Technical data

Flow meter FC01-Ex Flow meter FC01-Ex
Technical implementation of customer calibration 29 Technical implementation of customer calibration 29
4.2.4 Zero point, directional discrimination and upper characteristic curve value
The zero point of the characteristic curve and the zero point of flow need not be identical. If the
zero point of the characteristic curve - lowest trim point - is above the zero point of flow, the
characteristic curve is linearly extrapolated down by 10% MBE (= upper measuring range value)
so as to extend the calibration range of the FC01-Ex.
However, the extrapolation is only effected to the theoretical zero point as the measuring system
does not operate in a direction-selective way.
If the zero point of flow and the zero point of the characteristic curve are identical, the control
variable should be increased by 300 to 400 digits to suppress the convection-dependent variation
of the zero point.
In the same way that the calibration range can be extrapolated downward by 10% MBE, so can
the upper calibration range be extrapolated by 10% MBE above the upper trim point. Error
indication because of minor over limits of the upper calibration range values can thus be eliminated.
The extended characteristic range will then be fully available when determining the analogue output,
the limit values and the bar graph.
4.2.5 New curve / Old curve
4.2.5.1 New curve
The following automatic processes have been provided for to facilitate and accelerate the calibration
or manual entry of a new curve.
1. Preloading of zero point control variables
As a result of parasitic heat transfer points a big part (approx. 50%) of the heating power is
not transported through the medium but rather through the housing and the electrical
cables. The heating power control variable with zero flow has already a value above 25,000
digits.* Preloading the setting value for the lower trim point with that value obviates the need
for passing through a wide setting range (timesaving benefit).
* Provided the temperature differential has been selected appropriately (see para. 4.2.1 for
recommended values).
2. Linear preloading of interim values for velocity and control variable
The calibration range left between the last addressed and established trim point and the zero
point is linearly divided among the remaining trim points. This applies both to velocity quantities
and control variables. It generally ensures that only a small calibration range needs to be
passed (provided that 1. has been satisfied).
In this operating mode - new curve - an already existing curve (old curve) would be deleted.
If the new curve is completely entered by hand, it is necessary to enter the TK reference
temperature (see 5.1.1.4.7) when quitting the menu.
The TK reference temperature is the medium temperature at which the curve was estab-
lished under normal operating temperature conditions.
If the calibration of a new curve is made selecting temperature differences which are essentially
smaller than the values recommended, the zero point on the characteristic curve will be
displaced towards smaller control variables. It may happen then that the first trim value is
below or on the preloaded zero point value, in which case the software will provide that the
initial values for further control variables are below the established preceding value.
4.2.4 Zero point, directional discrimination and upper characteristic curve value
The zero point of the characteristic curve and the zero point of flow need not be identical. If the
zero point of the characteristic curve - lowest trim point - is above the zero point of flow, the
characteristic curve is linearly extrapolated down by 10% MBE (= upper measuring range value)
so as to extend the calibration range of the FC01-Ex.
However, the extrapolation is only effected to the theoretical zero point as the measuring system
does not operate in a direction-selective way.
If the zero point of flow and the zero point of the characteristic curve are identical, the control
variable should be increased by 300 to 400 digits to suppress the convection-dependent variation
of the zero point.
In the same way that the calibration range can be extrapolated downward by 10% MBE, so can
the upper calibration range be extrapolated by 10% MBE above the upper trim point. Error
indication because of minor over limits of the upper calibration range values can thus be eliminated.
The extended characteristic range will then be fully available when determining the analogue output,
the limit values and the bar graph.
4.2.5 New curve / Old curve
4.2.5.1 New curve
The following automatic processes have been provided for to facilitate and accelerate the calibration
or manual entry of a new curve.
1. Preloading of zero point control variables
As a result of parasitic heat transfer points a big part (approx. 50%) of the heating power is
not transported through the medium but rather through the housing and the electrical
cables. The heating power control variable with zero flow has already a value above 25,000
digits.* Preloading the setting value for the lower trim point with that value obviates the need
for passing through a wide setting range (timesaving benefit).
* Provided the temperature differential has been selected appropriately (see para. 4.2.1 for
recommended values).
2. Linear preloading of interim values for velocity and control variable
The calibration range left between the last addressed and established trim point and the zero
point is linearly divided among the remaining trim points. This applies both to velocity quantities
and control variables. It generally ensures that only a small calibration range needs to be
passed (provided that 1. has been satisfied).
In this operating mode - new curve - an already existing curve (old curve) would be deleted.
If the new curve is completely entered by hand, it is necessary to enter the TK reference
temperature (see 5.1.1.4.7) when quitting the menu.
The TK reference temperature is the medium temperature at which the curve was estab-
lished under normal operating temperature conditions.
If the calibration of a new curve is made selecting temperature differences which are essentially
smaller than the values recommended, the zero point on the characteristic curve will be
displaced towards smaller control variables. It may happen then that the first trim value is
below or on the preloaded zero point value, in which case the software will provide that the
initial values for further control variables are below the established preceding value.