# Relationship between absolute pressure gauge and vacuum

Absolute pressure is zero-referenced against a perfect vacuum, so it is Differential pressure is the difference in pressure between two points. Difference Between Gauge and Absolute Pressure Measurement pressure is below atmospheric pressure it is called negative or vacuum gauge pressure. Absolute Pressure a perfect vacuum as its reference. Using an absolute pressure sensor eliminates the reference to a varying atmospheric complex than gauge or absolute, but is simply measuring the difference between two medias.

A gauge pressure higher than ambient pressure is referred to as positive pressure. If the measured pressure is below atmospheric pressure it is called negative or vacuum gauge pressure. Gauge pressure sensors only usually have one pressure port. The ambient air pressure is directed through a vent hole or a vent tube to the back of the sensing element.

A vented gauge pressure transmitter allows the outside air pressure to be exposed to the negative side of the pressure sensing diaphragm so that it always measures with reference to the ambient barometric pressure.

Therefore a vented gauge pressure sensor reads zero pressure when the process pressure connection is held open to atmospheric air.

A sealed gauge reference is very similar except that atmospheric pressure is sealed on the negative side of the diaphragm. This is usually adopted on high pressure applications such as measuring hydraulic pressures where atmospheric pressure changes will have only a slight effect on the accuracy of the senso. The definition of sealed-gauge pressure is the pressure measured through a sealed device in which the zero point is set.

This set point is whatever the pressure inside of the device was before sealing, which the manufacturer of the sealed pressure gauge decides.

Absolute Pressure The definition of absolute pressure is the pressure of having no matter inside a space, or a perfect vacuum.

Measurements taken in absolute pressure use this absolute zero as their reference point.

### Difference Between Gauge and Absolute Pressure Measurement

The best example of an absolute referenced pressure is the measurement of barometric pressure. In order to produce an absolute pressure sensor the manufacturer will seal a high vacuum behind the sensing diaphragm.

• Difference Between Gauge pressure and Absolute pressure

To relate information to concepts in a Mechanics of Solids course. To measure both the gage and absolute pressures in a pressurized container balloon. Balloon, ruler, 2 meter length of transparent flexible plastic tubing, support stand and colored water. Inflate balloon to 4 to 5 times its initial deflated diameter.

## Difference Between Gauge and Absolute Pressure Measurement

Configure tubing in a 'U' with about one meter of water at bottom about inches in each leg. Slowly open the balloon to the manometer.

You may need to lower the balloon end somewhat to prevent the water from flowing out the open end. When steady, measure the difference in height DH of the water in the two columns of the tubing. This is a 'U' tube manometer.

### terminology - Gauge pressure vs. absolute pressure? - Physics Stack Exchange

Calculate the pressure difference between the balloon and the atmosphere based on water density, gravity and differential height. This is the gage pressure in the balloon, which is the pressure in the balloon above atmospheric. From your local TV weather station, local airport or an available barometer, determine the local atmospheric barometric pressure.