Transmission Technique; Installation Notes For Rs-485 - SICK DME 3000-2 Betriebsanleitung

DME 3000-2 _ _P
Software 1.1

4.2.7.2 Transmission Technique

The DME 3000 uses RS-485 as transmission technique. This transmission type is the most common
for PROFIBUS. The application range includes all areas in which a high transmission speed and a
simple, inexpensive installation technique are required. A paired, shielded copper cable is used with a
conductor pair.
The RS-485 transmission technique is very simple to operate. The installation of the paired cable does
not require any expertise. The bus structure enables non-reactive linking and delinking of stations and
the step-by-step operation startup of the system. Later developments do not influence the stations that
are already in operation.
The transmission speed is selectable in the range between 9.6 kBit/s and 12 MBit/s. It is selected
uniformly for all equipment on the bus at the operation startup of the system.
Network topology
Medium
Number of stations
Table 1 : Basic features of the RS-485 transmission technique

4.2.7.3 Installation Notes for RS-485

All equipment is connected in a bus structure (line). Up to 32 subscribers (master or slaves) can be
connected with each other.
The bus is terminated at the beginning and end of each segment by an active bus termination. The
two bus terminations must always carry voltage for trouble-free operation.
The bus termination is not implemented internally in the DME 3000-DP. Supply voltage for the bus
termination is available at the bus outlet plug. This 5 V supply voltage is indirect coupled from the
supply voltage of the DME. The 5 V supply voltage can carry a load of 100 mA and be used for optical
coupling modules if required.
Terminator: see accessories.
If more than 32 subscribers exist, repeaters (power amplifiers) must be used to connect the individual
bus segments.
The max. cable length depends on the transmission speed: see Table 2.
The shown cable lengths can be extended by the use of repeaters. We recommend not connecting
more than three repeaters in a series. The DME 3000-DP supports all transmission speeds cited in
Table 2
.
Baud rate (kBit/s)
Range/segment (m)
Table 2 : Ranges dependent on the transmission speed for cable type A
The information about the cable lengths in Table 2 refer to cable type A with the following values:
Characteristic impendence
Distributed capacity
Loop resistance
Diameter of wire
Wire cross section
Table 3: Cable Values
Be careful when connecting subscribers that the data cables do become not twisted. To achieve a
higher degree of trouble-free operation of the system in environments with high electromagnetic
spurious emission (e.g., automobile production), a shielded data cable must be used. The shielding
serves to improve the electromagnetic compatibility (EMC). The braiding shield and – if applicable –
the film shield below it should be connected at both sides and highly conductive via the most
extensive possible area with shield terminal clamps at the protective grounding. Furthermore, make
certain that the data cable is laid separated from all power cables.
Linear bus, active bus termination at both end,
Branch lines are only permitted with baud rates ≤ 1,5 Mbit/s.
Shielded, paired cable, shielding can be eliminated depending on
the ambient conditions (EMC).
32 stations in each segment without repeater.
Expandable up to 127 with repeaters.
9.6 19.2 93.75
1,200 1,200 1,200
135 to 165 Ω
< 30 pF / m
110 Ω / km
0.64 mm
> 0.34 mm²
187.5 500 1500
1,000 400 200
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