Pressure measurement is a crucial factor when it comes to determining the force applied to a surface either by a solid, liquid, or gaseous material. Using a vacuum gauge, the pressure is typically measured in units per surface area of the said surface where a force is exerted upon.

Over the years many techniques have been developed to help measure pressure and vacuum. Instruments used to measure and display pressure in an integral unit are called pressure meters or pressure gauges, or vacuum gauges.

An example of an instrument used in measuring pressure is the manometer and the Bourdon gauge. Both of which measure pressure using surface area and weight.

Vacuum gauge

The vacuum gauge is a device for measuring pressures below atmospheric pressure in the receiver of an air pump. Also in steam condensers, and the like. It can also be interpreted as a pressure gauge used to measure pressures lower than the ambient atmospheric pressure. This type of pressure is set as the zero points, in negative values [-760mmHg].

How does a vacuum gauge work?

In cars

An automotive vacuum gauge can be an important automotive tool for car owners. Because can be used to get specific readings on the air pressure in their engine. This device is a reliable tool to sustain the quality of this critical feature of your vehicle. The amount of airflow allowed by the throttle into the intake manifold generates power to the engine.

To diagnose the vacuum systems in your car, you make use of an automotive vacuum gauge. It is the most powerful method available to ensure that air leaks are not encountered by your engine. These air leaks could lead to rough idling, low fuel efficiency, and increased emissions.

Another type of gauge present in cars is the fuel gauge, you can find out more about it in this article. Also, we have the fuel pressure regulator that ensures the engine gets the right amount of fuel every time.

Types of vacuum gauge

These devices can be classified into two groups.

Vacuum gauges whose pressure readings are independent of the type of gas (Mechanical Vacuum Gauges).

Examples include capsule vacuum gauge, bourdon vacuum gauge, diaphragm vacuum gauge, capacitance vacuum gauge.

Vacuum gauges whose pressure readings depend on the type of gas.

Examples include thermal conductivity gauge, cold cathode ionization vacuum gauge, hot cathode ionization vacuum gauge.

Vacuum gauge versus pressure gauge

A pressure gauge measures the pressure of a liquid or gas. Atmospheric pressure is usually taken as a reference for most measurements. Without going into details, approximately 760 mm Hg column supported by the atmosphere at standard conditions is taken as 1-atmosphere pressure.

A pressure gauge can only measure in positives so any measurement from zero to 760mm Hg is considered pressure. Meanwhile, anything from zero to -760mmHg is termed a vacuum.

Pressure measurement is done by various methods and different types of pressure gauges. Atmospheric pressure is usually taken as a reference for most measurements. Any pressure above this is positive pressure and the one below this is negative pressure or vacuum.

Vacuum gauges start at zero and go up to -760 mm Hg. You need high precision electronic gauges for a very high vacuum. The pressure is measured in Hg mercury (manometers) for mercury type meters. Some others start below 10 mm or 1 mm. Resolution may vary and go to 0.001mm Hg (Torr) for Mercury type meters.

Uses of a vacuum gauge

A vacuum gauge is known to be a device that helps reading the pressure amount of an engine. Even this device also helps to measure the sub-atmospheric pressure. There are various types of pressure gauges available in the market nowadays. But these vacuum gauges are often used to measure the vacuum of a specified closed space.

Most industries are now choosing the vacuum gauge for their industrial applications and processing. From mining, manufacturing, aeronautics, food processing, to beverage production units, this device is needed. There are hundreds of models available in the market of these vacuum gauges and you need to install the specific one as per your industry type.

Some types of vacuum gauge explained

• U Tube Manometer:-This is the most basic of the various types out there. It is used for measurement using the height of a liquid column of mercury.
• Bourdon Gauge: This gauge uses a curved metal tube that on one side is closed and on the other side is connected to a vacuum.
• Thermocouple Gauge: A thermocouple is a spot welded directly to the heated wire.  This feature differentiates it from the Pirani Gauge. For this type, direct temperature measurement is taken which is transformed into a vacuum measurement.
• Hot Cathode Ionization Gauge: A warm wire is used in this gauge. To generate electrons by thermionic emission. The electrons thus produced are drawn to the anode that is in the form of a grid. The ion current will depend on the vacuum level. Therefore, measuring the current shows the vacuum level and can estimate the vacuum up to 10-3 Torr.
• Penning Gauge: The name of this gauge comes from its inventor. To create a self-sustaining light, a high potential difference is applied. The magnetic field is applied around the glow. The current produced depends on the level of vacuum and thus the glow current measurement indicates the level of vacuum. Up to 10-7 Torr, the gauge can measure vacuum accurately.

How to perform a vacuum test

You need to locate a port in the manifold or throttle body to check manifold pressure with a vacuum gauge. A vacuum test shows the difference between outside atmospheric pressure and the amount of vacuum present in the intake manifold. The amount of vacuum produced is influenced by the piston rings, valves, ignition system, and fuel system.

Each has a characteristic effect on the engine's running and by watching variations from normal, you judge performance/issues. Judging engine performance by the general location and action of the needle on the device is essential.

Key takeaways

• The vacuum gauge is used to measure the ambient pressure in a receiver of an air pump. Also the vacuum in steam condensers.
• You also use it for measuring pressures below atmospheric pressure in general.
• It is very important in engines of vehicles as they help with signaling if a car engine is faulty and requires repairs either major or minor.
• This device is important in various industries so long as they use automotive machines in their production processes.
• Pressure can be measured in a vacuum chamber using various types of vacuum gauging equipment

‍