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Absolute pressure = gauge pressure + atmospheric pressure

When using a pressure gauge, like when measuring the pressure of the air in a tire, the gauge is actually reading the difference between the atmospheric pressure and the atmospheric pressure. So if the gauge measures 30 psi, and taking atmospheric pressure at about 14.7 psi, the absolute pressure in the tire is actually about 44.7 psi. If the tire is flat, then the gauge will read zero psi, but there is not a vacuum - there is still some air present in the tire, and the absolute pressure of this air is the same as the atmospheric pressure (about 14.7 psi).

See related link: Guide to the Measurement of Pressure and Vacuum.

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13y ago
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8y ago

Humidity is the actual amount of moisture in a certain volume of air.

Relative humidity is the percentage of the maximum amount of moisture that's possible in certain volume of air for a particular temperature.

Example of Relative Humidity: Suppose a 5 ft. cube of air could could hold a maximum 10 oz. of moisture at 80 degrees. Now suppose that the cube of air actually contains 5 oz. of moisture. The Relative Humidity would be 50%.

The idea of humidity refers to how much water is mixed in with the air around us. Everywhere on Earth there is always at least some water mixed in with the air; in some places, like the desert, it's just a little; in other place, like by the ocean or in a rainforest, it's a lot.

The air can only carry around a limited amount of water vapor (evaporated water, or water in its gas form). At some point, there can be more water vapor than the air can hold, and the water turns into little droplets, which in nature is clouds, fog, or rain.

Just "humidity," also known as "absolute humidity," means "what is the concentration of water vapor (evaporated water) in the air right now?" In other words, it would give you a measurement of how much water you would get if you could take a box of air and squeeze all the water out.

This is expressed in units of mass/volume. So, for example, you could express the absolute humidity as 5 grams per liter (5 g/L) if there were 5 grams of water vapor floating around in every liter of air.

Again, the air can only carry around a limited amount of water vapor. How much it can carry is determined by the atmospheric pressure and the temperature. There is a mathematical equation that lets you figure out the maximum amount of water that the air can carry based on the pressure and temperature. Relative humidity is how much water the air is actually carrying divided by how much water the air could possibly carry. People, especially weather forecasters, usually express this as a percentage. So, if the air in a particular place is carrying exactly half the amount of water that it could theoretically carry, the relative humidity would be 50%. If it were carrying all the water it could theoretically carry, the relative humidity would be 100%. The relative humidity can never be higher than 100% or lower than 0%.

Relative humidity has no units, because it is just a fraction.

So, ways they are alike:

1. They both talk about how much water vapor is mixed with air in a particular place.

Ways they are different:

1. Humidity has units (mass/volume) but relative humidity is just a fraction or percentage.

2. Humidity doesn't care about how much water vapor it's possible for the air to have, but relative humidity does.

3. Humidity doesn't tell you anything about how close the air is to having rain or fog, but relative humidity does.

Specific humidty is the amount of water in unit amount of air by weight

and

Relative humidity is the amount of water in unit amount of air by pressure(partial pressure)
Relative humidity is one means of describing the amount of water in the air. Relative humidity describes the amount of water in the air as that precentage of the total amount air at that temperature should be able to hold.

Absolute humidity describes the amount of water in the air by saying how many grams of water per milliliter of air are present.

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7mo ago

Gauge pressure measures pressure relative to atmospheric pressure, while absolute pressure measures pressure relative to a perfect vacuum (zero pressure). Gauge pressure will read zero when the pressure is at atmospheric level, while absolute pressure will read zero only in a perfect vacuum.

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15y ago

Absolute air pressure provides the display of the true measured air pressure of the current time and location. Relative air pressure is the one value that is calculated back to sea level from the local absolute air pressure and can thus be taken as a reference for weather condition and weather development for the entire country

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10y ago

Pressure can be defines as a force acting normally on unit area of the surface. also mathematically pressure can be defined as : pressure= normal force/ area Atmospheric pressure decreases with altitude and is measured by barometer.

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12y ago

what is absolute pressure? what is difference between absolute and deferential pressuer in term of aviation.

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11y ago

There are many differences between gauge pressure and absolute pressure. Gauge pressure is measured from atmospheric and absolute pressure is measured from zero.

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6y ago

The gauge pressure is the difference between absolute pressure and atmospheric pressure.

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13y ago

absolute pressure is 0.

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Q: What is the difference between gauge pressure and absolute pressure?
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If the absolute pressure of gas is 550.280 kPa it's gage pressure is?

The gauge pressure is the difference between the absolute pressure and atmospheric pressure. If atmospheric pressure is approximately 101.3 kPa, then the gauge pressure would be 448.980 kPa (550.280 kPa - 101.3 kPa).


How do you find gage pressure?

Gauge pressure is calculated by subtracting the atmospheric pressure from the absolute pressure. It is important to note that gauge pressure readings are relative to atmospheric pressure. So, to find gauge pressure, you would subtract the atmospheric pressure from the total pressure reading obtained.


What are the difference between room pressure and absolete pressure?

Room pressure refers to the pressure within a confined space like a room, which may be controlled to prevent contamination or maintain a sterile environment. Absolute pressure, on the other hand, refers to the total pressure within a system including both atmospheric pressure and any additional pressure exerted.


If a gas has a gage pressure of 206 kPa its absolute pressure is?

The absolute pressure can be calculated by adding the atmospheric pressure to the gauge pressure. If the atmospheric pressure is 101.3 kPa, then the absolute pressure of the gas would be 206 kPa + 101.3 kPa = 307.3 kPa.


Why does an air gauge that is connected to water read 3x the pressure that the water gauge read?

An air gauge measures pressure relative to the atmospheric pressure, while a water gauge measures pressure relative to its own density. Water is denser than air, so the air gauge reading will be 3 times higher than the water gauge due to the difference in reference points for each gauge.

Related questions

What are you measuring when you measure air preasure?

The difference in pressure between absolute and gauge pressure.


What is the difference between normal pressure gauge and differential pressure gauge?

A pressure gauge indicates actual pressure and a differential pressure gauge indicates the difference in pressure.


If the absolute pressure of gas is 550.280 kPa it's gage pressure is?

The gauge pressure is the difference between the absolute pressure and atmospheric pressure. If atmospheric pressure is approximately 101.3 kPa, then the gauge pressure would be 448.980 kPa (550.280 kPa - 101.3 kPa).


How do you find gage pressure?

Gauge pressure is calculated by subtracting the atmospheric pressure from the absolute pressure. It is important to note that gauge pressure readings are relative to atmospheric pressure. So, to find gauge pressure, you would subtract the atmospheric pressure from the total pressure reading obtained.


Is PSI absolute or gauge pressure?

gauge


What is the definition of psia and psig in pressure unit?

PSIA stands for pounds per square inch absolute, which measures pressure relative to a perfect vacuum. PSIG stands for pounds per square inch gauge, which measures pressure relative to atmospheric pressure.


Gauge pressure and absolute pressure?

Gauge pressure is what you get when you take the reading from your tire pressure gauge. Absolute pressure is the pressure inside your tires plus the atmospheric pressure, which is roughly; 14.7 psi, 101.3 kPa (kilo-Pascals), or one atmosphere. Absolute pressure measures all of the pressure on your tires, inside and out, whereas gauge simply measures the pressure inside the tire.


What does a compound pressure gauge measure?

i need to explain what an absolute pressure gauge measures


If a gas has an absolute pressure of 319 kPa its gage pressure is?

The gauge pressure is the absolute pressure minus atmospheric pressure. If atmospheric pressure is considered to be 101 kPa, then the gauge pressure would be 219 kPa.


Is gauge pressure is the sum of true pressure and atmospheric pressure?

No, it is the DIFFERENCE between the true and atmospheric pressures.


What are different types of pressure sensors?

absolute pressure; gauge pressure; atmospheric pressure...


If a gas has a gage pressure of 206 kpa its absolute pressure is approximatly?

if the gauge pressure is 206 kPa, absolute pressure is 307 kPa