This article takes an in depth look at mass flow meters and their use.
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A mass flow meter determines the flow rate of gases by assessing heat transfer across the gas's surface, using temperature sensors and electric heaters either within the flow path or externally. On the other hand, inertial flow meters calculate the mass flow rates of fluids as they transit past a fixed point over a given duration.
Mass flow meters are known by various names in different industries, such as flow gauge, flow indicator, liquid meter, and flow rate sensor. They have largely supplanted other flow rate measurement techniques because of their exceptional accuracy and precision.
There are multiple technologies for measuring mass flow, such as Coriolis, inertial, and thermal methods. Coriolis flow meters utilize the Coriolis effect, where a moving mass within a rotating system produces a force that is perpendicular to both its motion and the axis of rotation. These meters detect the inertial forces from gas moving through vibrating tubes and use sensors to measure the oscillations' amplitude, frequency, and phase shifts to evaluate mass flow.
Thermal mass flow meters depend on heat transfer principles, employing a heating element and temperature sensors. As gases move past these sensors, they create thermal energy that increases their temperature, allowing the determination of flow rate.
The above image provides a general view of a mass flow meter installed within a pipe for flow rate measurement.
Manufacturers design mass flow meters with integrated temperature and pressure sensors along with the flow sensor. These meters calculate mass flow using electronics based on the formula: mass flow equals density times the volumetric flow rate, which is then multiplied by the cross-sectional area of the flow path, a constant set by the flow body's size. Density is computed from pressure and temperature readings, while velocity is measured using a rotating turbine or vortex sensor.
Precision in flow measurement is essential for maintaining process conditions in a facility, influencing production effectiveness and product excellence. In some instances, flow measurements also act as indicators of overall process efficiency.
Mass flow meters play a pivotal role in modern industrial processes by delivering precise and reliable flow rate measurements for liquids and gases. Although all mass flow meters are engineered to measure flow rates, each uses a different measurement principle based on the substance in question, site conditions, and the accuracy level required. Common mass flow meter types include Coriolis mass flow meters, thermal mass flow meters, and differential pressure (DP) mass flow meters, each specifically suited to certain applications and media.
In industrial production facilities, accurate flow measurement is essential for process control, resource optimization, and maintaining product quality. Mass flow meters deliver real-time data on fluid or gas flow, supporting key functions like batching, mixing, chemical dosing, and fuel consumption monitoring. By continuously measuring and monitoring flow rates, mass flow meters help maximize efficiency, minimize waste, and ensure compliance with industry standards.
One of the main reasons engineers opt for mass flow meters is their ability to automatically detect variations in media, such as changes in viscosity, density, or temperature, which can dramatically impact volumetric flow meters’ accuracy. Temperature fluctuations, for example, directly affect fluid density, which can introduce significant errors if not accounted for. Mass flow meters excel in applications where accurate, repeatable measurement is critical, such as in petroleum, chemical processing, food and beverage manufacturing, wastewater treatment, pharmaceutical production, and fuel management—especially when tight tolerances (typically within ± 1%) must be maintained.
Below is a brief overview of how the most widely used types of industrial flow meters operate, including their principles of operation, strengths, and primary use cases.
Direct mass flow measurement methods eliminate inaccuracies associated with the fluctuating physical properties of fluids and gases. Unlike volumetric flow meters, direct mass flow meters capture absolute values—enabling accurate mass flow readings regardless of variations in pressure, temperature, viscosity, or media density. This capability makes mass flow meters highly desirable for process-critical operations in industries such as oil & gas, food processing, pharmaceuticals, and chemical manufacturing.
Volumetric measurement devices provide accurate readings only if all conditions, such as calibration, temperature, and pressure, are strictly maintained. Traditional volumetric flow meters—like variable area meters or turbine flow meters—are inherently limited in detecting or compensating for temperature and pressure changes, which may result in deviations from true mass flow. For this reason, direct mass flow meters, particularly Coriolis mass flow meters and thermal mass flow meters, are preferred in many precision-driven applications.
The Coriolis effect describes how a moving rotating mass creates a force—known as the Coriolis force—that acts on a body in motion, causing an apparent deflection. Coriolis flow meters leverage this principle to provide highly accurate, direct mass flow measurements. Coriolis flow meters consist of a vibrating tube or tubes. When a fluid or gas flows through the vibrating tube, the mass causes the tube to twist or shift—a phenomenon directly proportional to the mass flow rate.
This phase shift in vibration is measured, generating a linear output signal that represents the mass flow rate. Coriolis mass flow meters are versatile—capable of measuring both liquids and gases—including slurries and viscous fluids—making them valuable in applications ranging from fuel dispensing, blending, and chemical injection to food processing and sanitary applications. Furthermore, by determining the natural frequency changes in the vibrating tube, Coriolis meters can also measure the fluid's density, enabling the calculation of volumetric flow rate and even detecting multi-phase flow or density anomalies.
Coriolis flow meters are known for their high accuracy, robustness, minimal pressure drop, and ability to handle a wide range of flow rates. As such, they are often the preferred solution where exact mass measurement is critical for quality control, safety, or regulatory compliance.
The diagram below demonstrates the core elements of the Coriolis flow meter operating principle:
Indirect mass flow measurement involves determining mass flow based on related properties or measurements, especially when direct measurement is impractical or cost-prohibitive. In engineering practice, this usually involves using volumetric flow meters—such as magnetic, ultrasonic, positive displacement, vortex, and turbine meters—combined with additional sensors (for pressure and temperature) and a flow computer. By monitoring volumetric flow along with pressure and temperature data, the true mass flow can be calculated according to the relevant equations of state.
Industries often use indirect mass flow measurement techniques in systems transporting compressed air, natural gas, steam, or other process gases, where the composition, density, or conditions may change. Indirect approaches are advantageous in large-diameter pipelines and where non-invasive measurements are needed. However, these rely on accurate compensation algorithms and frequent calibration to prevent measurement errors. When direct mass flow metering is unfeasible, indirect measurement offers a reliable alternative for mass flow monitoring, process optimization, and compliance documentation.
Differential Pressure (DP) flow meters are among the most established technologies for measuring flow rate in industrial automation, process engineering, and utility management. Operating on Bernoulli’s principle, DP flow meters generate a pressure drop by forcing fluid through a constriction (such as an orifice plate, venturi tube, or flow nozzle), converting the resulting pressure differential into a flow rate measurement. This technology is trusted for its wide range, simplicity, and compatibility with liquids, gases, and steam.
Modern DP meters often use multiple orifice plates or a Wheatstone bridge configuration to enhance measurement precision—this approach is especially common in critical flow assurance, energy management, and custody transfer applications. Accurate measurement depends on proper installation, regular calibration, and integration with electronic transmitters or flow computers to convert the pressure differential into a standardized mass flow reading. DP flow meters are suitable for high-pressure, high-temperature, and corrosive environments, providing consistent performance and long-term reliability.
Thermal mass flow meters are specialized instruments for highly accurate gas flow measurement. They work by quantifying the heat transferred from a heated sensor element to the gas flowing past it. These flow meters contain two precision-engineered resistance temperature detectors (RTDs) at the probe tip—one heated, one functioning as a reference. As process gas flows over the sensor, it cools the heated RTD, and the resulting change in temperature is used to calculate actual mass flow.
Thermal mass flow meters are direct-measuring devices, unaffected by variations in gas composition, temperature, or pressure, making them ideal for measuring air, nitrogen, natural gas, biogas, carbon dioxide, and other industrial gases. Their low-maintenance, non-intrusive design allows installation in large pipes, ducts, or stacks for air pollution monitoring, combustion control, HVAC systems, and leak detection.
Application versatility, combined with multi-gas capability and strong turndown ratios, makes thermal mass flow meters a preferred choice for environmental compliance, energy efficiency monitoring, and industrial process optimization—especially in industries targeting reduction of greenhouse gas emissions and compliance with regulatory reporting standards.
Turbine flow meters are a longstanding and widely utilized technology for both liquid and gas flow measurement. They operate with a rotor fitted with angled blades—the flow turns the rotor at a speed proportional to the flow velocity, which is sensed using magnetic pickups or optical sensors. Turbine meters offer a robust mechanical method, often used in petroleum, water treatment, chemical, and food-processing industries for custody transfer, blending, and batch control operations.
Advanced designs feature enhancements that minimize bearing wear, lower pressure drop, and enable measurement in bi-directional flow. Digital electronics paired with turbine meters allow for signal conditioning, pulse output, and improved integration with SCADA and control systems. However, proper installation and flow conditioning are essential for maintaining high measurement accuracy.
Selecting the optimal mass flow meter depends on factors such as the process fluid or gas type, flow range, operating pressure and temperature, required measurement accuracy, pipe size, installation environment, available budget, and maintenance requirements. For direct, highly accurate measurement in complex or variable conditions, Coriolis and thermal mass flow meters are typically recommended. For large infrastructure applications and when cost or retrofitting is a concern, indirect methods using DP, turbine, or ultrasonic flow meters may be more suitable.
Collaborate with experienced mass flow meter manufacturers and flow measurement experts to properly match the instrument to your specific application. Consider factors such as product certifications, compliance with industry standards (e.g., ISO, ASME, API), and after-sales support. Accurate flow measurement will not only optimize production efficiency and quality control, but also support energy conservation and environmental compliance.
If you are evaluating flow monitoring solutions, research options from leading Coriolis, thermal, and DP mass flow meter suppliers, and make use of available online resources and application calculators to compare products based on technical specifications, industry fit, and total cost of ownership.
Flow measurement in industrial applications can occur in either an open channel or closed conduit. Open channel flow meters measure fluids moving through spaces exposed to the atmosphere, relying on gravity as the driving force, while closed conduit systems employ enclosed pipelines or vessels, with flow induced by pressure differences. Understanding these fundamental distinctions is critical when selecting the most accurate flow measurement technology for various liquid and gas flow applications.
There is a wide range of mass flow meter types, each specifically engineered for diverse industrial processes and fluid properties. Accurate mass flow measurement is important for ensuring process efficiency, quality control, and regulatory compliance. This discussion will focus on several key categories of mass flow meters: Coriolis, ultrasonic, thermal, turbine, differential pressure, positive displacement, vortex, gyroscopic meters, and other specialized flow measurement instruments.
Coriolis mass flow meters operate by channeling fluid through U-shaped or straight vibrating tubes that oscillate in an angular harmonic motion. The Coriolis effect causes a phase shift in tube vibration that is directly related to the mass flow rate. These meters are known for their high measurement accuracy with precisions better than ±0.1%, broad turndown ratios exceeding 100:1, and built-in density measurement capabilities.
Coriolis flow meters are widely used in chemical, food & beverage, oil & gas, and pharmaceutical industries due to their reliability in measuring the mass flow of liquids and gases. They feature multi-parameter measurement, recording not only mass flow but also fluid density and temperature. Their robust design enables consistent performance across a range of fluids with varying viscosities and flow rates, making them a preferred choice where precise process control is essential.
Thermal mass flow meters, while sometimes confused with Coriolis meters, offer a different measurement principle and are particularly valued for processes where low-pressure drop, direct mass flow measurement, and minimal maintenance are required. Their operation is independent of external temperature and pressure compensation, enhancing their value in challenging gas flow measurement applications.
Thermal mass flow meters feature two precisely positioned heated sensors in the flow stream. As the process fluid moves, it absorbs heat from one sensor, creating a measurable temperature differential that translates directly to the fluid’s mass flow rate. By leveraging changes in heat transfer, these meters deliver accurate, repeatable flow readings for gases such as air, natural gas, nitrogen, or other industrial gases.
Thermal mass flow technology excels in HVAC, wastewater treatment, manufacturing, and environmental monitoring—particularly where managing air or gas flow is crucial. Their accuracy hinges on precise calibration that accounts for process temperature, pressure, heat capacity, and viscosity. While ideal for direct gas measurement, they offer limited utility with changing fluid compositions or for measuring liquids with variable thermal conductivity.
Two common types of turbine mass flow meters are impeller and twin turbine. Both utilize the kinetic energy of the moving fluid to spin turbine vanes. The rotational velocity of these vanes, detected by magnetic or optical sensors, is proportional to volumetric or mass flow rate. These meters are favored for their robustness and rapid response time, offering accuracy of 2% for gases or steam and 1.5% for liquids. However, because turbine meters are velocity-based, their accuracy may decrease in the presence of flow pulsation or non-laminar flow.
Impeller Turbine Mass Flow Meters - In an impeller mass flow meter, the fluid stream passes through two rotating elements: an impeller and a turbine. The impeller, powered by a synchronous motor via a magnetic coupling, imparts rotation to the fluid. Downstream, the turbine absorbs the momentum, producing a torque proportional to the fluid's mass flow. The angular deflection of the turbine, maintained by a spring, yields a direct measurement of the flow rate.
Twin Turbine Mass Flow Meter - Twin turbine mass flow meters work on fluid inertia principles. Both turbines are mounted on the same shaft, tied with a flexible torsion element. Measurement pickups and embedded magnets ensure accurate rotational signal capture. As mass flow increases, the phase shift between turbines increases, resulting in precise mass flow rate measurements, even at varying velocities.
A gyroscopic mass flow meter operates using principles similar to the Coriolis mass flow meter. It features a C-shaped pipe and a T-shaped leaf spring that resonates like a tuning fork. Energized by an electromagnetic field, the tuning fork imparts Coriolis-type acceleration, producing deflection proportional to the mass flow. This unique design enhances sensitivity, providing high-resolution mass flow readings for both liquid and gas applications.
The gyroscopic flow meter transforms tiny pipe deflections into precise electrical signals via pulse width modulation (PWM), ensuring accurate measurement across varying flow rates. These meters are ideal for high-precision low-flow monitoring, including advanced biotechnology, semiconductor, and specialty chemical processes.
Calorimetric flow meters, a subset of thermal flow meters, determine mass flow and volumetric flow rates by measuring temperature differences in fluid flow. With two heat sensors and a heating element, calorimetric meters leverage the thermal cooling effect as fluid velocity increases. Their non-invasive measurement style minimizes pressure drop and makes them suitable for pure gases and clean liquids, such as in medical diagnostics, process automation, and laboratory research.
Industrial flow switches are control devices that monitor liquid or gas flow in piping systems. They use reed switches, paddles, or relays to detect changes in flow and immediately transmit this information to control systems. These switches act as safeguards, automatically shutting off pumps or triggering alarms to prevent system damage or process interruptions. Flow switches are commonly installed in water treatment facilities, HVAC systems, and hydraulic or pneumatic circuits as part of predictive maintenance strategies for operational safety.
Unlike traditional analog or mechanical flow measuring devices, a digital flow meter utilizes electronic and software-based sensor technology—such as magnetic or ultrasonic transducers—to provide highly accurate and real-time flow data. Digital meters integrate seamlessly with SCADA systems and process automation platforms, allowing for dynamic monitoring, remote flow diagnostics, and enhanced data logging. Digital flow meters reduce human error, simplify calibration, and are compatible with multi-parameter measurement functions, supporting advanced industrial IoT solutions and smart process control.
Air flow meters are specialized instruments engineered to measure air flow velocity, volume, and mass across a wide spectrum of environments, from industrial ventilation to laboratory processes. Besides air, many models can measure gases such as nitrogen, helium, hydrogen, and more. Air flow measurement technologies include hot wire anemometers, vane types, cup anemometers, and pitot tubes. Each design offers unique advantages for HVAC, emissions monitoring, and process control, providing repeatable accuracy, quick response, and adaptability to changing flow profiles or system conditions.
Fuel flow meters are critical for fleet management, marine shipping, and industrial boilers, where fuel efficiency and consumption have a significant impact on operational costs. Accurately measuring the mass flow of diesel, gasoline, or fuel oil is essential for regulatory compliance and cost control. Many fuel meters employ Coriolis, ultrasonic, or positive displacement technologies tailored for fuel’s variable viscosity and fluctuating temperature. By delivering precise, real-time throughput data, fuel flow meters improve efficiency and simplify calibration across diverse fuels and flow rates.
An orifice plate flow meter is a classic differential pressure flow meter, prized for its durability, low installation cost, and simple design. The orifice plate restricts flow, generating a pressure differential that can be directly related to volumetric or mass flow rate via established flow equations. Common in water, steam, gas, and oil measurements, orifice plate flow meters offer reliable accuracy under steady-state flow conditions. Modern installations often connect orifice meters to transmitters and remote monitoring systems for continuous flow measurement and process optimization.
Water flow meters cover a variety of design types—paddle wheel, positive displacement, magnetic, and ultrasonic flow meters are among the most common. The correct selection depends on application criteria such as open or closed channel, liquid quality, required flow range, accuracy, and installation limitations. Precise water metering ensures efficient distribution, leak detection, and regulatory compliance in municipal water distribution, industrial production, and agricultural irrigation. Most systems provide real-time digital readouts and can interface with building management and controls for optimized water resource management.
Peak flow meters are portable medical devices designed to monitor respiratory health by measuring a patient’s peak expiratory flow (PEF). These meters are easy to use and provide fast, reliable readings (in liters per minute), making them invaluable for asthma management, airway obstruction diagnostics, and tracking lung function trends. Accurate peak flow monitoring can help detect early signs of respiratory distress, supporting individualized treatment adjustments and timely clinical intervention.
Microfluidic thermal flow sensors, or microfluidic mass flow meters, are engineered for precise measurement of ultra-low flow rates in complex liquid flow systems, such as biomedical research, drug discovery, micro-chemistry, and lab-on-a-chip technologies. Operating at the scale of femtoliters (one quadrillionth of a liter), microfluidic flow monitoring ensures accuracy and reproducibility in micro-scale experimentation. Their compact digital design supports high-throughput screening, consistent sample analysis, and integration with advanced automation.
Selecting the optimal mass flow meter for your application requires a careful evaluation of several key factors. Consider the process fluid’s characteristics (such as viscosity, aggressiveness, and cleanliness), the required measurement range, accuracy and repeatability standards, and compatibility with process conditions like pressure and temperature. Installation restrictions, maintenance requirements, and total cost of ownership should also influence meter selection. For critical processes, choosing a flow measurement solution equipped with diagnostic, data communication, and remote monitoring capabilities can provide ongoing reliability and process transparency.
Additionally, energy efficiency, safety compliance, ease of integration with digital control systems, and calibration protocols are important criteria, especially in industries seeking to comply with ISO, EPA, or industry-specific standards. Understanding the differences between volumetric flow meters, velocity meters, and direct mass flow measurement technology allows buyers and engineers to match meter types precisely to their intended use—whether measuring liquids, gases, or multiphase flows. For a guide to customer applications and best practices in industrial flow measurement, consult a trusted manufacturer or process automation specialist.
Mass flow measurement can be categorized into mass or volumetric types. Mass flow gauges the number of molecules within a gas, while volumetric flow assesses the space between these molecules. Both measurements are affected by changes in pressure and temperature.
Volumetric flow rate quantifies the three-dimensional volume a gas occupies as it moves through the device under specific pressure and temperature conditions, reflecting the true flow rate.
Mass flow meters determine the number of molecules passing through the instrument, expressed as a volumetric flow rate based on the space these molecules occupy at standard temperature and pressure.
Mass flow meters deliver data through various measurements and rely on the force exerted by the flowing stream when it impacts an obstruction, which can also offer a velocity measurement.
Gas and liquid flow are measured in units such as liters or kilograms per second, reflecting density. For liquids, density remains constant regardless of external conditions, whereas gases are affected by changes in pressure and temperature.
When pumping liquids or gases for energy applications, the flow rate is often measured in gigajoules per hour or BTUs per day. A flow computer calculates the energy flow rate using both mass and volumetric flow rates.
Measuring gases can be challenging because their volume fluctuates with changes in temperature, pressure, or heating. Gas flow rates on mass flow meters might be indicated as actual or standard, including units such as acm/h (actual cubic meters per hour), sm3/sec (standard cubic meters per second), kscm/h (thousand standard cubic meters per hour), or MMSCFD (million standard cubic feet per day).
Thermal, Coriolis, and controller meters are among the most effective for measuring gas flow rates.
The units for measuring liquids vary by application and industry, and can include gallons per minute, liters per second, bushels per minute, or cubic meters per second.
The Venturi effect describes the reduction in fluid pressure that occurs when the fluid flows through a constricted section of a pipe. As the fluid velocity increases in the narrowed area, its pressure decreases. This pressure drop is balanced by the increase in velocity.
To measure fluid velocity in a pipe using the Venturi effect, Bernoulli's equation is applied, which indicates that as the velocity of a liquid increases, the pressure decreases proportionally. The flow rate is often expressed in gallons per minute, liters per second, or cubic meters per second. It is calculated using the formula Q = A Ă— v, where Q represents the liquid flow rate, A is the pipe's cross-sectional area in square meters, and v is the velocity of the liquid in meters per second.
A flow meter's performance is evaluated based on its error rate and measurement precision. The accuracy of a flow meter is typically expressed as a percentage of:
In evaluating flow rate accuracy, it's important to present calculations as percentages relative to the actual flow rate, categorized as minimum, normal, or maximum. These metrics are crucial for choosing the appropriate mass flow meter for specific applications.
Monitoring the flow of liquids and gases demands continuous attention to ensure precise and accurate measurements. Any errors in readings, calculations, or adjustments can lead to reduced efficiency and possible damage to equipment. Identifying the root causes of issues with meter readings can help avert repairs and production delays. The following are some conditions that might cause challenges with mass flow meter readings or lead to meter damage.
Slurry consists of tiny particles ranging from less than 60 to 100 microns and can be categorized as either settling or non-settling. These particles can be abrasive, causing wear on flow meters, or they may coagulate and block the flow path.
In open systems, exposed to the air, impurities, and air can be blended with a fluid to form bubbles. In vortex flow meters, air bubbles prevent the creation of vortices. In ultrasonic flow meters, they prevent ultrasonic waves resulting in malfunctions and inaccurate readings.
In a straight pipe, the flow velocity of a fluid is typically consistent and steady. However, bends or angles in the pipe can disrupt this uniformity, leading to changes in flow velocity and causing it to become irregular, either deviating from the center or creating swirling patterns. The extent of measurement error will vary based on the degree of these irregularities.
Pulsations arise from the acceleration and deceleration of fluid flow, potentially surpassing the mass flow meter’s measurement range. This results in meter readings that underestimate the actual flow rate. Reciprocating pumps are a common source of this issue. To mitigate pulsations, a damper like an accumulator can be used, or the response time of the flow meter can be extended.
There are many varieties of ways that pipes can be caused to vibrate, which include the operation of machinery near the pipe or the opening and closing of valves. In some instances, when a fluid is introduced into a pipe, it can cause a vibration. Coriolis and vortex meters will not provide proper measurements in those conditions. This is not true of ultrasonic flow meters, which are not influenced by vibrations.
Scaling happens when tiny metal particles from groundwater crystallize and adhere to pipe walls. Over time, this buildup narrows the flow path, restricting liquid movement. Scaling can also affect flow meters, particularly those with paddle wheels or floating components, leading to inaccuracies in their measurements.
Slime consists of living organisms like algae, bacteria, and microorganisms, and can be either sticky or muddy. Similar to scaling, rust, sludge, and slurry, slime can obstruct a mass flow meter by clogging it or impeding fluid flow. Additionally, the electrical conductivity of slime may lead to inaccurate measurements.
The calorimetric principle enables the measurement of flow velocity and media pressure. It uses two sensors to track heat transfer and determine the flow rate, independent of the media's electrical conductivity, viscosity, or density.
The measurement process relies on the cooling effect of the media on a heated sensor. The mass of the media affects the extent of cooling experienced by the sensor. The media must release heat from its highest temperature, and this heat transfer is calculated based on the temperature difference and mass flow rate. This method measures changes in the state variables of the media to compute heat transfer accurately.
A Coriolis flow meter measures mass by the inertia of a liquid or gas flowing through a vibrating tube that is equipped with a set of sensors at the inlets and outlets of the meter. The increased movement of the flow produces measurable oscillation that is proportional to the mass...
A flow switch is a device that measures the flow rate and liquid pressure within a duct, loop, or system. Flow sensor and flow indication are other names for this switch. The primary purpose of a flow switch is to...
A magnetic flow meter is a volumetric flow meter that uses electrodes connected to the liquid flow to measure the velocity of fluids in a tube or pipe. The unique design of magnetic flow meters allows them to take their readings without the need for any moving parts...
A rotameter is a device that measures the flow of fluid volume per unit time in a closed tube. There are diverse rotameters applications, including chemical injection/dosing and tank blanketing. A rotameter can be said...
An ultrasonic flow meter measures the flow of a liquid or gas by sending ultrasonic waves across a pipe, containing the flow in the direction of the flow and in the opposite direction of the flow. The ultrasonic waves and the velocity of...
A flow meter is a flow rate measuring device used to determine the linear or nonlinear mass and volumetric flow of a liquid or a gas. The many names of flow meters include flow gauge, flow indicator, liquid meter, and flow rate sensor...