Bronkhorst PROFIBUS-DP slave interface - Manual (Page 9)

BRONKHORST ®
2.3 PROFIBUS DP
CABLES
PROFIBUS cables are shielded twisted-pair copper cables which differ from each other in the type of wire
(fixed/flexible) and/or sheath. The two inner cores of a PROFIBUS cable have green and red insulation. The
specifications in this chapter are primarily intended to provide a general introduction and describe the cable
properties to be considered (see also IEC 61784-5-3).
The cables for PROFIBUS DP are assigned to categories, the so-called line types, which define specific physical
parameters. The individual line types are identified by the capital letters A, B, C and D. When planning a network you
should exclusively use line type A.
The table below shows the parameters of line type A that must be complied with.
Parameter Specified limits
Impedance 135..165 Ω with f = 3...20 MHz
Operational capacity ≤ 30 pF/m
Loop resistance ≤110 Ω/km
Wire diameter >0.64 mm
Wire CSA > 0.34 mm2
2.4 M
AXIMAL CABLE LENGTH WITH
PROFIBUS DP
The maximum transmission distance (Trunk Line), that can be achieved using copper cables is directly related to the
transmission speed chosen for the PROFIBUS DP network. As a result, these two variables must always be considered
together. The data transmission rate of PROFIBUS DP is adjustable in defined steps between 9.6 and 12.000 kbits/s.
The data transmission rate must be identical for all segments of a PROFIBUS line. The table below shows the
maximum possible transmission distances that can be reached when using copper cables. The minimal cable distance
between two device connections is one (1) meter.
Transmission rate (kbits/s) maximum Transmission distance* (L
T
) (meter)
9.6 1200
19.2 1200
45.45 1200
93.75 1200
187.5 1000
500 400
1500 200
3000 100
6000 100
12000 100
* Calculated for PROFIBUS cable type A at 30 pF/m
B-coded
4
2
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Page 9 PROFIBUS DP interface 9.17.025