Contrec 414L, Руководство по введению, Страница: 39 / 82

414L-M-V3
The above figure shows the temperature-density points for a 4 point table.
Above tp4, the curve has the same gradient as between tp3 and tp4, and
below tp1, the curve has the same gradient as between tp1 and tp2.
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 rogrammed during Calibration.
For differential pressure devices, the Gross Total is calculated as:
Temperature Compensation 37
DENSITY
T E MP . t p 3
t p 2 t p 1 t p 4
Dens 1
Dens 4
Volume Flow = S x A
1
2
x
1
Density
1
2