Yokogawa EJA115 - Manual (Page 19)

IM 01C22T02-01E 4-1
4. GETTING STARTED
4. GETTING STARTED
Fieldbus is fully dependent upon digital communica-
tion protocol and differs in operation from conven-
tional 4 to 20 mA transmission and the BRAIN
communication protocol. It is recommended that
novice users use field devices in accordance with the
procedures described in this section. The procedures
assume that field devices will be set up on a bench or
in an instrument shop.
4.1 Connection of Devices
The following instruments are required for use with
Fieldbus devices:
• Power supply:
Fieldbus requires a dedicated power supply. It is
recommended that current capacity be well over the
total value of the maximum current consumed by all
devices (including the host). Conventional DC
current cannot be used as is.
• Terminator:
Fieldbus requires two terminators. Refer to the
supplier for details of terminators that are attached
to the host.
• Field devices:
Connect Fieldbus communication type EJA. Two or
more EJA devices or other devices can be con-
nected.
• Host:
Used for accessing field devices. A dedicated host
(such as DCS) is used for an instrumentation line
while dedicated communication tools are used for
experimental purposes. For operation of the host,
refer to the instruction manual for each host. No
other details on the host are given in this material.
• Cable:
Used for connecting devices. Refer to “Fieldbus
Technical Information” (TI 38K03A01-01E) for
details of instrumentation cabling. For laboratory or
other experimental use, a twisted pair cable two to
three meters in length with a cross section of 0.9
mm
2 or more and a cycle period of within 5 cm
(2 inches) may be used. Termination processing
depends on the type of device being deployed. For
EJA, use an M4 screw terminal claw. Some hosts
require a connector.
Refer to Yokogawa when making arrangements to
purchase the recommended equipment.
Connect the devices as shown in Figure 4.1. Connect
the terminators at both ends of the trunk, with a
minimum length of the spur laid for connection.
The polarity of signal and power must be maintained.
EJA
Fieldbus power
supply
Terminator
Terminator
HOST
F0401.EPS
Figure 4.1 Cabling
NOTE
No CHECK terminal is used for Fieldbus com-
munication EJA. Do not connect the field indica-
tor and check meter.
Before using a Fieldbus configuration tool other than
the existing host, confirm it does not affect the loop
functionality in which all devices are already installed
in operation. Disconnect the relevant control loop from
the bus if necessary.
IMPORTANT
Connecting a Fieldbus configuration tool to a
loop with its existing host may cause communi-
cation data scrambling resulting in a functional
disorder or a system failure.