Active Sensors And Actuators Dc 0 - Siemens Desigo TRA Engineering, Mounting And Installation Manual

Notes
Caution!
PXC3 with
TX-I/O modules
Cable length for
devices with AC 24 V
Note
Siemens
Building Technologies
7.1.3 Active sensors and actuators DC 0 ... 10 V
The permissible length of DC 10 V cables for signals, and of the cables to supply
the devices, have to be calculated on the following basis for each device (see also
the relevant device data sheets):
– Max. 7 % voltage drop (1.68 V) on the cables due to the sensor supply current.
Reason: to ensure sufficient voltage for the device supply.
– Active sensors: Measuring error of max. 0.5 % due to line resistance on the
measuring conductor (not critical, as the measuring current is only 0.1 mA)
– Active actuators: control signal error of max. 1 % due to line resistance on the
measuring conductor (not critical, as the measuring current is only 0.1 mA)
Longer cables are permissible provided larger measuring errors are acceptable.
If the device is supplied locally from a transformer, the signal cable can be up to
300 m / 1000 ft long (DXR2: 80 m / 260 ft) with a wire diameter of
The local transformer MUST NOT be earthed (earth loop)!
DC 0...10 V actuators with DC 0...10 V feedback:
System neutral of output and feedback may be in the same conductor due to the
small current. However, output and feedback must be on the same device.
In case of active sensors with AC 24 V supply, use cable cross section suited for
10 A according to local regulations (T 10 A fuse in the power supply module /
room automation station).
The maximum cable length is 300 m / 1000 ft (DXR2: 80 m / 260 ft).
The permissible length of the cables is calculated as follows: Voltage drop of max.
7 % (1.68 V) on the AC 24 V operating voltage for the sensor / actuator.
Cable cross section
Power
2
/ AWG14
2.50 mm
2
/ AWG16
1.50 mm
2
/ AWG18
1.00 mm
2
/ AWG20
0.75 mm
The outgoing and return cables may each have the indicated length.
Desigo TRA Engineering, mounting and installation
Wiring of field devices (without bus)
Cable length
2 VA 5 VA 10 VA
300 m 300 m 235 m
1000 ft 1000 ft 770 ft
300 m 300 m 150 m
1000 ft 1000 ft 500 ft
300 m 185 m
1000 ft 600 ft 300 ft
290 m 120 m
960 ft 380 ft 190 ft
0.6 mm.
20 VA 50 VA
120 m
390 ft 150 ft
75 m
250 ft 100 ft
95 m 50 m
150 ft
60 m 30 m
95 ft
CM111043en_09
2016-02-22
47 m
30 m
20 m
60 ft
12 m
40 ft
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