Pressure, proven

A cardiac catheter measures pressure from inside the body, threaded to the heart through the femoral artery. Before anyone trusts what it reports, someone has to prove it true. This is the bench that did the proving.

Sketch of the calibration rig: a syringe feeding a stopcock manifold atop the benchtop pressure chamber, transducer cable attached

The stuck thing

Flometrics had a calibration and validation system for in-vivo pressure catheters — the critical measurer in the loop — and it needed to be more trustworthy than it was: better software, and a physical sensor rig whose behavior could be believed.

The diagnosis

The interesting part was the seam. On one side, a benchtop pressure chamber with transducers, tubing, and fluid; on the other, the LabVIEW software controlling it; behind both, the way the catheter is actually used medically. Physical realities rule a rig like this: a single unnoticed air bubble in the fluid path softens the pressure wave and quietly corrupts the calibration.

Made it go

I improved the control software and bench-tested the physical sensor system end to end: LabVIEW control of the chamber, pressure-wave modulation to simulate bodily processes, and controls for the long list of variables that could skew a reading. I worked out and verified precise purge procedures for catheter attachment, so no bubble survived to lie. The reference standards were kept honest too — checked against each other, flagged, and dated.

Whiteboard covered in handwritten calibration steps, waveform sketches, and consistency checks — the calibration and sweep procedure, worked out on the whiteboard

Monitor showing LabVIEW block diagrams and the bridge-sensor channel configuration with a live signal chart — the software side of the seam: LabVIEW, talking to the bridge sensor

Wallace & Tiernan precision pressure gauge beside a dial reference gauge with a note flagging it as reading 3% low — the reference standard, and a gauge flagged “reads 3% low,” dated

The lab bench: oscilloscope showing a pressure waveform, signal generator, and the glass calibration chamber — the lab: where the physical rig and the software met

bench testing & metrology · LabVIEW instrumentation · calibration procedure design · the physical–software seam

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