Digital Inputs; Passive Resistance Sensors And Resistance Transmitters - Siemens Desigo TRA Engineering, Mounting And Installation Manual

Common conductor
with multiple contacts
Connection diagram
(Example)
Line resistance
Key
34 / 84
Siemens
Building Technologies
7.1.1

Digital inputs

When several status or counter contacts are to be connected, a common
conductor may be used. This saves wiring.
However, system ground must be connected at least once per room automation
station / per TX-I/O module.
U1
(1) (2) (3)
1 2 3 4 5 6 7
In principle, the number of contacts that can be connected via a common
conductor depends on the length and cross section of the conductor.
However, the measuring current (1...2 mA) is so small that up to 16 inputs
(TXM1.16D) can be connected with the minimum cross section 0.28 mm
(0.6 mm diameter) and with the maximum cable length of 300 m / 1000 ft.
7.1.2

Passive resistance sensors and resistance transmitters

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 / 1000 ft for TX-I/O and 80m / 260 ft for DXR2.
R
L
B
R
L
L
B LG-Ni resistance sensor or resistance transmitter
L Cable length
R Line resistance
L
U Measured value input of I/O module
Desigo TRA Engineering, mounting and installation
Wiring of field devices (without bus)
(4) (5)
8 9 10
2
BUS
U
CM111043en_09
2016-02-22