Vacuum Gauges — Types And Applications

Vacuum technology has a broad range of industrial applications, from manufacturing to automotive engineering. Technicians rely on vacuuming technology to move materials from one location to another and remove pollutants in construction sites. Read on to discover all you need to know about vacuum gauges, from common terminologies, how the systems work to the different types of gauges and their industrial applications.

Understanding vacuum terminologies

Atmospheric pressure — Psi and bars are the most common calibrations for measuring pressure. Atmospheric pressure refers to the pressure prevailing at sea level.

Vacuum pressure — commonly abbreviated as (Pvac), assumes a negative value compared to atmospheric pressure.

Vacuum pressure gauge — refers to the instruments technicians use to measure vacuum, which is any pressure rating below zero. These instruments work hand in hand with vacuum sensors to monitor and alter the level of sub-atmospheric pressure in industrial systems and chambers.

Criteria for selecting vacuum pressure gauges

Below are some of the selection criteria that technicians should consider before purchasing pressure gauges and related instruments.

• What pressure ranges do you intend to detect? Vacuum gauges fall into three different categories depending on the working pressure. These include absolute pressure gauges, medium vacuum, and high vacuum gauges.
• What is the desired range of accuracy you expect from your vacuum instrument?
• What type of gas are you handling? Is it inert gas, corrosive or reactive gases?
• Measuring aside, will you need to regulate and monitor pressure levels?
• What kind of environment do you intend to use your gauges, and what are your power requirements?

Answering the above questions ensures you have the right equipment for the job at hand.

Types of vacuum pressure gauges

There are many varieties of pressure gauges, each having a specific function. However, we can group them into three major categories, mechanical, ionization, and thermal conductivity gauges.

Mechanical gauges

These are gauges that rely on mechanical alteration of tubes or diaphragms to measure and vacuum pressure. Generally, the pressure readings of mechanical pressure gauges are independent of the gas type. Gauges that fall under the automated classification include bourdon gauges, capacitance gauges, diaphragm gauges, and capsule gauges.

Bourdon gauges

The key feature of these gauges is a tube bent into a circular arc, with its end attached to the vacuum system. External atmospheric pressure causes bending of the end tube during the evacuation process. The bending of the end tube causes movement of the pointer attachment a technician to note the pressure levels on the linear scale. Most bourdon gauges can measure pressure levels ranging between 0 bar, the atmospheric pressure, and ten mbar.

Capacitance gauges

The main feature of these gauges is a pressure-sensitive diaphragm made from reinforced ceramics. The diaphragm has an electrode attachment fixed on the rear side together with a plate capacitor. A variation in capacitance occurs when the two capacitor plates move away or towards one another. The change in the distance of the plates is usually proportional to the pressure variation. The gauge converts this pressure variation into an electrical signal allowing the technician to measure pressure levels accurately. Capacitance gauges can measure pressure levels ranging from 10 bar to readings well above 0 bar.

Diaphragm pressure gauges

The highlight feature of these gauges is a diaphragm that separates the sealed and evacuated vacuum compartment from the vacuum pressure. As the evacuation increases, the variation between the pressure in the vacuum chamber and the pressure to be measured decreases, thus leading to flexing of the diaphragm. The degree of flexing by the diaphragm is then relayed to a pointer scale via a mechanical lever or electrically through a bending bar or strain gauge into an electrical signal. Diaphragm gauges can measure pressure levels ranging from 1 bar to over 1500 bar.

Capsule gauge

Like their diaphragm counterparts, these gauges spot a sealed and evacuated, thin-walled capsule housed within the measuring instrument. The capsule expands when the vacuum pressure decreases. The movement of the capsule is relayed to a pointer scale through a network of levers allowing the engineer to read the pressure level from the linear scale.

Thermal conductivity gauges

Also referred to as Pirani, these gauges rely on the principle of thermal conductivity of gases to measure pressure levels ranging from 0 bars to 10-4 Torr. An electrical current heats a tungsten wire which then cools as gas molecules react with the wire. Pressure build-up in the vacuum chamber leads to more gas molecules colliding with the tungsten wire leading to heat loss. Low-pressure levels translate to a reduced collision of gas molecules with the tungsten wire. The thermal conductivity of the tungsten wire varies depending on the type of gas in the chamber. The change in resistance of the tungsten caused by temperature variations is then converted into a pressure reading.

Ionization gauges

Ionization gauges fall into two major categories; hot and cold cathode gauges. Hot cathode gauges work by emitting electrons and ionizing the gas and pressure the technician intends to measure. Engineers can deduce the gas pressure by measuring the flow of electric current between the anodes and the glass bulb within the cathode. However, hot cathode gauges with high-temperature variations are prone to error which is not the case with cold cathode gauges.

Applications of vacuum pressure gauges

Pressure gauges have a broad range of industrial applications spanning research and development to nautical and manufacturing. More importantly, gauge sensors are used in manufacturing to ensure the proper functioning of equipment to guarantee worker safety.

Pharmaceutical, paper milling, and offshore oil drilling companies are other sectors that heavily rely on vacuum technologies for their day-to-day operations. Petroleum refineries and chemical plants use vacuum pressure gauges to move gas and liquid materials through their systems. Site workers rely on pressure instruments to remove pollutants from working sites.

High Vac Depot offers efficient vacuum solutions that meet industrial and research needs. Get in touch with us today!