transmitter configured for absolute reference reports a higher number at the same applied gauge pressure than a gauge-referenced one would — the reference Bourdon dial itself still reads gauge pressure regardless of which reference the transmitter uses. Calibration zero and span errors are applied as an affine shift on top of the ideal transfer function, letting you see how a small span or zero error propagates all the way through to the receiver's decoded pressure and the reported error metric.
The stated scope notes this uses generic first-order sensing and damping with a simplified affine calibration-error model and a stated 12 V compliance requirement — it does not model HART communication, intrinsic-safety barriers, real diaphragm mechanical stress or any specific manufacturer's accuracy class, and fault/saturation currents are illustrative settings rather than a universal standard.
On this simulator, 4 mA always represents the configured lower range value (LRV), following Irequest = clamp(4 + 16(Pestimate − LRV)/span, 3.8, 20.5) mA — it is not a universal zero-pressure signal, and 4 mA can correspond to a nonzero pressure if the range is configured that way.
Delivering the requested current requires headroom: Icapacity = max(0, (Vs − 12 V)/(Rburden + Rwire)), meaning the loop supply must exceed 12 V at the transmitter after subtracting voltage dropped across the burden resistor and wire resistance. If supply voltage is too low or burden/wire resistance too high, the loop cannot deliver the requested current, and the receiver decodes an incorrect pressure even though the transmitter's pressure sensing is functioning correctly.
Gauge pressure is measured relative to ambient atmospheric pressure, while absolute pressure includes it: Pabsolute = Pgauge + Pambient. The simulator lets you configure the transmitter for either gauge or absolute reference; note that the reference Bourdon gauge component always displays gauge pressure regardless of which reference the transmitter itself is configured to use.
This model uses generic first-order sensing and damping, a simplified affine calibration zero/span error, and a stated 12 V loop compliance requirement. It does not model HART communication, intrinsic-safety barriers, real diaphragm membrane stress, or any specific manufacturer accuracy class, and the fault/saturation current values used are illustrative teaching settings rather than a universal industry standard.