Connect Wiring And Power Up; Signal Cable; Signal Cable Length; Transmitter Cable - Emerson Rosemount 520 Quick Start Manual

February 2019

4.0 Connect wiring and power up

4.1 Signal cable

Shielded twisted pair cable should be used for best result. Use wire with minimum
diameter of 0.51 mm (24 AWG). To ensure the functionality of the digital
communication the following table shall be used to determine the maximum

signal cable length:

Table 4. Signal Cable Length
Transmitter cable length

0 m < x
25 m < x

50 m < x
100 m < x
200 m < x
Note
The calculated signal cable lengths are based on a conventionally constructed

cable with a capacitance equal to or less than 200 pF/m.
Maximum allowed transmitter cable length for installation in hazardous area is

75 m. Maximum allowed total cable length, transmitter cable plus signal
cable, must be determined by IS loop calculations.

4.2 Transmitter cable

The vent tube must be directed to an area with atmospheric pressure. If the
transmitter cable terminates in an area with overpressure or negative pressure
relative to the atmospheric pressure in the tank, the vent tube must be directed
to an area with atmospheric pressure equal to the pressure inside the tank.
4.3 Power supply
The power supply and load limitations are described in
resistance load is the sum of the resistance of the signal cable and the load
resistance of the controller, indicator, and related equipment. Note that the
resistance of intrinsic safety barriers, if used, must be included.
Signal cable maximum length
25 m

50 m
100 m

200 m

300 m
825 m
770 m
660 m
440 m
220 m
Quick Start Guide
Figure 8 below. The total
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