In life, we often encounter situations when there is a need to measure pressure: arterial, atmospheric or pressure of compressed air or gas in a pipe. Let's see what kind of physical quantity it is. And immediately the following question arises: what is the pressure measured in? It turns out that there are several types of units of measure applied to this physical quantity. In this article, we will examine how pressure is measured. So, let's get started, consider each of these units.
The officially recognized International SI system is the unit of pressure Pascal (Pa), its derivatives are kilopascal (kPa) and megapascal (MPa). One Pascal is equal to the following ratio: 1 Pa = 1 N / m 2 . However, different industries use different pressure units. For example, when determining gas productivity and compressed air flow (in compressor technology) several completely different units of measurement can be used.
Let’s figure out how to measure the pressure of gas and air. The main unit used is cubic meter per minute of time (m 3 / min). Often you can find such units as liter per minute (l / min) or atmospheric pressure (atm), and in English-speaking countries they can use cubic foot per minute - cubic foot perminute, or CFM. Let's look at the ratio of these values. 1 l / min corresponds to 0.001 m 3 / min, and 1 CFM is equal to 28.3168 l / min, or 0.02832 m 3 / min. Accordingly, 1 m 3 / min is equal to 35.314 CFM. Very often, performance is given for suction or for normal conditions (1 atm at a temperature of 200 Celsius). In this case, the unit of measurement is set to the letter "n", which means normal conditions. For example, 10 nm 3 / min.
Also, such units can be used to measure pressure: mmHg. Art. (Torr) - millimeter of mercury; atm. - physical atmosphere; at. - technical atmosphere; bar. In English-speaking countries , a value such as pounds per square inch - PSI (pounds per square inch) can be used.
Consider the ratio of the basic units of pressure measurement: 1 megapascal is 10 bar or 7500.7 millimeters of mercury, or 9.8692 physical atmospheres, 10.197 technical atmospheres, as well as 145.04 PSI.
So we figured out how pressure is measured in various areas of technology. And what instruments are used to measure such physical quantities?
These mechanisms are classified by the type of measured pressure (for example, atmospheric, excess or rarefied, that is, vacuum), and, of course, according to the principle of action (liquid, membrane, electric, spring and combined). The most important parameter that characterizes an instrument for measuring air pressure is the accuracy class. There are many such mechanisms. Here are the main devices that are most often used when measuring air pressure:
- aneroid barometer, used to measure atmospheric pressure;
- a barothermic hygrometer is also used to measure atmospheric pressure;
- liquid manometers - used for measuring the pressure difference;
- analog and digital pressure gauges.
To summarize, we say that knowledge of pressure units can be useful to any modern person.