User Manual

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Siemens TX-I/O Engineering and installation guide CM110562en_13
Building Technologies Principles of electrical design 2019-05-15
The maximum permissible cable length for passive resistance sensors and transmitters
depends on the permissible measuring error due to the line resistance (see the graphs
below).
The maximum cable length is 300 m.
L
R
L
R
L
BUS
U
B
10762A033
B LG-Ni resistance sensor or resistance transmitter
L Cable length
R
L
Line resistance
U Measured value input of I/O module
The measured value functions are already adjusted with a line resistance of 1 ohm and
the graphs below take account of this.
Exception: the 4-wire signal types Pt100_4 and P100 as well as NTC10K and NTC100K.
The sensor calibration can also be adjusted via software configuration in the auto-
mation station in cases where measuring errors are caused by deviations in the line
resistance or by specific ambient conditions (Intercept in CFC, see section 10.12.2).
The graphs below are for copper cable.
2
1
0
100 200 300
F [K]
L [m]
-0,21
1 mm
²
1,5 mm ²
2,5 mm ²
10762d034
0,6 mm Ø
Formula: F =
4.7
1
A57
L2
−
•
•
A Cable cross-section in mm
2
F Measured temperature error in K
L Cable length in m
Cable length
Key
Line resistance
("Sensor calibration")
Measured value error
LG-Ni 1000
a)
Measured value error
due to line resistance
Key