35
Reference Manual
00809-0100-2240, Rev DA
October 2017
Shield wire ground
To protect the fieldbus segment (Tankbus) from noise, grounding techniques for shield wire usually
require a single grounding point to avoid creating a ground loop. The ground point is typically at the
power supply.
In the Rosemount Tank Gauging system, a ground point is located at the Rosemount 2410 Tank Hub
which acts as the power supply for devices on the Tankbus.
The Rosemount Tank Gauging devices are designed for “daisy-chain” connection of shield wiring in order
to enable a continuous shield throughout the Tankbus network.
The shield loop-through terminal in the Rosemount 2240S is not connected to ground in order to
provide electrical continuity to “daisy-chained” Tankbus cables.
4.4.4
Cable selection
Use shielded twisted pair wiring for the Rosemount 2240S in order to comply with FISCO
(1)
requirements
and EMC regulations. The preferred cable is referred to as type “A” fieldbus cable. The cables must be
suitable for the supply voltage and approved for use in hazardous areas, where applicable. In the U.S.
explosion-proof conduits may be used in the vicinity of the vessel.
Use 22 AWG to 16 AWG (0.5 to1.5 mm²) in order to minimize the voltage drop to the transmitter.
The FISCO specification requires that cables comply with the following parameters:
Table 4-1. FISCO Cable Parameters
1,
See IEC 61158-2 and IEC/TS 60079-27:2002.
Parameter
Value
Loop resistance
15 to 150
/km
Loop inductance
0.4 to 1 mH/km
Capacitance per unit length
45 to 200 nF/km
Maximum length of each spur cable
60 m in gas Groups IIC and IIB
Maximum length of each trunk cable
1 km in gas Group IIC and 1.9 km in
gas Group IIB
Summary of Contents for Rosemount 2240S
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