Flow Control
Explore our comprehensive range of Flow Control products, featuring precision instruments such as flow meters, flow switches, flow transmitters, and flow sensors. Our offerings cater to diverse applications, ensuri...
Categories in Flow Control Products (6)
Flow Meters
Flow meters are a piece of essential equipment for many industries, as they allow for accurately measuring fluid flow rates. At Centro, we carry a complete online selection of flow meters, including magnetic flow meters, turbine flow meters, and positive displacement flow meters. We also offer a variety of accessories and replacement parts to ensure that your flow meter always operates at peak efficiency. Whether you're looking for a new flow meter or need to restock your supplies, Centro has everything you need to keep your operation running smoothly.
Flow Switches
Flow switches are vital instruments in fluid systems that detect the presence or absence of flow. These devices ensure proper operation and prevent issues such as pump damage or system failure. Flow switches are employed in various industries to monitor and control the flow of liquids or gases, providing a reliable means of safeguarding equipment and optimizing fluid processes.
Flow Transmitters
Flow Transmitters are essential in fluid systems, accurately measuring and transmitting flow rate data. These devices play a critical role in monitoring and controlling the flow of liquids or gases in various applications. By providing real-time information, Flow Transmitters enable precise adjustments, ensuring optimal performance and efficiency. Their reliability and accuracy make them indispensable for industries where precise flow measurement is crucial.
Flow Sensors
Flow Sensors are key elements in fluid systems, detecting and measuring the flow rate. These devices offer real-time data on liquid or gas movement, enabling precise control and monitoring. Flow Sensors are essential in manufacturing, healthcare, and environmental monitoring industries, providing valuable insights for process optimization, quality control, and regulatory compliance.
Flow, pH & Conductivity Meters, Transmitters & Controllers
Centro offers a wide range of flow, pH, and conductivity meters, transmitters, and controllers to meet the demands of various industrial and commercial applications. From monitoring flow rates and maintaining chemical balance for fluid quality and consistency, our solutions are engineered for precision, reliability, and seamless integration. We provide products such as magnetic and ultrasonic flow meters, pH controllers, and conductivity transmitters designed to optimize performance in industries like water treatment, food and beverage, chemical processing, and pharmaceuticals.
Whether you need accurate measurements, durable equipment, or easy system integration, Centro has the expertise and products to support your operations. Explore our selection online or contact our team to find the right solution for your application and ensure peak system efficiency.
Flow Control Accessories
Flow Control Accessories encompass a range of supplementary components designed to optimize, support, or enhance the operation of primary flow control equipment such as valves, regulators, actuators, and pumps. These accessories are critical in ensuring precise control, safety, and efficiency within fluid and gas systems across industrial, commercial, and residential applications.
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The Dwyer - DPF76 is a Frequency Input Ratemeter/Totalizer featuring Total, Pulse, 110 Vac, 1-Input, 1/8 DIN, 10 kHz, 2 Relays, and 6 Digit Single Display. Part of the DPF76 Series. Sold individually.
$429.12
Should ship between 17 Nov and 24 Nov
Subject to factory lead times
The Dwyer - FL-75A is a Variable Area Flow Meter featuring Low Cost Industrial, Water, 0.5 GPM to 5 GPM, 150 psi, 1 " NPT Female, ± 3 %, Direct Read, 316 SS, Polysulfone, EPR, PVC, and Acrylic. It is rated for a temperature range of 54 °C (130 °F). Part of the FL-75 Series. Sold individually.
$418.60
Should ship between 12 Nov and 15 Nov
Subject to factory lead times
The Dwyer - FLK-2212 is a Variable Area Flow Meter featuring Air, 0.3 LPM to 3 LPM, 125 psi, 1/8 " NPT Female, ± 4 %, Direct Read, Acrylic, Brass, SS, Silicone Rubber, and w/Valve. It is rated for a temperature range of 60 °C (140 °F). Part of the FLK-2000 Series. Sold individually.
$97.87
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FLR6105D is an Indicating Flow Meter w/Analog Output featuring Oil, 0.5 GPM to 5 GPM, 3500 psi, 1/2 " NPT Female, Digital, Brass, T302 SS, Carbon Steel, Silicone, PPS, Ceramic, and FKM. Part of the FLR Series. Sold individually.
$1,313.01
Should ship between 01 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FMA-A2306 is a Mass Flow Meter featuring Gas, 0.01 SLM to 1 SLM, 250 psi, 1/4 " NPT Female, 0 Vdc to 5 Vdc, 4 mA to 20 mA, LCD, ± 1 %, 17-4 SS, Acetal, and FKM. It is rated for a temperature range of 50 °C (122 °F). Part of the FMA-A2000 Series. Sold individually.
$1,136.01
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FMA1842A is a Mass Flow Meter featuring Economical, Gas, 1 SLM to 100 SLM, 1000 psi, 3/8 " Compression, 0 Vdc to 5 Vdc, 4 mA to 20 mA, LCD, ± 1 %, Al, Brass, and FKM. It is rated for a temperature range of 50 °C (122 °F). Part of the FMA1800A Series. Sold individually.
$1,538.97
Should ship between 01 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FP-5201 is a Flow Sensor featuring Rugged, Reliable, All-Metal, 1.6 FPS to 20 FPS, ± 1 % Accuracy, Sinusoidal, 316 SS, 1500 psi, and 1.25 " to 12 " Pipe. Part of the FP-5200 Series. Sold individually.
$898.83
Should ship between 15 Dec and 22 Dec
Subject to factory lead times
The Dwyer - FPR205-PC is a Flow Transmitter with Visual Indication featuring Liquid, 5.68 LPM to 56.8 LPM, 1/2 ", NPT Female, ± 2 %, 4 mA to 20 mA, 316 SS, Polycarbonate, Buna, Acetal, and 200 psi. Part of the FPR200 Series. Sold individually.
$1,195.04
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FST-211-SPST is a Flow Switch featuring Thermal Dispersion, Liquid, 0.04 FPS to 3 FPS, 1 A SPST Relay, N.O/N.C, Selectable, 3/4 " to 1-1/2 ", NPT Male, ± 5 % Accuracy, PP, PVDF, and 10 " Wire L. Part of the FST-200 Series. Sold individually.
$326.67
Should ship between 15 Dec and 22 Dec
Subject to factory lead times
The Dwyer - FSW-30A is a Flow Switch featuring Non-Magnetic, Industrial, Water, 0.12 GPM to 8 GPM, 15 A SPDT, 1/2 ", NPT Female, Brass, 316 SS, Phosphor Bronze, and EPDM. Part of the FSW30 Series. Sold individually.
$854.90
Should ship between 12 Nov and 15 Nov
Subject to factory lead times
The Dwyer - FT-MC20-04 is a Ferruless Quick Coupling Insert featuring Plug, Compression Fitting, Straight, Chrome-Plated Brass, 1/4 " (OD), and Straight Thru. Part of the FT-MC Series. Sold individually.
$34.85
Should ship between 08 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FT-MC22-04 is a Quick Coupling Insert featuring Plug, Barbed, Straight, Chrome-Plated Brass, 1/4 " (ID), and Straight Thru. Part of the FT-MC Series. Sold individually.
$27.94
Should ship between 08 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FT-MCD21-04 is a Ferruless Quick Coupling Insert featuring Plug, Compression Fitting, 90 ° Elbow, Chrome-Plated Brass, 1/4 " (OD), and Shutoff. Part of the FT-MC Series. Sold individually.
$64.76
Should ship between 08 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FTB-1422-AMP is a Turbine Flow Meter featuring Economical, Liquid, 0.75 GPM to 7.5 GPM, 1 ", NPT Male, ± 1 %, Amplified Square Wave, 316 SS, and Tungsten Carbide. Part of the FTB-1400 Series. Sold individually.
$1,441.99
Should ship between 17 Nov and 24 Nov
Subject to factory lead times
Configure product to see pricing
The KOBOLD KAL-K thermal flow switch delivers exceptional monitoring performance for water-based liquids through advanced microprocessor-controlled technology with intelligent temperature compensation. Unlike conventional flow switches, this compact device maintains consistent readings across temperature fluctuations, making it ideal for applications requiring reliable flow monitoring in changing conditions. The robust design features no moving parts, making it extremely durable and insensitive to contaminants while providing remarkably low pressure loss in your system. With capabilities to handle flow velocities from 0.02 to 6.6 ft/sec and withstand temperatures up to 250°F and pressures to 1450 PSIG, the KAL-K offers versatility across numerous industrial applications.
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The Dwyer - DPF64 is an Analog Input Ratemeter/Totalizer featuring Rate, Current/Voltage, 110 Vac, 1-Input, 1/8 DIN, 5 Hz, 2 Relays, and 6 Digit Single Display. Part of the DPF60 Series. Sold individually.
$550.05
Should ship between 17 Nov and 24 Nov
Subject to factory lead times
The Dwyer - FL-2012-SS is a Variable Area Flow Meter featuring Air, 0.2 LPM to 2.5 LPM, 100 psi, 1/8 " NPT Female, ± 5 %, Direct Read, SS, Acrylic, FKM, and w/Valve. It is rated for a temperature range of 65 °C (150 °F). Part of the FL-2000 Series. Sold individually.
$169.04
Should ship between 15 Dec and 22 Dec
Subject to factory lead times
The Dwyer - FL-3010SA is a Variable Area Flow Meter w/PTFE Valves featuring 29.9 SCCM to 299 SCCM Air, 0.47 SCCM to 4.7 SCCM Water, 100 psi, 1/8 " FNPT, ± 2 %, 0 to 150, and w/Valve. It is rated for a temperature range of 65 °C (150 °F). Part of the FL-3000 Series. Sold individually.
$458.77
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FL-9010 is an Easy-View Flow Meter featuring Water, 1 GPM to 10 GPM, 325 psi, 1 " NPT Female, ± 5 %, Direct Read, T300 SS, and Polysulfone. It is rated for a temperature range of 121 °C (250 °F). Part of the FL-9000 Series. Sold individually.
$120.74
Should ship between 09 Feb and 16 Feb
Subject to factory lead times
The Dwyer - FLK-2201 is a Variable Area Flow Meter featuring Air, 0.2 SCFH to 2 SCFH, 125 psi, 1/8 " NPT Female, ± 4 %, Direct Read, Acrylic, Brass, SS, Silicone Rubber, and w/Valve. It is rated for a temperature range of 60 °C (140 °F). Part of the FLK-2000 Series. Sold individually.
$97.87
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FLR1007 is a Turbine Flow Meter featuring Low-Flow, Liquid, 13 mL/min to 100 mL/min, 1/8 ", Compression Fitting, ± 3 %, 0 Vdc to 5 Vdc, PPS, Glass, SS, Sapphire, and FKM. Part of the FLR1000 Series. Sold individually.
$473.80
Should ship between 08 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FMA5520A is a Mass Flow Controller featuring Economical, Gas, 0.25 SLM to 10 SLM, 1000 psi, ± 1 %, 1/4 " Compression Fitting, 0 Vdc to 5 Vdc, 4 mA to 20 mA, Std, LCD, Al, Brass, and FKM. It is rated for a temperature range of 50 °C (122 °F). Part of the FMA5500A Series. Sold individually.
$1,472.42
Should ship between 01 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FMG3001-PP is an Electromagnetic Flow Meter featuring Conductive Fluids, 0.15 FPS to 16.4 FPS, 1/2 " to 4 ", FP-5300 Sensor Installation, ± 1 %, Amplified Square Wave, 316 SS, PP, and FKM. Part of the FMG3000 Series. Sold individually.
$1,432.67
Should ship between 15 Dec and 22 Dec
Subject to factory lead times
The Dwyer - FT-LM200-04 is a Ferruless Coupling Insert featuring Plug, Compression Fitting, Straight, Chrome-Plated Brass, 1/4 " (OD), Multiple Mount, Straight Thru, and 1/4 " Flow. Part of the FT-LM Series. Sold individually.
$58.20
Should ship between 08 Dec and 15 Dec
Subject to factory lead times
The Dwyer - DPF76 is a Frequency Input Ratemeter/Totalizer featuring Total, Pulse, 110 Vac, 1-Input, 1/8 DIN, 10 kHz, 2 Relays, and 6 Digit Single Display. Part of the DPF76 Series. Sold individually.
$429.12
Should ship between 17 Nov and 24 Nov
Subject to factory lead times
The Dwyer - FL-75A is a Variable Area Flow Meter featuring Low Cost Industrial, Water, 0.5 GPM to 5 GPM, 150 psi, 1 " NPT Female, ± 3 %, Direct Read, 316 SS, Polysulfone, EPR, PVC, and Acrylic. It is rated for a temperature range of 54 °C (130 °F). Part of the FL-75 Series. Sold individually.
$418.60
Should ship between 12 Nov and 15 Nov
Subject to factory lead times
The Dwyer - FLK-2212 is a Variable Area Flow Meter featuring Air, 0.3 LPM to 3 LPM, 125 psi, 1/8 " NPT Female, ± 4 %, Direct Read, Acrylic, Brass, SS, Silicone Rubber, and w/Valve. It is rated for a temperature range of 60 °C (140 °F). Part of the FLK-2000 Series. Sold individually.
$97.87
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FLR6105D is an Indicating Flow Meter w/Analog Output featuring Oil, 0.5 GPM to 5 GPM, 3500 psi, 1/2 " NPT Female, Digital, Brass, T302 SS, Carbon Steel, Silicone, PPS, Ceramic, and FKM. Part of the FLR Series. Sold individually.
$1,313.01
Should ship between 01 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FMA-A2306 is a Mass Flow Meter featuring Gas, 0.01 SLM to 1 SLM, 250 psi, 1/4 " NPT Female, 0 Vdc to 5 Vdc, 4 mA to 20 mA, LCD, ± 1 %, 17-4 SS, Acetal, and FKM. It is rated for a temperature range of 50 °C (122 °F). Part of the FMA-A2000 Series. Sold individually.
$1,136.01
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FMA1842A is a Mass Flow Meter featuring Economical, Gas, 1 SLM to 100 SLM, 1000 psi, 3/8 " Compression, 0 Vdc to 5 Vdc, 4 mA to 20 mA, LCD, ± 1 %, Al, Brass, and FKM. It is rated for a temperature range of 50 °C (122 °F). Part of the FMA1800A Series. Sold individually.
$1,538.97
Should ship between 01 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FP-5201 is a Flow Sensor featuring Rugged, Reliable, All-Metal, 1.6 FPS to 20 FPS, ± 1 % Accuracy, Sinusoidal, 316 SS, 1500 psi, and 1.25 " to 12 " Pipe. Part of the FP-5200 Series. Sold individually.
$898.83
Should ship between 15 Dec and 22 Dec
Subject to factory lead times
The Dwyer - FPR205-PC is a Flow Transmitter with Visual Indication featuring Liquid, 5.68 LPM to 56.8 LPM, 1/2 ", NPT Female, ± 2 %, 4 mA to 20 mA, 316 SS, Polycarbonate, Buna, Acetal, and 200 psi. Part of the FPR200 Series. Sold individually.
$1,195.04
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FST-211-SPST is a Flow Switch featuring Thermal Dispersion, Liquid, 0.04 FPS to 3 FPS, 1 A SPST Relay, N.O/N.C, Selectable, 3/4 " to 1-1/2 ", NPT Male, ± 5 % Accuracy, PP, PVDF, and 10 " Wire L. Part of the FST-200 Series. Sold individually.
$326.67
Should ship between 15 Dec and 22 Dec
Subject to factory lead times
The Dwyer - FSW-30A is a Flow Switch featuring Non-Magnetic, Industrial, Water, 0.12 GPM to 8 GPM, 15 A SPDT, 1/2 ", NPT Female, Brass, 316 SS, Phosphor Bronze, and EPDM. Part of the FSW30 Series. Sold individually.
$854.90
Should ship between 12 Nov and 15 Nov
Subject to factory lead times
The Dwyer - FT-MC20-04 is a Ferruless Quick Coupling Insert featuring Plug, Compression Fitting, Straight, Chrome-Plated Brass, 1/4 " (OD), and Straight Thru. Part of the FT-MC Series. Sold individually.
$34.85
Should ship between 08 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FT-MC22-04 is a Quick Coupling Insert featuring Plug, Barbed, Straight, Chrome-Plated Brass, 1/4 " (ID), and Straight Thru. Part of the FT-MC Series. Sold individually.
$27.94
Should ship between 08 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FT-MCD21-04 is a Ferruless Quick Coupling Insert featuring Plug, Compression Fitting, 90 ° Elbow, Chrome-Plated Brass, 1/4 " (OD), and Shutoff. Part of the FT-MC Series. Sold individually.
$64.76
Should ship between 08 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FTB-1422-AMP is a Turbine Flow Meter featuring Economical, Liquid, 0.75 GPM to 7.5 GPM, 1 ", NPT Male, ± 1 %, Amplified Square Wave, 316 SS, and Tungsten Carbide. Part of the FTB-1400 Series. Sold individually.
$1,441.99
Should ship between 17 Nov and 24 Nov
Subject to factory lead times
Configure product to see pricing
The KOBOLD KAL-K thermal flow switch delivers exceptional monitoring performance for water-based liquids through advanced microprocessor-controlled technology with intelligent temperature compensation. Unlike conventional flow switches, this compact device maintains consistent readings across temperature fluctuations, making it ideal for applications requiring reliable flow monitoring in changing conditions. The robust design features no moving parts, making it extremely durable and insensitive to contaminants while providing remarkably low pressure loss in your system. With capabilities to handle flow velocities from 0.02 to 6.6 ft/sec and withstand temperatures up to 250°F and pressures to 1450 PSIG, the KAL-K offers versatility across numerous industrial applications.
Configure Product
Configure product to see pricing
The Dwyer - DPF64 is an Analog Input Ratemeter/Totalizer featuring Rate, Current/Voltage, 110 Vac, 1-Input, 1/8 DIN, 5 Hz, 2 Relays, and 6 Digit Single Display. Part of the DPF60 Series. Sold individually.
$550.05
Should ship between 17 Nov and 24 Nov
Subject to factory lead times
The Dwyer - FL-2012-SS is a Variable Area Flow Meter featuring Air, 0.2 LPM to 2.5 LPM, 100 psi, 1/8 " NPT Female, ± 5 %, Direct Read, SS, Acrylic, FKM, and w/Valve. It is rated for a temperature range of 65 °C (150 °F). Part of the FL-2000 Series. Sold individually.
$169.04
Should ship between 15 Dec and 22 Dec
Subject to factory lead times
The Dwyer - FL-3010SA is a Variable Area Flow Meter w/PTFE Valves featuring 29.9 SCCM to 299 SCCM Air, 0.47 SCCM to 4.7 SCCM Water, 100 psi, 1/8 " FNPT, ± 2 %, 0 to 150, and w/Valve. It is rated for a temperature range of 65 °C (150 °F). Part of the FL-3000 Series. Sold individually.
$458.77
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FL-9010 is an Easy-View Flow Meter featuring Water, 1 GPM to 10 GPM, 325 psi, 1 " NPT Female, ± 5 %, Direct Read, T300 SS, and Polysulfone. It is rated for a temperature range of 121 °C (250 °F). Part of the FL-9000 Series. Sold individually.
$120.74
Should ship between 09 Feb and 16 Feb
Subject to factory lead times
The Dwyer - FLK-2201 is a Variable Area Flow Meter featuring Air, 0.2 SCFH to 2 SCFH, 125 psi, 1/8 " NPT Female, ± 4 %, Direct Read, Acrylic, Brass, SS, Silicone Rubber, and w/Valve. It is rated for a temperature range of 60 °C (140 °F). Part of the FLK-2000 Series. Sold individually.
$97.87
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FLR1007 is a Turbine Flow Meter featuring Low-Flow, Liquid, 13 mL/min to 100 mL/min, 1/8 ", Compression Fitting, ± 3 %, 0 Vdc to 5 Vdc, PPS, Glass, SS, Sapphire, and FKM. Part of the FLR1000 Series. Sold individually.
$473.80
Should ship between 08 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FMA5520A is a Mass Flow Controller featuring Economical, Gas, 0.25 SLM to 10 SLM, 1000 psi, ± 1 %, 1/4 " Compression Fitting, 0 Vdc to 5 Vdc, 4 mA to 20 mA, Std, LCD, Al, Brass, and FKM. It is rated for a temperature range of 50 °C (122 °F). Part of the FMA5500A Series. Sold individually.
$1,472.42
Should ship between 01 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FMG3001-PP is an Electromagnetic Flow Meter featuring Conductive Fluids, 0.15 FPS to 16.4 FPS, 1/2 " to 4 ", FP-5300 Sensor Installation, ± 1 %, Amplified Square Wave, 316 SS, PP, and FKM. Part of the FMG3000 Series. Sold individually.
$1,432.67
Should ship between 15 Dec and 22 Dec
Subject to factory lead times
The Dwyer - FT-LM200-04 is a Ferruless Coupling Insert featuring Plug, Compression Fitting, Straight, Chrome-Plated Brass, 1/4 " (OD), Multiple Mount, Straight Thru, and 1/4 " Flow. Part of the FT-LM Series. Sold individually.
$58.20
Should ship between 08 Dec and 15 Dec
Subject to factory lead times
FAQS
- Measuring flow rate in a pipe requires a flow meter matched to the fluid type, pipe size, flow range, and accuracy requirement. For conductive liquids (water, chemicals, slurries), magnetic flow meters are the most popular choice — they have no moving parts, create no pressure drop, and handle dirty or abrasive fluids. For non-conductive liquids or retrofit installations where you can't cut the pipe, clamp-on ultrasonic flow meters mount externally and measure through the pipe wall. For applications requiring the highest accuracy or mass flow measurement (batching, custody transfer), Coriolis meters measure mass flow directly. For steam and gas, vortex meters are robust and widely used. For simple, low-cost local visual indication of flow rate, variable-area meters (rotameters) provide a direct reading without power or electronics. Flow switches are used when you only need to confirm flow is present or absent — for example, verifying cooling water is running before allowing a machine to start. The flow meter output (typically 4–20 mA) feeds back to a PLC or controller for monitoring, totalization, or closed-loop flow control.
- The flow meter technology must match the fluid type, pipe size, accuracy requirement, and process conditions. Magnetic (mag) flow meters measure conductive liquids (water, chemicals, slurries) using Faraday's law — they have no moving parts, handle dirty or abrasive fluids well, and are the default for water and wastewater applications. Ultrasonic flow meters (transit-time and Doppler) are non-intrusive and can be clamp-on, ideal for retrofit or applications where the pipe cannot be cut. Coriolis meters measure mass flow directly with very high accuracy — the premium choice for custody transfer, batching, and applications requiring density measurement. Vortex meters are robust and versatile for steam, gas, and liquid measurement in moderate-to-large pipe sizes. Variable-area meters (rotameters) provide simple, low-cost local visual indication of flow rate. Turbine meters offer high accuracy for clean, low-viscosity liquids. The best approach is to define the fluid properties, flow range, accuracy requirement, and installation constraints, then match to the technology that fits.
- A flow switch detects whether flow is present or absent (or above/below a threshold) and outputs a discrete on/off signal — it does not measure the actual flow rate. Flow switches are used for protection and alarm functions: confirming cooling water is flowing before allowing a machine to operate, detecting loss of lubrication flow to trigger a shutdown, or verifying that a pump is actually moving fluid. They are simpler and less expensive than flow meters. A flow meter, by contrast, measures the actual flow rate (GPM, liters/minute, SCFM, etc.) and provides a continuous analog or digital output proportional to the flow value. Flow meters are used when the control system needs to know how much fluid is flowing — for batching, dosing, energy accounting, and closed-loop flow control. If you only need to know whether flow is on or off, a flow switch is sufficient. If you need to know how much, you need a flow meter.
- A magnetic flow meter (mag meter) uses Faraday's law of electromagnetic induction to measure the velocity of a conductive liquid flowing through a pipe. The meter generates a magnetic field across the pipe, and the flowing conductive liquid produces a voltage proportional to its velocity — this voltage is measured by electrodes in the pipe wall and converted to a flow rate. Mag meters have several significant advantages: no moving parts (zero maintenance on the sensor itself), no obstruction to flow (full bore, no pressure drop), excellent performance with dirty, abrasive, and slurry-containing liquids, wide turndown ratios (typically 100:1 or greater), and bidirectional measurement capability. They are the standard choice for water and wastewater treatment, chemical processing, food and beverage, pharmaceutical, and pulp and paper applications. The main limitation is that the liquid must be electrically conductive (minimum ~5 µS/cm) — mag meters cannot measure hydrocarbons, deionized water, or gases.
- Flow meter sizing must balance accuracy, rangeability, and pressure drop. The meter should be sized so that the normal operating flow rate falls within the meter's optimal accuracy range — typically between 25% and 75% of its full-scale capacity. Sizing based solely on the pipe diameter is a common mistake — if the pipe is oversized for the actual flow rate (which is common in many installations), the flow velocity through the meter will be too low for accurate measurement. In these cases, the meter should be sized smaller than the pipe, with reducers and expanders installed to transition from the pipe size to the meter size. Key data needed for sizing includes the fluid type and properties (density, viscosity, conductivity, temperature, pressure), the minimum, normal, and maximum flow rates, the required accuracy, and the acceptable pressure drop. Most flow meter manufacturers provide online sizing tools where you input these parameters and receive a recommended meter size and model.