Operating Instructions
OIE 12en Edition 2019-02
7
Temperature compensation
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Temperature compensation
If the KRAL volumeter is additionally equipped with a temperature sensor, the current density of the
flowing fluid can be calculated from this measured value by means of a stored density table.
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At the option "Volume at X°", a normalized volume measurement is then possible at which the
displayed values are converted to a reference temperature X° that can be selected freely. This
ensures that measuring errors caused by changes in the density due to temperature variations are
avoided.
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The option "Volume at TempA" calculates the volume back to the temperature volumeter A. This
option allows the comparison with a reservoir level.
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Measuring errors are also reduced at the "Mass calculation" option, since the device can now
process the actual density and not only a stored mean value at the mass conversion. For the case of
operation with different fluids two different density tables can be entered and selected.
Differential measurement
The KRAL electronic unit can process the signals of two volumeters and determine and display the links
possible with it.
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The option differential measurement "A-B" allows the subtraction of the values of the two channels,
e.g. feed and return of a consumer supplied with a closed circular pipeline and thus allows the direct
display of the consumer of this device.
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The option sum "A+B" allows the addition of the two measured values and thus, for example, the
display of the total of two devices.
Circulation ratio and threshold value
The ratio A/(A-B) is called the "Circulation ratio". On the basis of the laws of error propagation, a strongly
rising error of the displayed differential value A-B results for the option "Differential measurement" at
values A/(A-B) >> 1, so that the value A/(A-B) can also be used to judge the reliability of a differential
measurement. For the case A/(A-B) >> 1, for example in the case of a deactivated consumer but with a
circulation pump that continues to be operated, a threshold value can be specified for A-B below which
the measured values are not taken into consideration for the sum calculation.
Averaging
A strongly fluctuating flow rate causes a jumping display or as a result a fluctuating analog output. The
averaging function reduces this effect by generating a averaging across several measured values. The
number of measured values for averaging can be set, see "3.06 Averaging analog output", Page 41, and
see "2.16 Averaging display rate", Page 39.
Limit value
The "Limit value bypass" function allows the automatic activation of a bypass valve when a volumeter
blocks. The bypass valve is actuated via Relay output 1, see "3.13 Function relay 1", Page 42.
Collective error message
When an error message occurs, Relay output 2 is switched for the collective error.
