Fundamentals of Multivariable Measurement?


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What is Multivariable measurement ?

Measuring multiple process variable in one instrument in order to accurately measure volume as well as mass flow through appropriate flow compensation.

Flow compensation is divided up in to two

1.Standard Compensation
2. Dynamic Compensation - Multivariable transmitters are used for Dynamic Compensation.

What is standard flow compensation ?

The process if measuring the differential pressure produced a primary flow element,the absolute pressure and the temperature of the flowing and using these measurement to compensate for variation in density to calculate the mass flow of the fluid.

What is dynamic flow compensation ?

The process of measuring the differential pressure produced by a primary flow element,the absolute pressure and the temperature of the flowing media and using these measurement with other data (pipe size,bore and type of flow element etc) to compensate for error producing variables while calculating flow rate.

Multivariable transmitters compensate for the following variable to increase mass flow accuracy over a larger flow turndown.
-Discharge Coefficient
-Gas expansion factor
-Thermal expansion factor
-Velocity of approach actor
-Viscosity
-Density

Dynamic Compensation of Flow measurement

What are the functions available in Multivariable transmitters?

Multivariable transmitters measures Static Pressure,Differential pressure and Process temperature.

Multivariable transmitters calculate Density/Viscosity,Beta ratio,Gas expansion,Discharge coefficient, Velocity of approach,Reynolds number.

Multivariable transmitters indicates and transmits DP,SP,PT and Flow mass/Flow Volume.

Applications of Multivarible Technology

Liquid/Gas measurement
Steam measurement - Super heated and saturated.

What are the advantages of Multivariable Measurement?

1.Three measurement in one device
2.Minimized wiring,control and installation hardware.
3.Minimized process intrusion and leakage.
4.Improved accuracy.
5.Reduced installation cost.
6.Reduced Maintenance.