Flow transmitters provide electrical outputs that are proportional to flow inputs. They use flow meters to measure the flow of liquids and gases. Flow transmitters output analog voltages, analog currents, frequencies and pulses. Analog voltage outputs are simple, usually linear, functions of the measurement. They are continuous rather than pulsed or discrete. Analog current outputs are suitable for sending signals over long distances. They include current loops such as 4 – 20 mA and use feedback to provide an appropriate current regardless of impedance or noise. Frequency and pulse signal outputs are encoded via amplitude modulation (AM), frequency modulation (FM), and pulse width modulation (PWM). They are also expressed as sine waves and pulse trains. Some flow transmitters are inserted perpendicular to the flow path and require a threaded-hole pipe for access. Others are inserted parallel to the flow patch between two pieces of process pipes and clamped into place. |
Products & Services Related to Flow Transmitters
Liquid Flow Switches, Volumetric
Volumetric liquid flow switches are devices with a switch output used for measuring the flow or quantity of a moving fluid in terms of a unit of volume per unit time, such as liters per minute.
Paddlewheel Flow Meters
Paddlewheel flow meters have a paddle wheel that is perpendicular to the flow path. The rotor axis is positioned to limit contact between the paddles and the flowing media.
Positive Displacement Flow Meters
Positive displacement flow meters measure the volume or flow rate of a moving fluid or gas by dividing the media into fixed, metered volumes. These devices consist of a chamber that obstructs the media flow and a rotating or reciprocating mechanism that allows the passage of fixed-volume amounts.
Rotameters
Rotameters are typically tapered glass tubes positioned vertically in the fluid flow. A float within the tube rides upward in relation to the amount of flow.
Turbine Flow Meters
Turbine flow meters measure the rate of flow in a pipe or process line via a rotor that spins as the media passes through its blades.
Velocity Flow Switches
Gas flow switches and liquid flow switches, velocity, are used to measure the flow or quantity of a moving fluid in terms of velocity, such as feet per minute.
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.
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Engineering Web: Flow Transmitters - Machine Design
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Electrical/Electronic Monthly - August, 2007
A second channel measures resistance, voltage, or 4-to20-mA current. The process version has 24-V loop power for calibration of temperature transmitters. All field-metrology wells have an LCD display ...
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