Yokogawa EXA PH202 2-Wire pH/ORP Analyzer - Manual (Page 30)

IM 12B07D02-01E
Specification 2-17
x In each I.S. Fieldbus segment only one active source, normally the FM Approved FISCO
barrier, is allowed to provide the necessary power for the Fieldbus system. All other
equipment connected to the bus cable has to be passive (not providing energy to the
system), except to a leakage current of 50μA for each connected device. Seperately
powered equipment needs a galvanic isolation to insure that the I.S. Fieldbus circuit
remains passive.
x The cable used to interconnect the devices needs to comply with the following
parameters:
Loop resistance R’: 15 … 150 Ω/km; Inductance per unit length L’: 0,4 … 1 mH/km
Capacitance per unit length C’: 80 … 200 nF/km
(C’ = C’ line/line + 0,5 C’ line/screen if both line are floating)
(C’ = C’ line/line + C’ line/screen if the screen is connected to one line)
Length of spur cable: max. 30 m
Length of trunk cable: max. 1 km
Length of splice : max. 1 m
WARNING
- Substitution of components may impair Intrinsic Safety
- To prevent ignition of flammable or combustible atmospheres, disconnect power
before servicing or read, understand and adhere to the manufacturer’s live
maintenance procedures.
Application Doc. No.: IKE025-A10 P.6 to P.7