How is a mmHg measured?
Answer:
With a sphygmomanometer (instrument).
Inches of mercury in a column, or on a gauge. The "mm" refers to a given volume of mercury, and the weight that this volume of this metal has. The pressure, or vacuum needed to move that column is measured in inches for the force needed to move that mass of material.
1 mm Hg = 133.322368 pascals
1 pascal = 9.86923267 × 10-6 atm
Barometer, manometer, pressure gauge.
A long tube is held in a pool of mercury and the atmospheric pressure pushes the mercury into the tube. Then the height of the mercury in the tube is measured in mm.
are you asking about measuring pressure in mm of Hg
typically they use a mercury barometer ... http://en.wikipedia.org/wiki/barometer#m...
it consists of a U shaped tube, filled with mercury ... one end is connected to place where the pressure is to be measured , the other is open to atmosphere... the difference in the height of the level of mercury give the difference in pressure (this is gauge pressure) ...
if the end open to atmosphere is sealed (so that the pressure is zero ...it is vacuum), then the difference in height will be equal to absolute pressure (this way one can measure the atmospheric pressure ... which is tyipcally 760 mm of Hg)
some of the pressure gauges which work on different principle can have a scale marked in mm of Hg ...
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btw if you want to convert "x" mm of Hg to other units (say psi), just search google for
x mm of Hg = ? psi
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