Английская Википедия:Centimetre or millimetre of water
Шаблон:Short description Шаблон:Use British English
A centimetre or millimetre of water (US spelling centimeter or millimeter of water) are less commonly used measures of pressure based on the pressure head of water.
Centimetre of water
Шаблон:Infobox unit A centimetre of water (US spelling centimeter of water)[1] is a unit of pressure. It may be defined as the pressure exerted by a column of water of 1 cm in height at 4 °C (temperature of maximum density) at the standard acceleration of gravity, so that Шаблон:Nowrap = Шаблон:Nowrap × Шаблон:Nowrap × 1 cm = Шаблон:Nowrap ≈ Шаблон:Nowrap, but conventionally a nominal maximum water density of Шаблон:Nowrap is used, giving Шаблон:Nowrap.
The centimetre of water unit is frequently used to measure the central venous pressure, the intracranial pressure while sampling cerebrospinal fluid, as well as determining pressures during mechanical ventilation or in water supply networks (then usually in metres water column). It is also a common unit of pressure in the speech sciences. This unit is commonly used to specify the pressure to which a CPAP machine is set after a polysomnogram.
Шаблон:Nowrap = 98.0665 pascals[2] = 0.01 metre water (mH2O), metre water column (m wc) or metre water gauge (m wg) = 10 mm wg = Шаблон:Val mbar or hPa ≈ Шаблон:Val inH2O ≈ Шаблон:Val atm ≈ Шаблон:Val torr ≈ Шаблон:Val mm Hg ≈ Шаблон:Val inHg ≈ Шаблон:Val psi
Millimetre of water
Шаблон:Infobox unit Millimetre of water (US spelling millimeter of water)[3] is a unit of pressure. It may be defined as the pressure exerted by a column of water of 1 mm in height at 4 °C (temperature of maximum density) at the standard acceleration of gravity, so that Шаблон:Nowrap = Шаблон:Nowrap × Шаблон:Nowrap × 1 mm = Шаблон:Nowrap ≈ Шаблон:Nowrap, but conventionally a nominal maximum water density of Шаблон:Nowrap is used, giving Шаблон:Nowrap.
Шаблон:Nowrap = 9.80665 pascals[2] = 0.001 metre water (mH2O), metre water column (m.wc) or metre water gauge (m wg) = 0.1 cm wg = Шаблон:Val mbar or hPa ≈ Шаблон:Val inH2O ≈ Шаблон:Val ≈ Шаблон:Val torr ≈ Шаблон:Val mmHg ≈ Шаблон:Val inHg ≈ Шаблон:Val psi
In limited and largely historic contexts it may vary with temperature, using the equation:
- P = ρ·g·h/1000,
- where
- P: pressure in Pa
- ρ: density of water (conventionally 1000 kg/m3 at 4 °C)
- g: acceleration due to gravity (conventionally 9.80665 m/s2 but sometimes locally determined)
- h: water height in millimetres.
The unit is often used to describe how much water rainwear or other outerwear can take or how much water a tent can resist without leaking.
See also
References
External links
- Pressure conversion calculator at Cornell University website
- ↑ NOTE: A centimetre of water is abbreviated as cmШаблон:H2O or cm H2O.
- ↑ 2,0 2,1 nist.gov – Guide for the Use of the International System of Units (SI) page 47, 2008 Edition
- ↑ NOTE: Millimetre of water is also sometimes addressed as : millimetres water column, abbreviated as mmwg, mmH2O, or mmwc.
