How Multivariable Transmitters Work ~ Learning Instrumentation And Control Engineering Learning Instrumentation And Control Engineering

How Multivariable Transmitters Work

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A multivariable transmitter is a differential pressure transmitter that is capable of measuring a number of independent process variables, including differential pressure, static pressure, and temperature. When used as a mass flow transmitter, these independent values can be used to compensate for changes in density, viscosity and other flow parameters. A typical multivariable transmitter installation and setup for flow measurement is shown below:
Multivariable Transmitter Installation & SetUp
A Multivariable transmitter delivers unprecedented performance and capabilities by providing three separate
measurements in one simple, easy-to-use solution, so you can realize a significant reduction in installed cost.

When used in DP flow measurement applications, it measures process pressure, temperature and differential  pressure simultaneously and dynamically calculates 'real time', fully-compensated mass  flow. Fully compensated mass flow reduces sources of traditional DP flow uncertainty caused by pressure and temperature variations. A multivariable transmitter used in DP flow measurement greatly increases accuracy to as high as ±0.8% and increases DP flow rangeability from 3:1 to 14:1.

Key Advantages of Multivariable Transmitters in Flow Measurement Applications
(1) Compensate flow readings for changes in line pressure and process temperature
(2) Maximize insight into process conditions with flow calculations that update
     many times a second
(3) Reduce pipe penetrations and save on impulse piping and connection systems
     with three measurements in a single device
(4) ±0.8% flow accuracy over 14:1 flow turndown
(5) Capable of measuring variables such as: Mass, Volumetric and Energy Flow, Totalized Flow, Differential Pressure, Static Pressure (Gage and Absolute),
Process Temperature.
(6) Can produce a 4-20 mA HART output

Key Application Areas

(1) Gas and natural gas measurement
(2) Saturated and superheated steam measurement
(3) Liquid measurement

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