Yokogawa EXA SC202 2-Wire Conductivity Transmitter/Analyzer - Manual (Page 37)

IM 12D08B02-01E
3-4 Installation and wiring
Figure 3-6. System configuration
3-3. Wiring of sensors
3-3-1. General precautions
Generally, transmission of signals from SC sensors is at a low voltage and current level. Thus a lot of
care must be taken to avoid interference. Before connecting sensor cables to the transmitter make sure
that following conditions are met:
– the sensor cables are not mounted in tracks together with high voltage and or power switching cables
– only standard sensor cables or extension cable are used
– the transmitter is mounted within the distance of the sensor cables (max. 10 m) + up to 50 m WF10
extension cable.
– the setup is kept flexible for easy insertion and retraction of the sensors in the fitting.
3-3-2. Additional precautions for installations in hazardous areas - Intrinsic safe
Make sure that the total of capacitance and inductances connected to the input terminals of the EXA
SC202S do not exceed the limits given in the certificate.
This sets a limit to the cable and extensions used.
– The intrinsic safe version of the EXA 202 instrument can be mounted in Zone 1.
– The sensors can be installed in Zone 0 or Zone 1 if a safety barrier according to the limits given in the
system certificate is used.
– Ensure that the total of capacitance and inductances connected to the terminals of the EXA SC202 do
not exceed the limits given in the certificate of the safety barrier or distributor.
– The cable used should preferably have a BLUE colour or marking on the outside.
– Installation for (sensors in Zone 0 or 1):
Generally, the distributor with input/output isolation has no external earth connection. If there is an
earth connection on the distributor and the external connection of the transmitter is connected to
“protective” earth, the shield of the 2-wire cable may NOT be connected to “protective” earth at the
distributor too.
INPUT OUTPUT/SUPPLY
Safety Barrier
SC202S only
SENSORS
2,5 or 10 m
DISTRIBUTOR
RECORDER
COMPUTER
HAND HELD
COMMUNICATOR
CURRENT OUTPUT
NO MODE YES
ENT >
FAIL HOLD
YES NO ENT
MEASURE
MAN.CAL
DISPLAY
HOLD
YOKOGAWA
MODE
TEMP
AUT.CAL
1 2 1 8 0 100 0
>