Contrec 414L, Руководство по введению, Страница: 43 / 82

414L-M-V3
4.6 DENSITY CORRECTION
Density correction is available on the Model 414LA where a density meter
is connected across the temperature inputs (Terminal 5) in place of a
temperature transmitter. The densitometer must have a 4-20mA output.
During Calibration, the density at 4mA and 20mA can be programmed and
the mass flow for volumetric flowmeters is:
Mass Flowrate = R x Density
where R is the flowrate defined in Sections 3.3.1 and 3.3.2.
Density is the density input.
If the input falls below 3.5mA, an error status, "Err 12" is displayed.
Differential Pressure Devices
For differential pressure devices the Mass flowrate is defined as:
Mass Flow = S x A
½
x Density
½
where S = Mass Flowrate at 20mA
(Density at reference conditions)
½
The Mass flowrate at 20mA and the corresponding reference density are
provided by the flowmeter supplier and S is then calculated from the above
equation and programmed during Calibration.
The Gross Total is calculated as:
Temperature Compensation 41
Volume Flow = S x A
1
2
x
1
Density
1
2