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OIO 15en Edition 2020-05
Operating Instructions
Linearization
Function description
Linearization
The calibration certificate contains a mean K-factor that has been determined for the flow range 10:1
and that can therefore be used across a wide flow range. However, the K-factor shows slightly different
values at different flow rates. These are also documented in the enclosed calibration certificate. If
highest measuring precision is required, it is therefore advisable, especially at strongly varying flow
rates, to take these different values into consideration by means of a "Linearization". The K-factors are
therefore fed into a suitable flow management unit across several interpolation values of the flow rate.
The K-factor relevant for the flow rate being measured is then determined by means of linear
interpolation between the two nearest interpolation values.
The viscosity dependence of the K-factors must also be taken into account. These are determined
during calibration at a viscosity of approximately 4.2 mm²/s. The influence of the flow rate on the K-factor
decreases at higher viscosities so that the mean K-factor can then also be used in a considerably larger
flow range without noteworthy errors.
Temperature compensation
If the KRAL flowmeter is additionally equipped with a temperature sensor, the current density of the
flowing liquid can be calculated from this measured value by means of a density table stored in the flow
management unit. A normalized volume measurement is then possible at which the displayed values
are converted to a reference temperature that can be selected freely. This ensures that measuring
errors caused by changes in the density due to temperature variations are avoided.
Flow direction detection
Systems with a changing flow direction as well as systems with pressure pulsations - that can also
cause a reversal of the flow direction - require the use of a second pick up. This additional signal (90°
phase-offset) and the incremental encoding inputs available in the KRAL electronic unit can be used to
determine the direction of flow and to take it into consideration when calculating the total values.
Junction box
The manufacturer offers a junction box that facilitates the electrical connection of the various sensors for
the flowmeters of the OME series. For further information see "Accessories", page 35.
