Vacuum Pressure Measurement
Da Rough Vacuum un Ultra-High Vacuum
Understand Vacuum UnitaVacuum—pressure below atmospheric—e essential in semiconductor manufacturing, scientific research, food packaging, e many industrial processes. Measuring vacuum requires different units e techniques than positive pressure, con ranges spanning da slight vacuum un pressures approaching absolute zero.
Vacuum Ranges
| Range | Pressure (torr) | Pressure (mbar) | Pressure (Pa) | Applicazioni |
|---|---|---|---|---|
| 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 |
Comuni Vacuum Unita
Torr (mmHg)
Named after Torricelli, 1 torr equivale un 1 mmHg—il pressure that supports un 1mm column di mercury. Widely used in North America, especially in scientific applications.
- Standard atmosphere: 760 torr
- Rough vacuum: 1-760 torr
- High vacuum: millitorr (mTorr) range
Millibar (mbar) / Hectopascal (hPa)
Comuni in Europe e international standards. 1 mbar = 1 hPa. Convenient because 1000 mbar ≈ 1 atmosphere.
- Standard atmosphere: 1013.25 mbar
- 1 mbar = 0.75 torr
Pascal (Pa)
Il SI unit. Standard atmosphere e 101,325 Pa. For vacuum work, milliPascal (mPa) o microPascal (µPa) puo be used.
Conversione Table
| 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 | — |
Conversione Formulas
- Torr un mbar: Multiply da 1.333
- mbar un torr: Multiply da 0.75
- Torr un Pa: Multiply da 133.3
- mbar un Pa: Multiply da 100
Absolute vs Gauge Pressure
Absolute Pressure
Measured relative un perfect vacuum (zero). Scientific vacuum misurazioni usare absolute pressure. Esempio: 10 torr absolute.
Gauge Pressure
Measured relative un atmospheric pressure. In vacuum, gauge reads negative. Esempio: -25 inHg gauge (pollici di mercury below atmospheric).
Convertendo Between Them
- Vacuum absolute = Atmospheric - Vacuum gauge
- -25 inHg gauge = 29.92 - 25 = 4.92 inHa absolute
- Or circa: 760 - (25 × 25.4) = 125 torr absolute
Measuring Vacuum
By Range
| Vacuum Range | Measurement Method |
|---|---|
| Rough (>1 mbar) | Bourdon gauge, capacitance manometer |
| Medium (1-10⁻³ mbar) | Capacitance manometer, Pirani gauge |
| High (10⁻³-10⁻⁷ mbar) | Pirani gauge, cold cathode gauge |
| Ultra-high (<10⁻⁷ mbar) | Hot cathode ionization gauge |
Industry Applicazioni
Semiconductor Manufacturing
Chip fabrication requires ultra-high vacuum (10⁻⁹ mbar) un prevent contamination during deposition processes.
Food Packaging
Vacuum packaging typically uses 1-100 mbar un remove oxygen e extend shelf life.
Scientific Research
Particle accelerators e surface science experiments operate at extreme vacuum (10⁻¹⁰ un 10⁻¹² mbar).
Conclusione
Vacuum pressure e measured in torr, mbar, o pascal, con different ranges requiring different misurazione techniques. Comprendere that 1 torr ≈ 1.33 mbar ≈ 133 Pa helps navigate tra unit systems. Da food packaging at un few hundred mbar un semiconductor fabs at 10⁻⁹ mbar, vacuum technology spans over 15 orders di magnitude di pressure.