ABB 2600T Pressure Transmitter Series, Руководство пользователя

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364xS User’s Manual 33
Configuration
To avoid the extremely high gain error with the input
approaching zero, the transmitter output is linear with
the input up with a slope of 1 up to 0.5% and then still
linear with the appropriated slope to a programmable
percentage value between 10 % and 20%. This option
is offer in order to ensure a more stable output near
zero. This also allows an easier zero adjustment and
performs a reduced zero error for ambient temperature
variations.
0
5
10
15
20
25
0 1 2 3 4 5 6
%
%
To neglect the values with the input approaching zero,
the transmitter output is zero with the input up to a
programmable percentage value between 0 % and
20%. This option is offer in order to ensure a more
stable flow measure.
This option is possible for all the listed output
functions.
0
5
10
15
20
25
0 1 2 3 4 5 6
%
%
The x
3
Square root Transfer function can be used for
open channel (see figures on the right) flow
measurement using ISO 1438 rectangular weirs
(Hamilton Smith, Kindsvater-Carter, Rehbock
formulas) or trapezoidal weirs (Cippoletti formulas)
and ISO 1438 Venturi flumes. In these types of
devices the relationship between the flow and the
developed head h (the differential pressure mesured
by the transmitter) is proportional to h
3/2
or square root
of h
3
. Other types of Venturi or Parshall flume do not
follow this relationship.
Using this function, the output (in % of the span) is
proportional to the square root of the third power of the
input signal in % of the calibrated span: the instrument
gives an output proportional to the rate of flow
calculated using the above mentioned formulas.
The x
5
Square root Transfer function can be used for
open channel flow measurement using ISO 1438 V-
notch (triangular) weirs (see figure on the right) where
the relationship between the flow and the developed
head h (the differential pressure measured by the
transmitter) is proportional to h
5/2
or square root of h
5
.
Using this function, the output (in % of the span) is
proportional to the square root of the fifth power of the
input signal in % of the calibrated span: the instrument
(it gives an output proportional to the rate of flow
calculated using the Kingsvater-Shen formula).
Slope = 1
programmable
percentage value
Theoretical Square
Root Curve
programmable
percentage value
Theoretical Square
Root Curve