Centimetre of water
Encyclopedia
A centimetre of water is a less commonly used unit of pressure
derived from pressure head
calculations using metrology
. It 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 network
s (then usually in metre
s water column). It is also a common unit of pressure in the speech science
s.
It is 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.
This unit is commonly used to specify the pressure to which a CPAP machine is set after a polysomnogram.
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
derived from pressure head
Pressure head
Pressure head is a term used in fluid mechanics to represent the internal energy of a fluid due to the pressure exerted on its container. It may also be called static pressure head or simply static head...
calculations using metrology
Metrology
Metrology is the science of measurement. Metrology includes all theoretical and practical aspects of measurement. The word comes from Greek μέτρον , "measure" + "λόγος" , amongst others meaning "speech, oration, discourse, quote, study, calculation, reason"...
. It is frequently used to measure the central venous pressure
Central venous pressure
Central venous pressure describes the pressure of blood in the thoracic vena cava, near the right atrium of the heart...
, the intracranial pressure
Intracranial pressure
Intracranial pressure is the pressure inside the skull and thus in the brain tissue and cerebrospinal fluid . The body has various mechanisms by which it keeps the ICP stable, with CSF pressures varying by about 1 mmHg in normal adults through shifts in production and absorption of CSF...
while sampling cerebrospinal fluid
Cerebrospinal fluid
Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...
, as well as determining pressures during mechanical ventilation
Mechanical ventilation
In medicine, mechanical ventilation is a method to mechanically assist or replace spontaneous breathing. This may involve a machine called a ventilator or the breathing may be assisted by a physician, respiratory therapist or other suitable person compressing a bag or set of bellows...
or in water supply network
Water supply network
A water supply system or water supply network is a system of engineered hydrologic and hydraulic components which provide water supply. A water supply system typically includes:# A drainage basin ;...
s (then usually in metre
Metre
The metre , symbol m, is the base unit of length in the International System of Units . Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole , its definition has been periodically refined to reflect growing knowledge of metrology...
s water column). It is also a common unit of pressure in the speech science
Speech science
Speech science refers to the study of production, transmission and perception of speech. Speech science involves anatomy, in particular the anatomy of the oro-facial region and neuroanatomy, physiology, and acoustics.-Speech production:...
s.
It is defined as the pressure exerted by a column of water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
of 1 cm
Centimetre
A centimetre is a unit of length in the metric system, equal to one hundredth of a metre, which is the SI base unit of length. Centi is the SI prefix for a factor of . Hence a centimetre can be written as or — meaning or respectively...
in height
Height
Height is the measurement of vertical distance, but has two meanings in common use. It can either indicate how "tall" something is, or how "high up" it is. For example "The height of the building is 50 m" or "The height of the airplane is 10,000 m"...
at 4 °C
Celsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
(temperature of maximum density) at the standard acceleration of gravity.
This unit is commonly used to specify the pressure to which a CPAP machine is set after a polysomnogram.
| 1 cmH2O | = 98.0638 pascals Pascal (unit) The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre... |
| = 0.01 metres water column or meters, water gauge (m.Wg) | |
| = 10 mm.Wg Millimeters, water gauge mm.Wg means millimeters, water gauge. It is the pressure required to support a water column of the specified height . As a pressure unit it varies with temperature, but approximately 1 mm H2O = 9.8 Pa... |
|
| ≈ 0.98064 mbar Bar (unit) The bar is a unit of pressure equal to 100 kilopascals, and roughly equal to the atmospheric pressure on Earth at sea level. Other units derived from the bar are the megabar , kilobar , decibar , centibar , and millibar... or hectopascals Pascal (unit) The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre... |
|
| ≈ 0.39370 inH2O Inch of water Inches of water, wc, inch water column , inAq, Aq, or inH2O is a non-SI unit for pressure. The units are by convention and due to the historical measurement of certain pressure differentials. It is used for measuring small pressure differences across an orifice, or in a pipeline or shaft... |
|
| ≈ 0.00096781 atm Atmosphere (unit) The standard atmosphere is an international reference pressure defined as 101325 Pa and formerly used as unit of pressure. For practical purposes it has been replaced by the bar which is 105 Pa... |
|
| ≈ 0.73554 torr Torr The torr is a non-SI unit of pressure with the ratio of 760 to 1 standard atmosphere, chosen to be roughly equal to the fluid pressure exerted by a millimetre of mercury, i.e., a pressure of 1 torr is approximately equal to 1 mmHg... |
|
| ≈ 0.73554 mmHg | |
| ≈ 0.028958 inHg Inch of mercury Inches of mercury, ' is a unit of measurement for pressure. It is still widely used for barometric pressure in weather reports, refrigeration and aviation in the United States, but is seldom used elsewhere.... |
|
| ≈ 0.014223 psi Pounds per square inch The pound per square inch or, more accurately, pound-force per square inch is a unit of pressure or of stress based on avoirdupois units... |
External links
- Pressure conversion calculator at Cornell UniversityCornell UniversityCornell University is an Ivy League university located in Ithaca, New York, United States. It is a private land-grant university, receiving annual funding from the State of New York for certain educational missions...
website