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 - FS-100-250 is a Flow Switch for Threaded Plastic Piping featuring Liquid, 2.5 GPM Switch Point, 50 VA SPST, 3/4 ", NPT Female, ± 10 % Accuracy, PP, and 12 " (300mm) Wire L. Part of the FS-100 Series. Sold individually.
$115.18
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FSW205P-PC is a Flow Switch with Relay featuring Liquid, 5.68 LPM to 56.8 LPM, 1/2 ", NPT Female, ± 2 %, 5 A SPDT, PP, Polycarbonate, Buna, Acetal, SS, and 150 psi. Part of the FPR200 Series. Sold individually.
$389.06
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FT-PLCD240-04 is a Plastic Quick Coupling Insert featuring Plug, Threaded, 1/4 " NPT Male, Straight, Acetal, and Shutoff. Part of the FT-PLC Series. Sold individually.
$25.44
Should ship between 08 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FTB-840-I is a Turbine Flow Meter featuring Liquid, 4.4 GPM to 88 GPM (16.65 LPM to 333.12 LPM), 2 ", NPT Male, ± 0.5 %, 4 mA to 20 mA, 304, 316, CD4MCU SS, and Tungsten Carbide. Part of the FTB-800 Series. Sold individually.
$1,972.63
Should ship between 01 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FTB601B is a Flow Sensor featuring All Plastic Ultra-Low, Liquid, 0.1 LPM to 2 LPM, 1/4 ", Barbed, ± 1 %, Amplified Square Wave, PVDF, and FKM. Part of the FTB600B Series. Sold individually.
$1,008.17
Should ship between 12 Nov and 15 Nov
Subject to factory lead times
The Dwyer - FV103 is a Vortex Shedding Flow Meter featuring 2.5 GPM to 25 GPM, 3/4 " NPT Female, ± 2 %, 10 Vdc to 30 Vdc, 4 mA to 20 mA, 125 mA SPST SSR, Brass, PVDF, FKM O-RING, and LCD Display. Part of the FV101 Series. Sold individually.
$1,289.42
Should ship between 12 Jan and 19 Jan
Subject to factory lead times
The Dwyer - HHF144B is a Hygro-Thermo Anemometer featuring Handheld, Rotating Metal Vane, Battery Power (3 AA), 40 FPM to 7800 FPM, ± 1 % Accuracy, 2-3/4 " x 2.8 " (DxL), NIST Cert, and Volume Calculation. Part of the HHF144 Series. Sold individually.
$1,910.33
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - SYS/FP7002A/FP7030-GI is a Paddlewheel Sensor/Transmitter System featuring 12 Vdc to 18 Vdc, 25 GPM to 460 GPM, 3 ", NPT Female, ± 2 % Accuracy, Amplified Square Pulse, Galvanized Iron, and 150 psi. Part of the FP7002 Series. Sold individually.
$1,143.49$1,240.28
Should ship between 01 Dec and 15 Dec
Subject to factory lead times
Configure product to see pricing
The KOBOLD NKP level switch offers an affordable yet highly reliable solution for side-mounted liquid level detection in challenging chemical environments, thanks to its polypropylene or PVDF construction that stands up to aggressive media. Engineered with remarkable simplicity and functionality, this compact device features a magnetic float mechanism that delivers consistent performance with minimal maintenance requirements, making it ideal for long-term deployment in industrial applications. The versatile design allows for easy switch function conversion from normally open to normally closed by simply rotating the unit 180°, providing installation flexibility without additional components or reconfiguration. With NEMA 6/IP68 protection and hermetically sealed reed switch technology, the NKP maintains operational integrity even in harsh environments and can withstand pressures up to 145 PSIG and temperatures up to 212°F (PVDF version). Particularly valuable for vessels with limited top or bottom access, this side-mounting level switch combines practical engineering with excellent chemical compatibility to deliver dependable level control across a wide range of industrial applications.
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The Dwyer - BV2000BRN250A is a Vision Turbine Flow Meter featuring Low Cost, Liquid, 0.8 GPM to 6.6 GPM (3 LMP to 25 LMP), 3/8 ", NPT Male, ± 3 %, Amplified Square Wave, Brass, PTFE, and Graphite. Part of the 3-Pin Mini DIN BV2000 Series. Sold individually.
$177.82
Should ship between 09 Feb and 16 Feb
Subject to factory lead times
The Dwyer - BV2000TRN100A is a Vision Turbine Flow Meter featuring NSF/ANSI Certified, Liquid, 1 LPM to 10 LPM, 3/8 ", NPT Male, ± 3 %, Amplified Square Wave, Trogamid, PTFE, Graphite, and 3-Pin Mini DIN. Part of the BV2000 Series. Sold individually.
$113.86
Should ship between 09 Feb and 16 Feb
Subject to factory lead times
The Dwyer - BV2000TRN350B is a Vision Turbine Flow Meter featuring NSF/ANSI Certified, Liquid, 2 LPM to 35 LPM, 3/8 ", NPT Male, ± 3 %, Amplified Square Wave, Trogamid, PTFE, and Graphite. Part of the BV2000 Series. Sold individually.
$125.22
Should ship between 09 Feb and 16 Feb
Subject to factory lead times
The Dwyer - DPF144W is a Flow Meter Indicator featuring Rate, Total, Pulse, Contact Closure, 45 Vdc, 1-Input, Wall Mount, 6.5 Hz, 2 DC Pulse, and 5/8 Digit Dual Display. Part of the DPF140 Series. Sold individually.
$836.15
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FL-2041 is a Variable Area Flow Meter featuring Air, 2 LPM to 20 LPM, 100 psi, 1/8 " NPT Female, ± 3 %, Direct Read, Acrylic, Buna, PVC, and w/Valve. It is rated for a temperature range of 65 °C (150 °F). Part of the FL-2000 Series. Sold individually.
$122.97
Should ship between 15 Dec and 22 Dec
Subject to factory lead times
The Dwyer - FL6715A is a Flow Meter featuring Pneumatic, In-line, Air, 15 SCFM to 150 SCFM, 1000 psi, 1/2 " NPT Female, ± 2 %, Direct Read, 302 SS, Al, Polyphenylene Sulfide, and Ceramic. It is rated for a temperature range of 116 °C (240 °F). Part of the FL6700A Series. Sold individually.
$410.44
Should ship between 01 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FL904G is a Flow Meter w/SS Enclosure featuring Heavy Duty, Water, 1.26 GPM to 12.6 GPM, 250 psi, 1 " NPT Female, ± 2 %, Direct Read, 316L SS, Glass, Polycarbonate, and EPR. It is rated for a temperature range of 93 °C (200 °F). Part of the FL900-G Series. Sold individually.
$2,491.29
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FLC-W15 is a Variable Area Flow Meter featuring Clear In-line, Water, 1.5 GPM to 15 GPM, 325 psi, 1 " NPT Female, ± 5 %, Direct Read, Brass, Polycarbonate, SS, Polysulfone, and Buna. It is rated for a temperature range of 93 °C (200 °F). Part of the FLC Series. Sold individually.
$299.48
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FLDA3201C is a Variable Area Flow Meter featuring Air, 0.22 SCFH to 2.2 SCFH, 200 psi, 1/8 " NPT Female, ± 5 %, Direct Read, Aluminum, Glass, Buna, Carboloy, and w/Valve. It is rated for a temperature range of 121 °C (250 °F). Part of the FLD Series. Sold individually.
$209.55
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FLDA3219G is a Variable Area Flow Meter featuring Air, 0.7 mL/min to 7 mL/min, 200 psi, 1/8 " NPT Female, ± 5 %, Direct Read, Aluminum, Glass, Buna, and w/Valve. It is rated for a temperature range of 121 °C (250 °F). Part of the FLD Series. Sold individually.
$209.55
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FLDN3502G is a Variable Area Flow Meter featuring Nitrogen, 0.2 LPM to 2 LPM, 200 psi, 1/8 " NPT Female, ± 5 %, Direct Read, 316 SS, Glass, FKM, and w/Valve. It is rated for a temperature range of 121 °C (250 °F). Part of the FLD Series. Sold individually.
$512.07
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FLR1008-P is a Turbine Flow Meter featuring Low-Flow, Liquid, 20 mL/min to 200 mL/min, 1/4 ", Compression Fitting, ± 3 %, 0 Vdc to 5 Vdc, Amplified Square Wave, PPS, Glass, SS, Sapphire, and FKM. Part of the FLR1000 Series. Sold individually.
$584.68
Should ship between 08 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FMA-1609A-I is a Mass Flow Meter featuring Gas, 0.25 SLM to 50 SLM, RS232, 145 psi, 1/4 " NPT Female, 4 mA to 20 mA, LCD, ± 0.8 %, 300 SS, Al, Silicone, FKM, and Supply Incl. It is rated for a temperature range of 50 °C (122 °F). Part of the FMA-1600A Series. Sold individually.
$2,312.38
Should ship between 17 Nov and 24 Nov
Subject to factory lead times
The Dwyer - FMA-1613A is a Mass Flow Meter featuring Gas, 5 SLM to 1000 SLM, RS232, 145 psi, 3/4 " NPT Female, 0 Vdc to 5 Vdc, LCD, ± 0.8 %, 300 SS, Al, Silicone, FKM, and Supply Incl. It is rated for a temperature range of 50 °C (122 °F). Part of the FMA-1600A Series. Sold individually.
$3,865.54
Should ship between 15 Dec and 22 Dec
Subject to factory lead times
The Dwyer - FMA-A2409 is a Mass Flow Controller featuring Gas, 0.1 SLM to 10 SLM, 250 psi, ± 1 %, 1/4 " NPT Female, 0 Vdc to 5 Vdc, 4 mA to 20 mA, w/Power Supply, LCD, 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.
$1,685.52
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FS-100-250 is a Flow Switch for Threaded Plastic Piping featuring Liquid, 2.5 GPM Switch Point, 50 VA SPST, 3/4 ", NPT Female, ± 10 % Accuracy, PP, and 12 " (300mm) Wire L. Part of the FS-100 Series. Sold individually.
$115.18
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FSW205P-PC is a Flow Switch with Relay featuring Liquid, 5.68 LPM to 56.8 LPM, 1/2 ", NPT Female, ± 2 %, 5 A SPDT, PP, Polycarbonate, Buna, Acetal, SS, and 150 psi. Part of the FPR200 Series. Sold individually.
$389.06
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FT-PLCD240-04 is a Plastic Quick Coupling Insert featuring Plug, Threaded, 1/4 " NPT Male, Straight, Acetal, and Shutoff. Part of the FT-PLC Series. Sold individually.
$25.44
Should ship between 08 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FTB-840-I is a Turbine Flow Meter featuring Liquid, 4.4 GPM to 88 GPM (16.65 LPM to 333.12 LPM), 2 ", NPT Male, ± 0.5 %, 4 mA to 20 mA, 304, 316, CD4MCU SS, and Tungsten Carbide. Part of the FTB-800 Series. Sold individually.
$1,972.63
Should ship between 01 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FTB601B is a Flow Sensor featuring All Plastic Ultra-Low, Liquid, 0.1 LPM to 2 LPM, 1/4 ", Barbed, ± 1 %, Amplified Square Wave, PVDF, and FKM. Part of the FTB600B Series. Sold individually.
$1,008.17
Should ship between 12 Nov and 15 Nov
Subject to factory lead times
The Dwyer - FV103 is a Vortex Shedding Flow Meter featuring 2.5 GPM to 25 GPM, 3/4 " NPT Female, ± 2 %, 10 Vdc to 30 Vdc, 4 mA to 20 mA, 125 mA SPST SSR, Brass, PVDF, FKM O-RING, and LCD Display. Part of the FV101 Series. Sold individually.
$1,289.42
Should ship between 12 Jan and 19 Jan
Subject to factory lead times
The Dwyer - HHF144B is a Hygro-Thermo Anemometer featuring Handheld, Rotating Metal Vane, Battery Power (3 AA), 40 FPM to 7800 FPM, ± 1 % Accuracy, 2-3/4 " x 2.8 " (DxL), NIST Cert, and Volume Calculation. Part of the HHF144 Series. Sold individually.
$1,910.33
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - SYS/FP7002A/FP7030-GI is a Paddlewheel Sensor/Transmitter System featuring 12 Vdc to 18 Vdc, 25 GPM to 460 GPM, 3 ", NPT Female, ± 2 % Accuracy, Amplified Square Pulse, Galvanized Iron, and 150 psi. Part of the FP7002 Series. Sold individually.
$1,143.49$1,240.28
Should ship between 01 Dec and 15 Dec
Subject to factory lead times
Configure product to see pricing
The KOBOLD NKP level switch offers an affordable yet highly reliable solution for side-mounted liquid level detection in challenging chemical environments, thanks to its polypropylene or PVDF construction that stands up to aggressive media. Engineered with remarkable simplicity and functionality, this compact device features a magnetic float mechanism that delivers consistent performance with minimal maintenance requirements, making it ideal for long-term deployment in industrial applications. The versatile design allows for easy switch function conversion from normally open to normally closed by simply rotating the unit 180°, providing installation flexibility without additional components or reconfiguration. With NEMA 6/IP68 protection and hermetically sealed reed switch technology, the NKP maintains operational integrity even in harsh environments and can withstand pressures up to 145 PSIG and temperatures up to 212°F (PVDF version). Particularly valuable for vessels with limited top or bottom access, this side-mounting level switch combines practical engineering with excellent chemical compatibility to deliver dependable level control across a wide range of industrial applications.
Configure Product
Configure product to see pricing
The Dwyer - BV2000BRN250A is a Vision Turbine Flow Meter featuring Low Cost, Liquid, 0.8 GPM to 6.6 GPM (3 LMP to 25 LMP), 3/8 ", NPT Male, ± 3 %, Amplified Square Wave, Brass, PTFE, and Graphite. Part of the 3-Pin Mini DIN BV2000 Series. Sold individually.
$177.82
Should ship between 09 Feb and 16 Feb
Subject to factory lead times
The Dwyer - BV2000TRN100A is a Vision Turbine Flow Meter featuring NSF/ANSI Certified, Liquid, 1 LPM to 10 LPM, 3/8 ", NPT Male, ± 3 %, Amplified Square Wave, Trogamid, PTFE, Graphite, and 3-Pin Mini DIN. Part of the BV2000 Series. Sold individually.
$113.86
Should ship between 09 Feb and 16 Feb
Subject to factory lead times
The Dwyer - BV2000TRN350B is a Vision Turbine Flow Meter featuring NSF/ANSI Certified, Liquid, 2 LPM to 35 LPM, 3/8 ", NPT Male, ± 3 %, Amplified Square Wave, Trogamid, PTFE, and Graphite. Part of the BV2000 Series. Sold individually.
$125.22
Should ship between 09 Feb and 16 Feb
Subject to factory lead times
The Dwyer - DPF144W is a Flow Meter Indicator featuring Rate, Total, Pulse, Contact Closure, 45 Vdc, 1-Input, Wall Mount, 6.5 Hz, 2 DC Pulse, and 5/8 Digit Dual Display. Part of the DPF140 Series. Sold individually.
$836.15
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FL-2041 is a Variable Area Flow Meter featuring Air, 2 LPM to 20 LPM, 100 psi, 1/8 " NPT Female, ± 3 %, Direct Read, Acrylic, Buna, PVC, and w/Valve. It is rated for a temperature range of 65 °C (150 °F). Part of the FL-2000 Series. Sold individually.
$122.97
Should ship between 15 Dec and 22 Dec
Subject to factory lead times
The Dwyer - FL6715A is a Flow Meter featuring Pneumatic, In-line, Air, 15 SCFM to 150 SCFM, 1000 psi, 1/2 " NPT Female, ± 2 %, Direct Read, 302 SS, Al, Polyphenylene Sulfide, and Ceramic. It is rated for a temperature range of 116 °C (240 °F). Part of the FL6700A Series. Sold individually.
$410.44
Should ship between 01 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FL904G is a Flow Meter w/SS Enclosure featuring Heavy Duty, Water, 1.26 GPM to 12.6 GPM, 250 psi, 1 " NPT Female, ± 2 %, Direct Read, 316L SS, Glass, Polycarbonate, and EPR. It is rated for a temperature range of 93 °C (200 °F). Part of the FL900-G Series. Sold individually.
$2,491.29
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FLC-W15 is a Variable Area Flow Meter featuring Clear In-line, Water, 1.5 GPM to 15 GPM, 325 psi, 1 " NPT Female, ± 5 %, Direct Read, Brass, Polycarbonate, SS, Polysulfone, and Buna. It is rated for a temperature range of 93 °C (200 °F). Part of the FLC Series. Sold individually.
$299.48
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FLDA3201C is a Variable Area Flow Meter featuring Air, 0.22 SCFH to 2.2 SCFH, 200 psi, 1/8 " NPT Female, ± 5 %, Direct Read, Aluminum, Glass, Buna, Carboloy, and w/Valve. It is rated for a temperature range of 121 °C (250 °F). Part of the FLD Series. Sold individually.
$209.55
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FLDA3219G is a Variable Area Flow Meter featuring Air, 0.7 mL/min to 7 mL/min, 200 psi, 1/8 " NPT Female, ± 5 %, Direct Read, Aluminum, Glass, Buna, and w/Valve. It is rated for a temperature range of 121 °C (250 °F). Part of the FLD Series. Sold individually.
$209.55
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FLDN3502G is a Variable Area Flow Meter featuring Nitrogen, 0.2 LPM to 2 LPM, 200 psi, 1/8 " NPT Female, ± 5 %, Direct Read, 316 SS, Glass, FKM, and w/Valve. It is rated for a temperature range of 121 °C (250 °F). Part of the FLD Series. Sold individually.
$512.07
Should ship between 24 Nov and 01 Dec
Subject to factory lead times
The Dwyer - FLR1008-P is a Turbine Flow Meter featuring Low-Flow, Liquid, 20 mL/min to 200 mL/min, 1/4 ", Compression Fitting, ± 3 %, 0 Vdc to 5 Vdc, Amplified Square Wave, PPS, Glass, SS, Sapphire, and FKM. Part of the FLR1000 Series. Sold individually.
$584.68
Should ship between 08 Dec and 15 Dec
Subject to factory lead times
The Dwyer - FMA-1609A-I is a Mass Flow Meter featuring Gas, 0.25 SLM to 50 SLM, RS232, 145 psi, 1/4 " NPT Female, 4 mA to 20 mA, LCD, ± 0.8 %, 300 SS, Al, Silicone, FKM, and Supply Incl. It is rated for a temperature range of 50 °C (122 °F). Part of the FMA-1600A Series. Sold individually.
$2,312.38
Should ship between 17 Nov and 24 Nov
Subject to factory lead times
The Dwyer - FMA-1613A is a Mass Flow Meter featuring Gas, 5 SLM to 1000 SLM, RS232, 145 psi, 3/4 " NPT Female, 0 Vdc to 5 Vdc, LCD, ± 0.8 %, 300 SS, Al, Silicone, FKM, and Supply Incl. It is rated for a temperature range of 50 °C (122 °F). Part of the FMA-1600A Series. Sold individually.
$3,865.54
Should ship between 15 Dec and 22 Dec
Subject to factory lead times
The Dwyer - FMA-A2409 is a Mass Flow Controller featuring Gas, 0.1 SLM to 10 SLM, 250 psi, ± 1 %, 1/4 " NPT Female, 0 Vdc to 5 Vdc, 4 mA to 20 mA, w/Power Supply, LCD, 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.
$1,685.52
Should ship between 24 Nov and 01 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.