Application - ABB RELION REX640 Technical Manual

Basic functions
to the input scaling but there is also a possibility to use up to four different knee
points. To be able to cover a wide range of input units, the input settings used
for scaling are dimensionless. The output range of the mA output is selected with
parameters
points with parameter
knee points , the knee point settings Input knee point 1-4 and Value knee point 1-4
are visible.
Table 104: Analog output modes for the mA outputs
Output mode
Not in use
–20...20 mA
3.15.4

Application

The general function block can be used in REX640 relays that are equipped with an
RTD/analog module.
The function can be applied to various applications, for example, to measure
temperature, pressure or flow.
3.15.4.1 Input scaling
Each mA/RTD input can be scaled linearly by constructing a separate scaling curve
for each input. The curve consists of two points where the x-axis of the curve
illustrates a range selected for the input and the y-axis is the scaled absolute value
of the input. The input scaling is enabled only when mA or resistance input is used.
When the scaling is enabled, the settings
the scaled range. The range of the scaled input is defined with the settings
minimum and Input maximum .
Scaling example 1
The function is used with a Pt100 temperature sensor. Predefined scaling can be
selected when
174
Value maximum and Value minimum and the selected number of knee
Num of knee points . Depending on the amount of Num of
Description
Default selection when the corresponding output is not
used.
Analog output can operate in the range of –20...20 mA.
The output can be used in a narrower range by setting
minimum and Value maximum .
Input mode is set to "Pt100".
Value maximum and Value minimum affect
1MRS759142 F
Value
Input
REX640
Technical Manual