What is vacuum degree?

Question 1: What is vacuum degree? In theory, there is no matter in the volume, but there is no real vacuum in reality. Usually, the pressure in the container is lower than the normal atmospheric pressure (10 1325Pa), which is called vacuum state.

Vacuum degree: refers to the pressure below normal atmospheric pressure (10 1325Pa). It is authoritative that Lanzhou Institute of Physics divides the vacuum state below normal atmospheric pressure into five types:

Low vacuum: 100000Pa- 100Pa.

Medium vacuum: 100 pa -0. 1Pa.

High vacuum: 0. 1Pa-0.0000 1Pa.

Ultra-high vacuum: 0.00001pa-0.000001pa

Extremely high vacuum: less than 0.0000000 1Pa.

Pa means pressure. Written writing and instrument display are as follows: for example, 100000Pa is written as 10E 5Pa (read as 10 to the fifth power Pa, usually read as 65438+ million pa); 0.0 1Pa is written as 10E -2Pa (read negative 2 of 10, usually read negative 2 of 1.0).

Question 2: What is a vacuum? Vacuum degree? How many representatives are there? Vacuum refers to the gas state in which the pressure in a given space is lower than 10 1325 Pascal (that is, the standard atmospheric pressure is about 10 1KPa). Vacuum = atmospheric pressure-absolute pressure

As the name implies, vacuum degree is the degree of vacuum. It is the main parameter of vacuum pumping equipment such as vacuum pump, micro vacuum pump, micro air pump, micro suction pump and micro suction pump. The definition of vacuum degree is absolute gas pressure. The microscopic formula of pressure tells us that pressure depends on the number density of gas molecules and the average speed of thermal motion, which can reflect the vacuum degree of the system. The higher the vacuum degree, the lower the absolute pressure, which is usually expressed by "high vacuum degree" and "low vacuum degree". High vacuum degree means "good" vacuum degree, and low vacuum degree means "poor" vacuum degree.

There are usually two ways to identify the degree of vacuum:

First, it is marked by "absolute pressure" and "absolute vacuum" (that is, how much pressure is higher than "theoretical vacuum");

In practice, the absolute pressure of vacuum pump is between 0 ~ 10 1.325 kPa. The absolute pressure value needs to be measured by an absolute pressure meter. At 20℃ and altitude = 0, the initial value of the instrument (absolute vacuum gauge) used to measure the vacuum degree is 10 1.325KPa (i.e. a standard atmospheric pressure).

The second is to distinguish between "relative pressure" and "relative vacuum" (that is, how much pressure is lower than "atmospheric pressure").

Relative vacuum refers to the difference between the pressure of the measured object and the atmospheric pressure of the measuring place. Measure with a common vacuum gauge. In the absence of vacuum (that is, under normal pressure), the initial value of the table is 0. When vacuum is measured, its value is between 0 and-10 1.325 kPa (generally expressed as a negative number).

Question 3: What are vacuum and vacuum degree? When the pressure in the container is lower than atmospheric pressure, the part below atmospheric pressure is called vacuum. Represented by the symbol "pv". This relationship is:

PV = PATM-PA (1-3) Power plants sometimes express the vacuum value as a percentage, which is called vacuum degree. Vacuum degree is the percentage of the ratio of vacuum value to atmospheric pressure, that is:

Vacuum degree = =pv/patm× 100%%

( 1―4)

The vacuum degree in complete vacuum is 100%. If the absolute pressure of the working medium is equal to atmospheric pressure, the vacuum degree is zero.

For example, the mercury vacuum gauge of the condenser reads 7 100mmHg, and the atmospheric pressure gauge reads 750 mmHg. What is the absolute pressure and vacuum in the condenser?

According to pa = (patm-PV)/735.6 = (750-710)/735.6 = 0.054at = 0.0051MPa vacuum = PV/pamb×100% = 7/kloc.

Question 4: How to calculate the vacuum degree? There are usually two ways to identify the degree of vacuum. One is to identify the vacuum degree by absolute pressure, and the other is to identify the vacuum degree by relative pressure.

The so-called absolute pressure means that the vacuum pump is connected to the detection container, and the pressure in the container will not continue to drop and maintain a certain value after a long time of continuous vacuum pumping, so the gas pressure in the container is the absolute pressure of the pump. There is absolutely no gas in the fruit container, so the absolute pressure is zero, which is a theoretical vacuum state. In practice, the absolute pressure of vacuum pump is between 0 ~ 10 1.325 kPa. The absolute pressure value needs to be measured by an absolute pressure meter. At 20℃ and altitude = 0, the initial value of the instrument is 10 1.325KPa. In short, the air pressure marked in the theoretical vacuum is called "absolute pressure" or "absolute vacuum".

Relative vacuum refers to the difference between the pressure of the measured object and the atmospheric pressure of the measuring place. Measure with a common vacuum gauge. In the absence of vacuum, the initial value of the table is 0. When vacuum is measured, its value is between 0 and-10 1.325 kPa (generally expressed as a negative number). For example, if the measured value is -30KPa, it means that the pump can be pumped to a vacuum state that is 30KPa lower than the atmosphere where it is measured. The relative pressure measured by the same pump in different places may be different, because the atmospheric pressure measured in different places is different, which is caused by different objective conditions such as altitude and temperature. In short, the atmospheric pressure marked by "the atmospheric pressure at the measuring place" is called "relative pressure" or "relative vacuum".

Absolute pressure is the most commonly used and scientific method in the international vacuum industry. Because the method of measuring relative vacuum is simple, the measuring instruments are common, easy to buy and cheap, so it is widely used. Of course, in theory, the two can be converted to each other. The conversion method is as follows: absolute pressure = absolute value of air pressure-relative pressure at the measurement place.

Question 5: What is vacuum degree? Automobile engine test and inspection;

1. Start test: In order to make the test results accurate, it is necessary to keep the engine at a high temperature. If the engine can't run because of a fault, it can also be measured when the car is cold, but the accuracy will be reduced. When measuring, close the throttle, cut off the ignition system, connect the vacuum gauge to the intake manifold behind the throttle, and start the engine. Observe that the vacuum gauge value should be between 1 1 and 2 1 kPa. If it is lower than 10 kPa, the possible reasons are: low engine speed (weak starter), worn piston ring (loose seal), stuck throttle or stuck throttle.

2. Idle speed test: When the engine with good performance runs at idle speed, the vacuum gauge value should be stable between 60 and 60~70 kPa. Low and stable vacuum If the vacuum reading is below normal and stable, the possible reasons are as follows. Ignition timing is delayed, valve timing is delayed (timing belt or timing chain is too loose), and camshaft lift is insufficient. If the vacuum gauge drops from the normal value and returns at idle speed, the swing vacuum will swing back and forth rhythmically. The possible reasons are: individual valve hairpin or a camshaft is seriously worn, such as the vacuum gauge swinging between 52 and 52~67 kPa, and the possible reasons are: the valve spring is not hard enough. If the vacuum gauge swings back and forth between 38 ~ 6 1 kPa, the reasons are usually: air leakage of the valve, damage of the cylinder gasket, damage of the piston and strain of the cylinder tube.

The above values are for reference only, because the vacuum degree of the engine will change with the altitude and air density, and the standard value of each engine will be different, and the vacuum degree will also change under different working conditions. Therefore, before fault analysis, we should refer to the normal values of the same type of engine for comparison and comprehensive analysis.

Question 6: What is the vacuum produced when the gas pressure in a vacuum container is lower than atmospheric pressure, also called negative pressure? There is no space for any substance at all (that is, the vacuum degree of 100% is called absolute vacuum, which is very difficult to achieve). Usually 760 mm Hg (0 degree) can be used as a standard scale. If the indicated container reads below atmospheric pressure, it is called vacuum degree. The pressure value (vacuum degree) indicated on the vacuum degree is the pressure difference between the gas pressure in the container and the atmospheric pressure, also called vacuum pressure or low pressure. The lower the atmospheric pressure in the container, the higher the vacuum degree; The higher the atmospheric pressure in the return container (not exceeding 1 atmospheric pressure), the lower the vacuum degree; If the air pressure in the container is equal to atmospheric pressure, then the vacuum degree is zero, that is, there is no vacuum.

Question 7: What is the vacuum degree? In theory, there is no matter in the volume, but there is no real vacuum in reality. Usually, the pressure in the container is lower than the normal atmospheric pressure (10 1325Pa), which is called vacuum state.

Vacuum degree: refers to the pressure below normal atmospheric pressure (10 1325Pa). It is authoritative that Lanzhou Institute of Physics divides the vacuum state below normal atmospheric pressure into five types:

Low vacuum: 100000Pa- 100Pa.

Medium vacuum: 100 pa -0. 1Pa.

High vacuum: 0. 1Pa-0.0000 1Pa.

Ultra-high vacuum: 0.00001pa-0.000001pa

Extremely high vacuum: less than 0.0000000 1Pa.

Pa means pressure. Written writing and instrument display are as follows: for example, 100000Pa is written as 10E 5Pa (read as 10 to the fifth power Pa, usually read as 65438+ million pa); 0.0 1Pa is written as 10E -2Pa (read negative 2 of 10, usually read negative 2 of 1.0).

Question 8: What is a vacuum? Vacuum degree? How many representatives are there? Vacuum refers to the gas state in which the pressure in a given space is lower than 10 1325 Pascal (that is, the standard atmospheric pressure is about 10 1KPa). Vacuum = atmospheric pressure-absolute pressure

As the name implies, vacuum degree is the degree of vacuum. It is the main parameter of vacuum pumping equipment such as vacuum pump, micro vacuum pump, micro air pump, micro suction pump and micro suction pump. The definition of vacuum degree is absolute gas pressure. The microscopic formula of pressure tells us that pressure depends on the number density of gas molecules and the average speed of thermal motion, which can reflect the vacuum degree of the system. The higher the vacuum degree, the lower the absolute pressure, which is usually expressed by "high vacuum degree" and "low vacuum degree". High vacuum degree means "good" vacuum degree, and low vacuum degree means "poor" vacuum degree.

There are usually two ways to identify the degree of vacuum:

First, it is marked by "absolute pressure" and "absolute vacuum" (that is, how much pressure is higher than "theoretical vacuum");

In practice, the absolute pressure of vacuum pump is between 0 ~ 10 1.325 kPa. The absolute pressure value needs to be measured by an absolute pressure gauge. Under the conditions of 20℃ and altitude = 0, the initial value of the instrument (absolute vacuum gauge) used to measure the vacuum degree is 10 1.325KPa (i.e. a standard atmospheric pressure).

The second is to distinguish between "relative pressure" and "relative vacuum" (that is, how much pressure is lower than "atmospheric pressure").

Relative vacuum refers to the difference between the pressure of the measured object and the atmospheric pressure of the measuring place. Measure with a common vacuum gauge. In the absence of vacuum (that is, under normal pressure), the initial value of the table is 0. When vacuum is measured, its value is between 0 and-10 1.325 kPa (generally expressed as a negative number).

Question 9: What is vacuum degree? Automobile engine test and inspection;

1. Start test: In order to make the test results accurate, it is necessary to keep the engine at a high temperature. If the engine can't run because of a fault, it can also be measured when the car is cold, but the accuracy will be reduced. When measuring, close the throttle, cut off the ignition system, connect the vacuum gauge to the intake manifold behind the throttle, and start the engine. Observe that the vacuum gauge value should be between 1 1 and 2 1 kPa. If it is lower than 10 kPa, the possible reasons are: low engine speed (weak starter), worn piston ring (loose seal), stuck throttle or stuck throttle.

2. Idle speed test: When the engine with good performance runs at idle speed, the vacuum gauge value should be stable between 60 and 60~70 kPa. Low and stable vacuum If the vacuum reading is below normal and stable, the possible reasons are as follows. Ignition timing is delayed, valve timing is delayed (timing belt or timing chain is too loose), and camshaft lift is insufficient. If the vacuum gauge drops from the normal value and returns at idle speed, the swing vacuum will swing back and forth rhythmically. The possible reasons are: individual valve hairpin or a camshaft is seriously worn, such as the vacuum gauge swinging between 52 and 52~67 kPa, and the possible reasons are: the valve spring is not hard enough. If the vacuum gauge swings back and forth between 38 ~ 6 1 kPa, the reasons are usually: air leakage of the valve, damage of the cylinder gasket, damage of the piston and strain of the cylinder tube.

The above values are for reference only, because the vacuum degree of the engine will change with the altitude and air density, and the standard value of each engine will be different, and the vacuum degree will also change under different working conditions. Therefore, before fault analysis, we should refer to the normal values of the same type of engine for comparison and comprehensive analysis.

Question 10: How to calculate the vacuum degree? There are usually two ways to identify the degree of vacuum. One is to identify the vacuum degree by absolute pressure, and the other is to identify the vacuum degree by relative pressure.

The so-called absolute pressure means that the vacuum pump is connected to the detection container, and the pressure in the container will not continue to drop and maintain a certain value after a long time of continuous vacuum pumping, so the gas pressure in the container is the absolute pressure of the pump. There is absolutely no gas in the fruit container, so the absolute pressure is zero, which is a theoretical vacuum state. In practice, the absolute pressure of vacuum pump is between 0 ~ 10 1.325 kPa. The absolute pressure value needs to be measured by an absolute pressure meter. At 20℃ and altitude = 0, the initial value of the instrument is 10 1.325KPa. In short, the air pressure marked in the theoretical vacuum is called "absolute pressure" or "absolute vacuum".

Relative vacuum refers to the difference between the pressure of the measured object and the atmospheric pressure of the measuring place. Measure with a common vacuum gauge. In the absence of vacuum, the initial value of the table is 0. When vacuum is measured, its value is between 0 and-10 1.325 kPa (generally expressed as a negative number). For example, if the measured value is -30KPa, it means that the pump can be pumped to a vacuum state that is 30KPa lower than the atmosphere where it is measured. The relative pressure measured by the same pump in different places may be different, because the atmospheric pressure measured in different places is different, which is caused by different objective conditions such as altitude and temperature. In short, the atmospheric pressure marked by "the atmospheric pressure at the measuring place" is called "relative pressure" or "relative vacuum".

Absolute pressure is the most commonly used and scientific method in the international vacuum industry. Because the method of measuring relative vacuum is simple, the measuring instruments are common, easy to buy and cheap, so it is widely used. Of course, in theory, the two can be converted to each other. The conversion method is as follows: absolute pressure = absolute value of air pressure-relative pressure at the measurement place.