How ETH Zurich Engineers Achieved 3.5 mmHg Pressure Waveform Fidelity for an In-Vitro Heart Rig

CUSTOMER & CONTEXT

TONUS is an engineering research project at ETH Zurich developing next-generation, non-invasive blood pressure measurement devices. To validate their optical PPG and ultrasound sensors safely without patient risk, the team built a specialized in-vitro mock circulatory test rig simulating human arterial pulse waves across heart rates from 40 to 120 beats per minute.

THE CHALLENGE

To replicate human blood pressure waves accurately, the test rig required two sealed fluid reservoirs operating on identical pneumatic air cushions. The team’s initial self-built tanks failed to maintain a reliable seal, causing air leakage that corrupted pressure control and prevented the tanks from reproducing matching waveforms. Fitting errors and poor connections on the prototype tanks continuously introduced measurement errors, halting sensor validation.

THE SOLUTION

The team integrated two 2L SR-TEK clear pressure tanks (2000ML-CT-SP358) into the mock circulation loop. Engineered with tight dimensional consistency and standardized connection ports, these vessels provided the leak-free seal required to admit compressed air and vent towards a vacuum supply reliably. The optical transparency of the CT Series vessels allowed engineers to monitor fluid levels visually and purge unwanted air bubbles during filling and de-aeration.

THE RESULTS

• 3.5 mmHg pressure waveform fidelity: Replicated the target pressure waveform with a root-mean-square error (RMSE) of just 3.5 mmHg across heart rates from 40 to 120 bpm within a physiological pressure range of 60-150 mmHg (~8,000 to 20,000 Pa).
• 100% dual-tank synchronization: Completely eliminated pressure control divergence between the two system reservoirs, enabling repeatable dataset collection.
• Zero connection leak errors: Standardized SR-TEK porting completely removed fitting leaks and setup errors experienced with self-built tanks.

CUSTOMER QUOTE

“Our test rig relies on two sealed, pneumatically controlled tanks that both have to reproduce the same pressure waveform, and our own self-built tanks simply could not stay tight or hold that curve reliably. The SR-TEK 2L Clear Pressure Tanks, with their clean connections, removed a whole class of leaks and fitting errors and gave us two tanks that finally behaved identically, which was essential for reaching our test rig milestones.”

— Noah Schürch, TONUS Test Rig Team

CALL TO ACTION

Building a high-precision medical test rig or fluid simulation system? Contact SR-TEK today to discuss your custom pressure vessel requirements or request a quote.