Vacuum Pressão Medição
De Rough Vacuum to Ultra-High Vacuum
Understand Vacuum UnidadesVacuum—pressure below atmospheric—é essential in semiconductor manufacturing, scientific research, food packaging, e muitos industrial processes. Measuring vacuum requires diferente unidades e techniques than positive pressure, com ranges spanning from slight vacuum to pressures approaching absolute zero.
Vacuum Ranges
| Range | Pressão (torr) | Pressão (mbar) | Pressão (Pa) | Aplicações |
|---|---|---|---|---|
| Rough/Low vacuum | 760-1 | 1013-1.3 | 101,325-133 | Vacuum packaging, degassing |
| Medium vacuum | 1-10⁻³ | 1.3-10⁻³ | 133-0.1 | Vacuum drying, freeze drying |
| High vacuum (HV) | 10⁻³-10⁻⁷ | 10⁻³-10⁻⁷ | 0.1-10⁻⁵ | Thin film coating, electron microscopes |
| Ultra-high vacuum (UHV) | 10⁻⁷-10⁻¹² | 10⁻⁷-10⁻¹² | 10⁻⁵-10⁻¹⁰ | Particle accelerators, semiconductor fab |
Comuns Vacuum Unidades
Torr (mmHg)
Named after Torricelli, 1 torr é igual a 1 mmHg—o pressure esse supports a 1mm column of mercury. Widely usado in North America, especially in scientific aplicações.
- Padrão atmosphere: 760 torr
- Rough vacuum: 1-760 torr
- High vacuum: millitorr (mTorr) range
Millibar (mbar) / Hectopascal (hPa)
Comuns in Europe e international standards. 1 mbar = 1 hPa. Convenient because 1000 mbar ≈ 1 atmosphere.
- Padrão atmosphere: 1013.25 mbar
- 1 mbar = 0.75 torr
Pascal (Pa)
O SI unidade. Padrão atmosphere é 101,325 Pa. For vacuum work, milliPascal (mPa) ou microPascal (µPa) may be usado.
Tabela de Conversão
| Torr | mbar | Pa | psi (below atm) |
|---|---|---|---|
| 760 | 1013 | 101,325 | 0 (atmospheric) |
| 100 | 133 | 13,332 | 12.8 below atm |
| 10 | 13.3 | 1,333 | 14.5 below atm |
| 1 | 1.33 | 133 | 14.67 below atm |
| 0.1 | 0.133 | 13.3 | — |
| 0.001 | 0.00133 | 0.133 | — |
| 10⁻⁶ | 1.33×10⁻⁶ | 1.33×10⁻⁴ | — |
Conversão Formulas
- Torr to mbar: Multiply by 1.333
- mbar to torr: Multiply by 0.75
- Torr to Pa: Multiply by 133.3
- mbar to Pa: Multiply by 100
Absolute vs Gauge Pressão
Absolute Pressão
Measured relative to perfect vacuum (zero). Scientific vacuum medições use absolute pressure. Exemplo: 10 torr absolute.
Gauge Pressão
Measured relative to atmospheric pressure. In vacuum, gauge reads negative. Exemplo: -25 inHg gauge (inches of mercury below atmospheric).
Converting Entre Them
- Vacuum absolute = Atmospheric - Vacuum gauge
- -25 inHg gauge = 29.92 - 25 = 4.92 inHa absolute
- Or aproximadamente: 760 - (25 × 25.4) = 125 torr absolute
Measuring Vacuum
By Range
| Vacuum Range | Medição Method |
|---|---|
| Rough (>1 mbar) | Bourdon gauge, capacitance manometer |
| Medium (1-10⁻³ mbar) | Capacitância manometer, Pirani gauge |
| High (10⁻³-10⁻⁷ mbar) | Pirani gauge, cold cathode gauge |
| Ultra-high (<10⁻⁷ mbar) | Hot cathode ionization gauge |
Indústria Aplicações
Semiconductor Manufacturing
Chip fabrication requires ultra-high vacuum (10⁻⁹ mbar) to prevent contamination during deposition processes.
Food Packaging
Vacuum packaging typically uses 1-100 mbar to remove oxygen e extend shelf life.
Scientific Research
Particle accelerators e surface ciência experiments operate at extreme vacuum (10⁻¹⁰ to 10⁻¹² mbar).
Conclusão
Vacuum pressure é measured in torr, mbar, ou pascal, com diferente ranges requiring diferente medição techniques. Understanding esse 1 torr ≈ 1.33 mbar ≈ 133 Pa helps navigate entre unidade systems. De food packaging at a poucos hundred mbar to semiconductor fabs at 10⁻⁹ mbar, vacuum technology spans over 15 orders of magnitude of pressure.