Technical data

Flow Meter FC01-Ex Flow Meter FC01-Ex
28 Technical implementation of customer calibration 28 Technical implementation of customer calibration
4.2.2 Trim point selection - number and position
Between 2 and 20 trim points can be set.
They are addressed in a “downward” sequence to ensure the user can recognize the trim points
still available by the trim point index indicated.
A reasonable distribution on the characteristic curve depends on the desired accuracy, the
required measuring range or continuity criteria such as differentiating criteria. These issues are
addressed in section 9.
Generally, there are fewer trim points needed in the upper characteristic curve range than in the
lower range, the reason for this being the flattening characteristic curve (see section 9).
Depending on the medium and the measuring range, it is possible to use different procedures in
selecting the trim points.
A linear preselection of the trim points has been provided for in the FC01-Ex. With the appropriate
number of trim points set, this procedure achieves good results over the entire velocity range
(5 m/s with water, 25 m/s with air).
A trim point distribution which significantly reduces the measuring error when compared to a
linear distribution, can be determined by the following formula (see 9.2 - Example 2).
AB - trim value [m/s] SP - trim point No. SP = 1 … SG
MA - lower measuring range value [m/s] SG - overall number of trim points
ME - upper measuring range value [m/s] g - distribution coefficient
MB - measuring range [m/s]
4.2.3 MAX-MIN Calibration procedure
The MAX/MIN calibration procedure has been selected because the critical parameter (max. heating
power) is determined in the computer background after the first calibration step (max. flow velocity).
If too high a temperature differential has been selected for the heater control to indicate, this is
displayed as “error 30”. It is then immediately possible to reduce the temperature differential to
a value the controller is able to indicate (see para. 4.2.1, Selection of CTD value).
It is thus verified and ensured when starting the calibration that the flow characteristics can
be displayed, eliminating that a curve must be dropped because its last trim point(s) cannot be
indicated.
AB = MA + (MB x (1 - e
-(((SP-1) x g)/SG)
))
g = 2.5 x (SP - 1)/SG
MB = ME - MA
4.2.2 Trim point selection - number and position
Between 2 and 20 trim points can be set.
They are addressed in a “downward” sequence to ensure the user can recognize the trim points
still available by the trim point index indicated.
A reasonable distribution on the characteristic curve depends on the desired accuracy, the
required measuring range or continuity criteria such as differentiating criteria. These issues are
addressed in section 9.
Generally, there are fewer trim points needed in the upper characteristic curve range than in the
lower range, the reason for this being the flattening characteristic curve (see section 9).
Depending on the medium and the measuring range, it is possible to use different procedures in
selecting the trim points.
A linear preselection of the trim points has been provided for in the FC01-Ex. With the appropriate
number of trim points set, this procedure achieves good results over the entire velocity range
(5 m/s with water, 25 m/s with air).
A trim point distribution which significantly reduces the measuring error when compared to a
linear distribution, can be determined by the following formula (see 9.2 - Example 2).
AB - trim value [m/s] SP - trim point No. SP = 1 … SG
MA - lower measuring range value [m/s] SG - overall number of trim points
ME - upper measuring range value [m/s] g - distribution coefficient
MB - measuring range [m/s]
4.2.3 MAX-MIN Calibration procedure
The MAX/MIN calibration procedure has been selected because the critical parameter (max. heating
power) is determined in the computer background after the first calibration step (max. flow velocity).
If too high a temperature differential has been selected for the heater control to indicate, this is
displayed as “error 30”. It is then immediately possible to reduce the temperature differential to
a value the controller is able to indicate (see para. 4.2.1, Selection of CTD value).
It is thus verified and ensured when starting the calibration that the flow characteristics can
be displayed, eliminating that a curve must be dropped because its last trim point(s) cannot be
indicated.
AB = MA + (MB x (1 - e
-(((SP-1) x g)/SG)
))
g = 2.5 x (SP - 1)/SG
MB = ME - MA