Vortex Flow Meters

Vortex flow meters are flow sensors that detect the frequency of vortices shed by a bluff body placed in a flow stream. The frequency of the vortices is proportional to the flow velocity. Vortex flow meters are used to measure the flow of liquids and/or gases. Some devices can accommodate mixed-phase materials such as steam. Others can measure liquids with suspended solids (slurries). Operating pressure range and media temperature range are important media specifications to consider. Operating pressure range is the maximum head pressure of the process media that devices can withstand. Maximum temperature range is the maximum temperature of the media that can be monitored. Additional parameters include velocity flow rate, which is usually measured in distance/time. Vortex flow meters that can also measure temperature, density or media levels are commonly available.

Pipe size and mounting style are important consideration when selecting vortex flow meters. Many products are calibrated in terms of pipe diameter, a measurement that is expressed in English units such as inches (in) or metric units such as centimeters (cm). There are several mounting styles for vortex flow meters. Insertion-type devices are inserted perpendicular to the flow path. They usually require a threaded hole in the process pipe, or another means of access. In-line flanged devices are inserted parallel to the flow path, typically between two pieces of flanged process piping. In-line threaded products are inserted parallel to the flow path and threaded into two existing process pipes. National pipe thread (NPT) is the most common thread type. In-line clamp vortex flow meters are also available. These devices are inserted parallel to the flow path and clamped between two existing process pipes.

Vortex flow meters differ in terms of outputs and interfaces. Flow rate information can be output as an analog voltage signal, an analog current signal, a frequency or pulse, or a switch. Analog voltage signals such as 0 – 10 mV are a simple, usually linear function of the measurement. They are continuous, rather than pulsed or discrete. Analog current signals such as 4 – 20 mA use feedback to provide the appropriate current regardless of line noise and impedance. These devices, which are often called transmitters, are useful when sending signals over long distances. Flow rate information can also be output as an encoded signal via amplitude modulation (AM) or frequency modulation. Vortex flow meters with switch outputs use media flow to trigger a switch based on preset flow rates. Both serial and parallel computer interfaces are commonly available. Serial interfaces include RS232, RS422, and RS485. Parallel interfaces use the general-purpose interface bus (GPIB), a Centronics port, or a printer port.

Vortex flow meters provide a variety of features. Multi-insertion devices determine the flow rate by taking flow rate measurements across several points in the flow path. Programmable flow meters typically include a built-in microprocessor and can be adjusted electronically for different materials, ranges, and outputs. Devices with recorder or totalizer functions can plot or chart flow history for a given unit of time. Some vortex flow meters include built in audible or visual alarms and not just alarm contacts. Others provide controller functions. Products that are rated for sanitary applications are suitable for medical or food processing applications.

• Flow Research Magazine Special Report: Multi-Variable Vortex Flow Meters (.pdf)
  In a "Worldflow Special Report," Flow Research magazine discusses Nice Instrumentation's new line of multi-variable vortex flow meters. This article also notes how a recent American Petroleum...
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• Vortex Plate Brings Innovation and Simplicity to Vortex Flow Measurement (.pdf)
  Problem: Traditional Vortex Flow Meters are susceptible to common mode noise, leaking sensor diaphragms, o-ring replacement, leaks into sensor cavity and electronics, and repeatability drift....
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• Magnetic Inductive Flow Meters (.pdf)
  Magnetic inductive flow meters use Faraday's law of inductance to measure flow rates in electrically conductive fluids. Other technologies used to measure flow rate include paddle wheel, vortex and...
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Part Numbers for Vortex Flow Meters