Calculation Of Level And Densities - Endress+Hauser Proservo NMS5 Operating Instructions Manual

6 Operation
52
6.6

Calculation of Level and Densities

The section specifies the formula used by NMS5 to calculate levels and densities.
Gas
Density Negligible
Measured Displacer Weight W
Upper Liquid
Density
Measured Displacer Weight Wu
Middle Liquid
Density
Measured Displacer Weight Wm
Bottom Liquid
Density
Measured Displacer Weight Wb
Figure. 56: Calculation of Levels and Densities
Surface and Interface Levels
While the measured surface or interface level is constant, the displacer rests at the balancing position. The ten-
sion on the measuring wire is proportional to the displacer weight diminished by the buoyancy forces in both
layers:
Level
Liquid Level
Upper Surface
Middle Surface
A rise or fall of the level will increase or decrease the submerged volume. If this change exceeds the volume
tolerance set at matrix position GVH=345 "VOLUME TOLERANCE", then the
corresponding change will actuate the motor of the NMS5 till the balancing condition is fulfilled again.
Tank Bottom Level
For bottom level measurement, the balancing condition is defined as
Measuring Wire
Tension T
Formula
T = W - Vвρu
T = W - Vвρm - (V - Vв) ρu
T = W - Vвρb - (V - Vв) ρm
Proservo NMS5
Displacer
Volume V
Balance
Volume V
B
Endress+Hauser