What is relative pressure and absolute pressure

The so-called relative pressure is a kind of pressure compared with a certain place, and the absolute pressure is such a large pressure.

Relative pressure: By default, an atmospheric pressure is 0, such as the pressure gauge of the boiler uses relative pressure, the absolute pressure of the vacuum pressure is 0, and the absolute pressure of the barometer is used.

Absolute pressure, or true pressure, is the pressure calculated from absolute zero pressure. or vacuum as the starting point for the calculated pressure. Absolute pressure, referred to as absolute pressure.

Gauge pressure, or relative pressure, or gauge pressure for short, refers to the pressure calculated from the local atmospheric pressure at that time. When the pressure of the measured system is equal to the local atmospheric pressure at that time, the needle of the pressure gauge points to zero. That is, the gauge pressure is zero.

Vacuum, when the absolute pressure of the system being measured is less than the local atmospheric pressure at that time, the difference between the local atmospheric pressure at that time and the absolute pressure of the system is called vacuum. The pressure gauge used in this case is called a vacuum gauge.

See the figure for the relationship between absolute pressure, gauge pressure and vacuum.

a- The pressure point pressure is less than the atmospheric pressure at that time.

b- The pressure point pressure is stronger than the atmospheric pressure at that time.

As can be seen from the figure, when the system p> atmospheric pressure, absolute pressure = atmospheric pressure + gauge pressure.

System p >> Absolute pressure = atmospheric pressure - vacuum.

Absolute pressure refers to the pressure relative to the vacuum.

The relative pressure is based on the local atmospheric pressure at that time.

The pressure calculated for the reference point is also known as the gauge pressure.

The pressure conversion formula PA=PO+PM, PA is the absolute pressure, PM is the relative pressure, and PO is the standard atmospheric pressure.

Relative pressure can be divided into two types according to the relative magnitude of the absolute pressure and the local atmospheric pressure at that time

Gauge pressure: The part of the fluid being tested where the absolute pressure is higher than the local atmospheric pressure at that time.

Gauge pressure = absolute pressure at the local atmospheric pressure at that time.

Vacuum pressure: The part of the fluid being tested where the absolute pressure is lower than the local atmospheric pressure at that time, also known as the vacuum value.

Vacuum pressure shed dust strength = local atmospheric pressure at that time absolute pressure.

Vacuum. It is the ratio of the vacuum value to the local atmospheric pressure at that time.

Vacuum = Vacuum value of the local atmospheric wheel and circular pressure at that time.

First, the reference is different.

1. Absolute pressure: Force refers to the pressure directly acting on the surface of the container or object, that is, the actual pressure on the object, and its zero point is the absolute vacuum, and the symbol is PABS.

2. Xianghong stove slip pair pressure: It is a kind of pressure expressed by atmospheric pressure as a reference, and it is a kind of expression method of pressure.

Second, the calculation method is different.

1. Absolute pressure: Vacuum degree refers to the absolute value of the negative pressure value when the absolute pressure value is less than the atmospheric pressure, and the gauge pressure is negative (that is, negative pressure). The legal unit of pressure is Pa (Pa), and the larger unit is Megapascal (MPa) = 10 6Pa.

2. Relative pressure: atmospheric pressure p. Relative pressure is made for the pressure port u from zero point. That is, the absolute pressure minus the local atmospheric pressure gives the relative pressure value, which is expressed by the letter pq.

Third, the methods of measuring and defending the chaos are different.

1. Absolute pressure: Ordinary industrial pressure gauges measure the gauge pressure value, that is, the pressure difference between the absolute pressure and the atmospheric pressure. When the absolute pressure is greater than the atmospheric pressure value, the measured gauge pressure value is a positive value, which is called positive gauge pressure; When the absolute pressure is less than the atmospheric pressure value, the measured gauge pressure value is a negative value, which is called negative gauge pressure, i.e., the degree of vacuum.

2. Relative pressure: It is a diaphragm pressure gauge that uses electrical methods to measure the deflection of the diaphragm. The diaphragm acts as a plate for the capacitor. The capacitance of a capacitor changes as the diaphragm moves.

Absolute pressure, relative pressure, vacuum.

One is the absolute pressure and the other is the gauge pressure, and the absolute pressure minus the atmospheric pressure is equal to the gauge pressure.

p pgh is actually calculated by the gauge pressure, so the absolute pressure at the beginning of the underwater h must be added to the atmospheric pressure. What should be compared in this question is the absolute pressure, i.e. p1 pgh1 p2 pgh2.

where P1 is the ambient atmospheric pressure, H1 is the depth of the test tube nozzle from the water surface outside the tube, P2 is the gas pressure in the tube, and H2 is the depth of the liquid level in the tube from the nozzle. Obviously, P2 > P1 because the pressure of the water is compressed by the gas in the tube.

The starting point for calculating absolute and relative pressure is different. The absolute pressure starts from the complete vacuum, and the pressure is 0 with the complete vacuum. The relative pressure is measured at atmospheric pressure as a pressure of 0 points. The difference between the two values is one atmosphere. That is: absolute = relative + 1 atmosphere*

:Formula) to adopt (* hee-hee-hee......

Yes. But it can't be called a "formula", the conversion between this is not good to type out with a mobile phone. The computer will send you later.

Relative pressure refers to the difference between the pressure exerted on the object and the pressure of the surrounding medium, while absolute pressure refers to the pressure experienced by the object. The relationship between the two is important in gas pressure.

First, let's look at the definitions of relative pressure and absolute pressure. Relative pressure refers to the difference between the pressure value of the point where the object is located and the pressure value of the surrounding gas, and it is a relative concept. For example, when a balloon is filled with gas, the relative pressure inside the balloon is zero when the pressure of the gas inside the balloon is equal to the pressure of the gas outside the balloon.

Whereas, absolute pressure refers to the pressure experienced by an object, and its value is an absolute quantity. For example, when a balloon is filled with gas, the pressure of the gas inside the balloon is absolute, and the difference between its pressure and the surrounding gas is the relative pressure of the balloon.

Second, let's look at the relationship between the two. In aerodynamics, the absolute pressure is equal to the relative pressure plus the atmospheric pressure. That is, the pressure experienced by an object is equal to the difference between its relative pressure and the pressure of the surrounding gas plus atmospheric pressure.

This relationship is very important for the study of gas pressure.

In conclusion, relative pressure and absolute pressure are two important concepts in gas pressure. The relationship between them is that absolute pressure is equal to relative pressure plus atmospheric pressure. Understanding this relationship is very helpful in mastering gas pressure. <>

Absolute pressure refers to the pressure relative to the positive vacuum, relative pressure refers to the pressure relative to a certain substance, and general relative pressure refers to the atmospheric pressure relative to the standard.

pressure; The pressure conversion formula PA=PO+PM, PA is the absolute pressure, PM is the relative pressure, and PO is the standard atmospheric pressure.