Selecting pitot probes for vacuum wind tunnels (10Pa) needs addressing low-pressure measurement sensitivity outgassing and material compatibility factors unique to rarefied gas.Gas Pressure Scanwelcome to click on the website to learn more!
Low-pressure sensitivity needs small holes (0.1-0.5mm) to maximize pressure difference. A 0.3mm hole in a 10Pa tunnel gives 3x better signal-to-noise than a 1mm hole tests showed smaller holes reduced measurement variance by 60%.
Outgassing must be low to not contaminate the vacuum. Titanium and 316L stainless steel have low outgassing rates (<1×10???? Pa·m??/s) better than plastics or aluminum. A vacuum test found aluminum probes released 10x more gas than titanium, needing 2x longer pump-down.
Material must work with vacuum pumps oil-sealed vs dry nickel alloys resist oil backstreaming, dry pumps handle more materials. A space lab uses nickel-plated probes with dry pumps to avoid oil interference.
Probe surface finish (Ra <0.05μm) reduces gas adsorption letting pressure stabilize faster. Polished probes in 10Pa reached stable readings in 5 seconds, rough ones took 15 seconds.
For vacuum wind tunnels prioritize small holes low-outgassing metals and smooth surfaces for accurate low-pressure measurements.