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Air Flow Meters

What is an "air flow meter"?

Let’s start by acknowledging that the specific term “air flow meter” and other similar terms can mean vastly different things to different industries. Here is some helpful clarification regarding the items that “air flow meter” could be referring to.

What is an Air Flow Meter

What is a mass air flow sensor in the automotive industry?

In the industrial instrumentation world, the term flow meter and flow sensor are sometimes used interchangeably as a flow meter is technically a type of flow sensor.

However, in the automotive industry a “mass air flow sensor” is a car part that is integral to the fuel injection system and measures the air flow into the engine. Without proper flow, your car can experience significant performance issues and the dreaded “check engine” light. While a “mass air flow sensor” does measure flow, they are not used for any other applications besides the automotive industry.

What is an anemometer or air flow meter for HVAC applications?

In the HVAC field, especially for commercial and industrial use buildings, there are many systems that require measuring and monitoring the flow of air. Typically, “air flow meters” for HVAC applications measure the air velocity though the piping or duct work. The instrumentation that typically performs this task are usually referred to as anemometers.

Anemometers themselves can come in many shapes and sizes and are used in different application fields. In measuring the wind speed of outdoor weather, common anemometers are rotating vanes with cups at the end of arms that are pushed by the movement of the wind. The speed of the rotation of the main rod is converted into a wind speed measurement. Anemometers can also look like little mini fans contained in housings, which again are rotated by the movement of air passing through the blades.

Anemometers can also feature no moving parts, like our KAH low velocity anemometer air sensor. Built on a hot-film principle, these anemometers use the cooling effect of the air passing a heated element, like the probe of the KAH. The faster the air speed, the more the probe is cooled, and this can be turned into an air velocity reading. Visit our article on thermal dispersion flow to learn more about how this technology works.

Because thermal dispersion flow technology does not contain moving parts, it can deliver a very long service life compared to other anemometer types that are subject to mechanical wear and tear.

Other common flow instrumentation for HVAC applications include air flow switches, like our LSP Air Flow Switch for HVAC Ducts which feature an adjustable switch point and are designed for square/rectangular horizontal HVAC ducts.

What are industrial air flow meters?

This category of “air flow meters” refers to industrial flow meters that measure the flow of air through a pipe within a process or a system. Most of these industrial air flow meters can also handle certain other gas types as well.

Many industrial flow meters also offer switching capabilities so a process can be shut down or an alarm can be triggered when a certain flow is exceeded. If continuous air flow measurement is not needed, then a simple flow switch is a much more cost-effective option.

There are many common industrial applications that require the monitoring and measurement of air. A common one is the field of pneumatics, where air is used to create force to deliver mechanical energy to a movement or a process. Visit our article to learn more about pneumatics and hydraulics in the field of fluid power.

Examples of other common industrial applications include power tools, combustion furnaces and boilers, gas mixing, and wastewater aeration.

What are the types of air flow meters?

Not all flow meter technology types are compatible with air. Some flow meter technology types are only suitable for liquids. The most common flow meter technologies used for measuring air and other gas types are:

  • Rotameters/Variable Area Flow Meters
  • Vortex Flow Meters
  • Thermal Mass Flow Meters
  • Some Differential Pressure Flow Meters
  • Coriolis Flow Meters
  • Oscillation Flow Meters
Air Flow Meter Types

What is the most accurate air flow meter?

While there are many types of specific flow meter technologies, they can also be classified into two categories. Ones that do not utilize any moving parts in the principle of operation, and ones that do. Generally speaking (and excluding DP Meters), technologies that do not include mechanical elements will be more accurate than technologies that do. Coriolis flow meters are usually the most accurate option available for air, however they are also usually the most expensive option out there and are overkill if it is not a highly specialized application.

Here are some sample accuracies:

What units of measurement are there for industrial air flow meters?

The typical US units of measurement for air flow are standard cubic feet per minute (SCFM) or standard cubic feet per hour (SCFH). These are both volumetric units of measurement describing how much air is moving through the pipe in reference to a unit of time, as opposed to a velocity measurement like an anemometer which states the speed at which the air is moving.

KOBOLD offers a very wide variety of air flow meters in SCFM. For simple air flow measurement, visit our selection of rotameters. Most of them offer direct-reading air measurement in SCFM.

How do air flow meters work?

Industrial air flow meters work according to their specific technological principle of operation.

Rotameter air flow meters

Rotameters, also known as variable area flow meters, are typically a tubular flow body with a float. When air flows, the float moves up in the tube and the flow can be read by referencing the top of the float against the scale printed on the tube. These typically also provide visual flow indication through transparent flow bodies. To learn more, visit our article on rotameters/variable area flow meters.

Vortex air flow meters

Vortex flow meters operate by placing a small obstruction (known as a bluff body) in the path of flow. A series of “eddies” is created behind it. These vortices alternate side to side and the shift in pressure is processed into a flow rate. To learn more, visit our article on vortex flow meters.

Thermal dispersion air flow meters

Thermal flow meters employ a heated element, such as a probe, into the flow path. As the air passes, the heat of the probe is dissipated and the probe cools. The amount of cooling that occurs can be computed into a flow rate. To learn more, visit our article on thermal flow.

Differential pressure air flow meters

Differential pressure flow meters typically use an orifice plate, or some other change in shape, within the flow that generates a difference in pressure before and after the element. This difference is then processed into a flow rate.

Coriolis air flow meters

Coriolis flow meter operation is more difficult to summarize. To learn more about the Coriolis flow meters, visit our in-depth Coriolis flow meter article.

Do flow meters for air offer digital displays?

Not all air flow meter technologies deliver digital capabilities. Variable area flow meters do not typically provide digital displays.

Of the other air flow meter technology types, most of them have digital capabilities. Here are some examples:

Digital Air Flow Meters <

How do you check air flow in a pipe?

If you simply need to verify that air flow is occurring in a closed pipe system, your application probably only requires a simple flow indicator and not a flow meter. If you need to know exactly how much air is flowing through the pipe at any given time, then you will need a flow meter.

How to Check Air Flow in a Pipe

How do you choose a flow meter for air?

Choosing the right flow meter to monitor or measure your air flow can seem like an intimidating prospect.

In general, here are some basic things to keep in mind while looking for an air flow meter.

  • The type of air - Not all air is created equal. Some of it can be considered clean and some of it is dirty. Is the air dry or humid? Humid air requires special consideration. Our DOG Oscillation Flow Meter offers a unique design that drains condensate build-up from humid air.

  • The total range of possible flow rates - What will the maximum flow rate be and what will the minimum flow rate be? Flow meter have minimum and maximum flow rates.

  • The maximum temperature - Depending on their material of construction, flow meters can only handle a certain maximum temperature without risking damage to the instrument.

  • The maximum pressure - Certain build materials are only suitable for lower pressures. High pressure applications will typically require a metallic build and specialized glass.

  • The line size and connection - Not all flow meter models come in all line sizes. Also consider what connection type will most easily incorporate the meter into the application.

  • Insertion or inline installation - If you prefer to not cut into your pipes, creating downtime and revenue loss, consider an insertion air flow meter.

  • The accuracy - Determine what level of accuracy your application requires. High accuracy generally requires more expensive flow technology that does not include any moving parts. Many applications really do not require the level of accuracy to justify the higher cost over a mechanical flow meter like a rotameter.
How to Choose an Air Flow Meter

What is an inline air flow meter?

An inline air flow meter is simply an air flow meter that is intalled inline with the process piping. There is an inlet and an outlet and the flow passes through the flow body that is placed into the pipe via fittings like NPT or ANSI flanges.

Inline Air Flow Meters

What types of flow meters handle compressed air?

Industrial air flow meters may need to measure pressurized air that is higher than normal atmospheric pressure.

A simple example of compressed air is a can of pressurized air used to clean sensitive computer parts. A common compressed air application is pneumatic systems where pressure is required to create the force for movement.

Flow meters for compressed air need to be able to handle higher pressures than standard air applications. For this reason, most compressed air flow meters are built of a more rugged material like metal.

Compressed Air Flow Meters

How much do air flow meters cost?

The price of an air flow meter can vary extensively and is primarily dependent on your choice of flow meter technology, your line size, and the features the air flow meter needs for your specific application.

Among the typical air flow meter technology choices (rotameters/variable area, vortex, thermal mass, differential pressure, oscillation, and Coriolis) rotameters are generally going to be the cheapest for any simple application. However, they do not typically offer functions like totalizing or batching.

Coriolis flow meters are generally the most expensive type of flow meter that can measure air. They are typically required for more specialized applications with more demanding process conditions.

Vortex flow meters, differential pressure flow meters, and thermal mass flow meters can all vary in price per model, but in general, they fall in the middle cost-wise.

Air flow meter suppliers and manufacturers

KOBOLD and its subsidiaries have been manufacturing air flow meters for decades and bring a wealth of experience and expert advice to your specific application needs. We not only manufacture air flow meters, but we also sell and support them as well, providing the total customer experience in one place for the life of your air flow meter.

KOBOLD offers one of the largest rotameter lines in the industry and many other air flow technologies like differential pressure, thermal mass, vortex, oscillation and Coriolis. Contact us today at info@koboldusa.com or 412-788-2830 and make use of our free and personal approach to flow meter selection.

Help Selecting a Flow Meter
Featured Products
BGN
Heavy-Duty Industrial All-Metal Variable Area Flow Meter
BGN - All-Metal Armored Flow Meters

Liquid, Gas, or Steam | Direct Reading Scales | Up to 550 GPM or 640 SCFM | Up to 660 °F | Up to 8,700 PSI | NPT or ANSI Connections | Variety of Material Options

KSM
All Plastic Flow Meter and Switch
KSM - All-Plastic Flow Meter and Switch for Liquids or Gases

Made in the USA | For Liquids | Direct Reading Scales for Water or Air | Large, Easy to Read Scale | Shock and Corrosion Resistant | Up to 260 GPM or 400 SCFM | Up to 145 PSI

RCM
Orifice Type Differential Pressure Flow Meter
RCM - Differential Pressure Orifice Flow Meter - High Flow Rates

Digital or Mechanical Displays | Liquid, Gas, or Steam | High Rangeability | Up to 3,000 GPM or 20,000 CFM | Up to 400 PSI | Up to 350 °F | Optional Alarms and Output Signals

About KOBOLD

KOBOLD USA is a subsidiary of KOBOLD Messring GmbH, a world-leading instrumentation engineering business founded in Germany in 1980 by Klaus J. Kobold. With patented technology and superior service, the company quickly established itself as one of the global leaders in sensor and control systems with high quality products. The KOBOLD brand name became synonymous with superior quality and technological advancement in instrumentation engineering.

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