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Flowmeters: Introduction

Flowmeters or flow sensors can be defined as devices that can help to measure the flow rate of a substance. In other words, such instruments show how much liquid or gas is flowing through pipelines or other enclosed systems and at what rate.

Interestingly, the necessity of measuring airflow and water distribution was eminent in the ancient world, as early as 5,000 BC, especially for navigating, water supply, and agriculture. Yet, it was in 1908 when the German engineer Karl Kueppers developed the first true variable area (VA) flowmeter with a rotating float, also called rotameter. Meanwhile, the first glass rotameters were manufactured in the UK. Note that as of 2016, the Japanese company Yokogawa Electric Corporation holds the patent for the rotameter. Flowmeters, originally designed to measure liquids, evolved over the years (particularly in the 50s) and started being utilized in gas and steam flow measurements.

From positive displacement flowmeters and Coriolis units to Vortex meters and turbine models, now different types of flowmeters can be used in different specialized areas, such as manufacturing settings, households, health research, municipality systems, and mining. Also, flowmeters can be used for energy saving to measure different fluids, including oil. Note that some modern equipment can connect to computer software to monitor changes over time and detect errors.


How to Choose a Flowmeter

Choosing a flowmeter can be a challenging task, especially for non-specialists and do-it-yourself enthusiasts. Prospective buyers should consider various aspects, such as the fluid being measured, its viscosity, and the size of the piping system; users should also decide if they need a local display or a digital output of the collected data. To be more precise, the three main areas buyers should assess are:

  • Requirements
  • Specifications
  • Total costs

Requirements: The first aspect to consider is the fluid being measured (e.g., water, gas, oil). The fluid’s characteristics should be taken into accounts, such as pressure, temperature, density, composition, conductivity, toxicity, light transmission, and viscosity (of both Newtonian and non-Newtonian fluids). Another important factor is the piping system and its interaction with the fluid of interest. Based on their requirements, users can choose from paddle wheel, piston, thermal, oscillatory, electromagnetic, Karman vortex, ultrasonic, positive displacement, and other flowmeters. Note that variable area flowmeters are among the most common type of meters used today. Last but not least, prospective buyers should decide if the information (continuous or totalized) will be used locally or remotely, including digitally.

Specifications: One of the leading parameters to consider is a unit’s Reynold’s number. We should mention that this number should correspond to different fluids and their viscosity levels. Users should also choose appropriate measurement ranges; note that the turndown indication on any flowmeter should show the lowest and the highest numbers it can support. Additionally, choosing a flowmeter should be based on its accuracy. Interestingly, when it comes to meters with and without moving parts, flowmeters without moving parts are preferred as additional fragments may lead to wearing and inaccurate readings.

Total costs: Deciding on a budget is vital. While it’s true that inexpensive units might be inferior in design and performance, it is noteworthy to mention that measuring water and airflow at home does not always require specialized equipment; nevertheless, some cheap units may come with high installation costs and risks. Note that in case users need to know the rate at which a fluid is moving – not to control it – they can invest in simple flow indicators instead.


Variable Area Flowmeters in Detail

Variable area flowmeters, as stated earlier, are some of the most common meters for sale. They are ideal for low-cost solutions and can be used to determine flow/no-flow indications. Purgemeters, on the other hand, are ideal for low-flow settings. Note that VA units vary according to their float shape and material; there are plastic, glass, and metal models that can be used for different fluids and applications.

Here we should mention that some of the leading manufacturers are KROHNE (ideal for chemical processes and wastewater settings), Blue-White Industries (offering acrylic and polysulfone VA meters, as well as tube and block units), Brooks Instruments (producing units ideal for low and high-flow measurements, as well as MT Series models for aggressive fluids), and Yokogawa (offering different transmitter outputs).


Best Flowmeters for Sale

Interestingly, while VA flowmeters are affordable and convenient, turbine and positive displacement meters have expanded their market size significantly. Based on different parameters and user reviews, here are some of the best flowmeters available on the market:

Blue-White Flowmeter for 2″ PVC Pipe – Horizontal Installation

It is a durable flowmeter suitable for both home use and commercial applications. Note that the unit is designed to measure horizontal water flow, with an easy-to-read dual scale (SCH 40/SCH 80). With its convenient Pilot Tube design, this meter is easy to install on an existing piping system (suitable for PVC and copper pipes); the set comes with a gasket seal and mounting clamps. Last but not least, it is worth noting that this one-piece acrylic meter body is suited for closed pipe installations, as well as outdoor installations.

Ameriflame RF2480-320 CO2 Flowmeter Regulator with Single Stage CGA320 Inlet

It is a great meter designed to measure gas flow. Moreover, the unit can be used as a regulator and a flowmeter at the same time (4000 psi/kg/cm2). Note that this meter is calibrated for argon and CO2and its hose nipple fits both ¼-inch and 3/16-inch systems, which also makes it ideal for regulating shielding gas during metal inert gas (MIG) and tungsten inert gas (TIG) welding. With its solid brass body, easy-to-read 1.5-inch gauge, and rubber gauge protector, Ameriflame RF2480-320 is a highly favored flowmeter.

Fill-Rite 820 1″ 2-20 GPM(8-76 LPM) Digital Nutating Disc Fuel Transfer Meter

It is an advanced digital meter designed for water, diesel, and mild chemicals (2 to 20 GPM at pressures up to 125 psi). Its digital display is easy to read, so users can take accurate readings (with +/-2% accuracy). Moreover, users can obtain data in different units, such as ounces, pints, liters, and gallons, without the need for conversions. With its polypropylene body, stainless steel construction, and FKM seals, the unit is also suitable for outdoor use. Note that the display is powered by two AA batteries (included).

SPARC Dual Output Argon Regulator Flowmeter Mig Tig 0-60CFH CGA580 Inlet 5/”8 Outlet

It is a versatile flowmeter ideal for MIG and TIG welding. With its CGA580 bottle inlet connection, the unit fits standard argon, helium, nitrogen, argon, and CO2 style gas bottles. Note that the output flow can be adjusted from 10 to 60 ft3/h at a preset 50 psi, while the pressure gauge can show how much is left in the tank (from 0 to 4000 psi). Moreover, the set comes with adapter fittings.

Philips Respironics Hs755 Personal Flow Meter

It is a great peak flow testing unit, often considered the most advanced peak flow meter available. The unit is ideal for people with asthma and other health conditions who wish to track their airflow. The unit is safe for oral use, easy to clean, and read. To be more precise, this meter has a built-in flexible three-zone management system with color-coded indicators that can determine a patient’s green, yellow, and red zones based on their personal best peak flow; available in full (60-810 l/min) and low (50-390 l/min) ranges. With a handle that converts into a protective case, this meter is also portable and durable. Note that the unit is available only with a business account and a healthcare license.


Flowmeters: Installation, Maintenance, and Safety Tips


  • Always consult the instruction manual before installation and use.
  • One of the most important factors to guarantee accurate readings and long life is to choose a meter that matches the particular application.
  • Another major factor is the complexity of installation. Note that units should be installed where few obstructions (e.g., bends) exist. Specialized assistance may be required.
  • Flowmeters without any moving parts are easier to maintain compared to units that consist of moving fragments.
  • When it comes to peak flow meters, if readings are in the red zone (under 50% of one’s personal best reading), medical attention should be sought as shortness of breath, wheezing, and chest tightness can get out of control.


Flowmeters: Conclusion

Flowmeters have become invaluable devices that can help to measure the flow rate of water, gas, air, and other substances. Due to the variety of units for sale, such as VA models, Coriolis meters, and positive displacement flowmeters, prospective buyers should consider three major factors: requirements, specifications, and total costs. Most of all, users should assess the fluid of interest and its characteristics (e.g., pressure, viscosity, temperature), so that meters can match the particular application.

From engineering to research, flowmeters can be applied to numerous areas, including health settings and environmental control. With their vast applications and versatile designs, flowmeters are among the most in-demand meters used by both specialists and do-it-yourself enthusiasts.