Yokogawa RotaMASS 3-Series User Manual

Page 84

9. EXPLOSION PrOTECTEd TyPE INSTrUMENTS

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IM 01R04B05-00E-E 3rd edition July 30, 2010 -00

Supposable Bus Cable

the cable used to interconnect the FF-devices needs to comply with the following parameters:

loop resistance R’: 15...150 Ω/km
inductance per unit length Lc: 0.4...1 mH/km
capacitance per unit length Cc: 80...200 nF/km
C’ = C’ line/line + 0.5 C’ line/screen, if both lines are floating
or
C’ = C’ line/line + C’ line/screen, if the screen is connected to one line
length of spur cable: max. 30 m (IIC and IIB )
length of trunk cable: max. 1 km (IIC) or 5 km (IIB)

Terminators

the terminator must be certified by a notified body as FISCo model and at each end of the trunk cable an
approved line terminator with the following parameters is suitable:

R = 90...100 Ω
C = 0...2.2 µF (0.8 ... 1.2 µF is required in operation)
the resistor must be infallible according to IEC 60079-11.

Number of devices

the number of devices (max. 32) possible on a fieldbus link depends on factors such as the power con-
sumption of each device, the type of cable used, use of repeaters, etc.