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Testing Beyond Waterproof: How Our MEMS Pressure Sensors Prove Their Reliability
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Short answer: IP ratings alone don’t predict survivability in chlorinated, hot, humid water. We run a combined-stress protocol—chlorine + hydrostatic load + elevated temperature + humidity + cycling—and then verify post-stress output at ~100 kPa, room temperature. In our internal testing, units met our acceptance criteria for output stability and sealing after 40 full sequences.
Why “waterproof” isn’t enough
“Waterproof” labels typically refer to brief submersion per ingress tests. Chlorinated water, sustained pressure, heat, and humidity act together and can drive drift or seal degradation. Our approach deliberately stacks those stressors to evaluate margin, not just ingress.
What we test (and how we talk about it—precisely)
Combined-stress sequence (internal program)
| Step | Condition | Purpose | How we state it correctly |
| Chlorine immersion under hydrostatic load | Water dosed to ~35 ppm free chlorine; sealed tank pressurized to simulate 0.5 m H₂O ≈ 4.9–5.0 kPa; tank held in 60 °C oven | Accelerated chemical + pressure + thermal stress | 35 ppm is a hyperchlorination/shock level (exception handling), not normal operation; 0.5 m→kPa conversion stated explicitly |
| Humidity aging | 60 °C / 60 % RH for 7 h | Moisture-heat coupling on materials/seals | This is an internal method, not a JEDEC/IEC standard (e.g., it is not 85/85) |
| Post-stress verification | Output checked at ~100 kPa, RT | Drift check vs specification | Use ~100 kPa as a conventional reference point—no implication of formal NTP calibration |
| Endurance | 40 full sequences | Extended exposure emulation | Internal target, not a published cross-industry requirement |
Chlorine levels—operational reality vs our stress
| Water context | Typical free chlorine | What it means for design |
| Potable water distribution | ≪ 1 ppm | Minimal oxidative burden most of the time |
| Recreational pools/spas (normal) | ≈ 1–3 ppm | Routine exposure for wearables/pool hardware |
| Shock/hyperchlorination (exception) | ~35 ppm | Our test level to build margin for edge cases |
We do not claim that all applications see 35 ppm; we include it to represent exception events and accelerate chemical stress.
Acceptance language (what we will—and won’t—say)
- Do say: “Devices met our internal acceptance criteria for output stability and sealing after 40 sequences of the described protocol.”
- Don’t say: “Certified” or “industry-standard pass” unless a third party is involved.
- Do say: “Protocol is internal; conditions differ from public exemplars (e.g., 85/85).”
- Don’t say: “40 cycles required by industry.”
Hydrostatic pressure math (kept tight)
Depth-to-pressure used here: 0.5 m H₂O ≈ 4.9–5.0 kPa. Stated plainly; no hand-waving.
What this means for engineers selecting our parts
PUI offers MEMS pressure sensors, including water-resistant/waterproof SKUs appropriate for contact with treated water when properly integrated (gasketing, vent strategy, materials compatibility). The combined-stress protocol above helps us screen designs intended for pools/spas, potable systems, outdoor enclosures, and wearables that may encounter both routine (1–3 ppm) and exceptional (~35 ppm) chlorine scenarios. Results cited here are our internal data from the stated conditions.
At-a-glance: protocol vs everyday use
| Dimension | Our internal test | Typical operating exposure | Why it’s tougher |
| Chemistry | ~35 ppm free chlorine | 1–3 ppm pools; ≪ 1 ppm potable | Accelerated oxidation/corrosion potential |
| Pressure | 0.5 m H₂O (≈ 5 kPa) | Shallow submersion/splash | Sustained hydrostatic load |
| Temperature | 60 °C hold | Ambient to warm | Speeds reactions and diffusion |
| Humidity | 60 % RH @ 60 °C | Ambient swings | Moisture ingress + thermal synergy |
| Duration | 15 h chem/pressure/heat + 7 h humidity per cycle; 40 cycles | Intermittent, varied | Repetitive stress accumulation |
| Verification | Output at ~100 kPa, RT | Field calibration/monitoring | Explicit drift detection point |
Implementation notes (practical, not theatrical)
- Treat IP as a starting point only; validate chemistry + heat + pressure + humidity together for the intended use case.
- If your application never sees shock dosing, you can derate the chemical leg—but verify with your water authority.
- Always define a post-stress reference point (we use ~100 kPa, RT) and a numeric drift limit tied to your spec.
- Seal stacks and vent paths should be reviewed for chlorine-exposed elastomer compatibility.
Bottom line
Our sensors aren’t just “waterproof.” They are evaluated against stacked, realistic stressors with explicit verification of post-stress behavior. That’s the level of evidence you should demand before putting a MEMS pressure sensor into chlorinated, hot, humid, pressurized environments.
If you want this rewritten around a specific PUI MEMS part number (model-level), send it over—we’ll slot in part-specific limits, acceptance thresholds, and any IP/chemical compatibility notes.