അറ്റ്മോസ്ഫിയർ (യൂണിറ്റ്)

അറ്റ്മോസ്ഫിയർ (യൂണിറ്റ്) പ്രമാണ അറ്റ്മോസ്ഫിയർ (ചിഹ്നം: atm) മർദ്ദത്തിന്റെ ഏകകമാണ്. ഇത് 101 325 Pa (1.013 25 bar) എന്ന് നിർണയിച്ചിരിക്കുന്നു. ചിലപ്പോൾ ഇതിനെ അവലംബമായോ പ്രമാണിക മർദ്ദമായോ ഉപയോഗിക്കുന്നു.

ചരിത്രം

മർദ്ദ ഏകകങ്ങളും സമമൂല്യങ്ങളും

Pressure units

ക സ തി	പാസ്കൽ	Bar	Technical atmosphere	Standard atmosphere	Torr	Pounds per square inch
	(Pa)	(bar)	(at)	(atm)	(Torr)	(psi)
1 Pa	≡ 1 N/m2	10−5	1.0197×10−5	9.8692×10−6	7.5006×10−3	1.450377×10−4
1 bar	105	≡ 100 kPa ≡ 106 dyn/cm2	1.0197	0.98692	750.06	14.50377
1 at	0.980665×105	0.980665	≡ 1 kp/cm2	0.9678411	735.5592	14.22334
1 atm	1.01325×105	1.01325	1.0332	1	≡ 760	14.69595
1 Torr	133.3224	1.333224×10−3	1.359551×10−3	1.315789×10−3	≡ 1/760 atm ≈ 1 mmHg	1.933678×10−2
1 psi	6.8948×103	6.8948×10−2	7.03069×10−2	6.8046×10−2	51.71493	≡ 1 lbF /in2

A pressure of 1 atm can also be stated as:

≡1.01325 bar

≡ 101325 pascal (Pa) or 101.325 kilopascal (kPa)

≡ 1013.25 millibars (mbar, also mb)

≡ 760 torr^{[n 1]}

≈ 760.001 mm-Hg, 0 °C, subject to revision as more precise measurements of mercury’s density become available^{[n 2][n 3]}

≈ 29.9213 in-Hg, 0 °C, subject to revision as more precise measurements of mercury’s density become available^{[n 3]}

≈ 1.033 227 452 799 886 kgf/cm²

≈ 1.033 227 452 799 886 technical atmosphere

≈ 1033.227 452 799 886 cm–H₂O, 4 °C^{[n 2]}

≈ 406.782 461 732 2385 in–H₂O, 4 °C^{[n 2]}

≈ 14.695 948 775 5134 pounds-force per square inch (psi)

≈ 2116.216 623 673 94 pounds-force per square foot (psf)

= 1 ata. The ata unit is used in place of atm to indicate that the pressure shown is the total ambient pressure on the system being calculated or measured.^[1] For example, for underwater pressures a pressure of 3.1 ata would mean that the 1 atm of the air above water is included in this value.

Notes:

1. Torr and mm-Hg, 0°C are often taken to be identical. For most practical purposes (to 5 significant digits), they are interchangeable.
2. This is the customarily accepted value for cm–H₂O, 4 °C. It is precisely the product of 1 kg-force per square centimeter (one technical atmosphere) times 1.013 25 (bar/atmosphere) divided by 0.980 665 (one gram-force). It is not accepted practice to define the value for water column based on a true physical realization of water (which would be 99.997 495% of this value because the true maximum density of Vienna Standard Mean Ocean Water is 0.999 974 95 kg/l at 3.984 °C). Also, this “physical realization” would still ignore the 8.285 cm–H₂O reduction that would actually occur in a true physical realization due to the vapor pressure over water at 3.984 °C.
3. NIST value of 13.595 078(5) g/ml assumed for the density of Hg at 0 °C

മറ്റുപയോഗങ്ങൾ

ഇതും കാണുക

• Standard conditions for temperature and pressure
• Atmospheric pressure