Figure 3-3: Example of Installation on Two Tanks
A. Rosemount 2410 Tank Hub
B. Tankbus
C. 300 m
D. Voltage drop=0.80 V
E. (Spur < 60 m)
F. Rosemount 5408 Level Transmitter
G. Rosemount 644 Temperature Transmitter
H. Segment coupler
I. 350 m
J. Voltage drop=0.47 V
The total operating current of the connected field devices on the two tanks is 32+32
mA=64 mA. This is within the output capability of the Rosemount 2410 Tank Hub.
Calculations
The tank hub is powered by an intrinsically safe power supply: 12.5 V, 250 mA.
Voltage drop to the first tank: 64 mA x 0.30 km x 42 Ω/km=0.80 V.
Voltage at first tank =12.5 V - 0.80 V=11.70 V.
Voltage drop between first and second tank: 32 mA x 0.35 km x 42 Ω/km=0.47 V.
Voltage at second tank =12.5 V - 0.80 V - 0.47 V=11.23 V.
For both tanks the input voltage to the field devices is above the minimum requirement of
9 V.
The field devices may be connected to the Tankbus via segment couplers as illustrated in
Figure 3-3. The spur length must not exceed 60 m according to the FISCO standard. In the
example above, it is assumed that the voltage drop between the segment coupler and the
devices can be ignored.
Related information
Power budget
Installation
Reference Manual
December 2019 00809-0100-2410
38 Reference Manual
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