Endress+Hauser PROline promag 53 II3G Mise En Service page 37

PROline Promag 53 FOUNDATION Fieldbus
Endress+Hauser
Functional considerations
Using the following procedure the functional considerations checks whether the desired
segment structure meets the basic requirements for transmission to the physical layer
in IEC 61158-2.
Step 1 – compilation of the functional characteristic values of the fieldbus components
• Fieldbus power supply MTL 5995
U = 19 V
S
I = 350 mA
S
2 Ω (source impedance)
R =
Q
• Fieldbus line
Cable type A
44 Ω /km (effective resistance per unit length)
R =
WK
max. permissible cable length L
• Fieldbus device Promag 53
I = 12 mA (basic current)
B
U = 9...32 V (perm. operating voltage)
B
I = 0 mA (fault current)
FDE
I = 0 (< I )
startup B
• Fieldbus device Cerabar S
I = 10.5 mA (basic current)
B
U = 9...32 V (perm. operating voltage)
B
I = 0 mA (fault current)
FDE
I = 0 (< I )
startup B
Step 2 – calculation of cable length and checking of network structure
The maximum cable length is always determined by the type of cable used. The actual
cable length, which is made up of the length of the main cable and the length of the spur
lines, must not exceed this value. The spur lines are also to be checked (refer to
Table 2, Page 11). The following restrictions apply to the specification of the cable
length and network structure:
• Where cable type A is used the cable length L
• Checking the spur line lengths (refer to Table 2, Page 11).
Calculation of actual cable length:
+ Σ L
L = L
SEG main.
= 580 m + 35 m
= 615 m
Checking the conditions
Consideration
L < L
SEG perm.
L < 120 m
spurs
If one of the conditions is not met then the network structure must be revised.
= 1900 m
perm.
perm.
spurs
Condition met?
Yes

Yes


may be max. 1900 m.
15