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A pressure gauge measures atmospheric or gas/liquid pressure. A simple mercury gauge is made using a glass tube. The difference in height of the mercury on two sides of the manometer provides the measurement. A digital gauge is often used in modern pressure measurement applications. Pressure gauges are used in medicine, industry, avionics, and weather forecasting.
A pressure gauge is a device for measuring pressure. This could be atmospheric pressure or the pressure of a gas or liquid. There are many types of pressure gauges, including mercury gauges and digital gauges.
A simple mercury pressure gauge can be made using a piece of glass tube. The tube is sealed at one end, then mercury is placed in the tube such that no air is left at the sealed end of the tube. The tube is then bent into a U shape, with the sealed end at the top of one leg of the U and the open end at the top of the other leg of the U.
As the mercury in the tube moves to the bottom of the U shape, a vacuum is created in the sealed end of the tube. At this end of the tube, there is no air to produce downward pressure on the mercury. The open end of the tube can then be exposed to air or gas, the pressure of which must be measured. The difference in height of the mercury on the two sides of the manometer provides the measurement which can allow the gas pressure to be determined.
Since this way of measuring pressure was used in the early days of physics research, pressure was specified in units of “millimeters of mercury” (mm Hg). A pressure measurement of 1 mm Hg refers to the pressure that will result in a one millimeter difference in a mercury manometer tube. Modern physicists have a new name for measuring pressure, called torr. One torr of pressure is equal to 1 mm Hg.
In addition to measuring pressure, a pressure gauge can also be used to measure the speed at which a stream of air is flowing. Moving air creates a region of lower pressure than normal atmospheric air. The open end of a gas pressure gauge can be placed in an area of airflow to determine the speed of moving air by measuring how the pressure changes.
For modern pressure measurement applications, a digital pressure gauge is often used. In medicine, manometers can be used to measure blood pressure, and small manometers can be used to monitor the pressure in a patient’s airways. Pressure gauges are also used in many industrial settings, avionics and weather forecasting.
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