Rtd/Ma Input/Ma Output Connection - ABB RELION REX640 Technical Manual

Basic functions
Value maximum 20
Value knee point 4
Value knee point 3
Value knee point 2
Value knee point 1
Figure 78: Scaling of AO_VAL to mA output with four knee points
3.15.5

RTD/mA input/mA output connection

RTD inputs can be used with a 2-wire or 3-wire connection with common ground.
When using the 3-wire connection, it is important that all three wires connecting the
sensor are symmetrical, that is, the wires are of the same type and length. Thus the
wire resistance is automatically compensated.
RTD/mA card variants
The available variants of RTD cards are 10RTD/2mA and 3RTD/6mA. The features are
similar in both cards.
10RTD/2mA card
This card accepts two milliampere inputs and ten inputs from the RTD sensors. The
inputs 1 and 2 are used for current measurement, whereas inputs from 3 to 12 are
used for resistance type of measurements.
3RTD/6mA card
This card accepts six milliampere inputs and three inputs from the RTD sensors. The
inputs from 1 to 6 are used for current measurement, whereas inputs from 7 to 9
are used for resistance type of measurements.
180
Output [mA]
19
12
11
5
Value minimum 4
10
Incorrect knee point values against the minimum and
maximum values and a too narrow interval between the
knee point values can cause inaccuracy to the output
scaling function. Use increasing linearity and a value
interval >1.0 for most accurate results.
40 70 100
1MRS759142 F
AO_VAL
130 160
REX640
Technical Manual