Yokogawa DO202 2-Wire Dissolved Oxygen Analyzer - Manual (Page 63)

Profibus 4-5
IM 12A00A01-61E
4-3. GETTING STArTEd
Profibus is fully dependent upon digital communication protocol (EN 50170 Volume 2 and IEC 61158 for
IS areas, Profibus PA) and differs in operation from the conventional 4 to 20 mA transmission communi-
cation 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 an instru-
ment shop.
4-3-1 Connection of devices
The following instruments are required for use with Profibus devices:
• Power supply:
Profibus requires a dedicated power supply. It is recommended that the 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:
Profibus requires two terminators. Refer to the suppliers manual for details of terminators.
• Field devices / slaves
Several field devices or slave devices can be connected to the same link. depending on the power
consuption, up to 32 devices can be connected. A maximum of 500mA may be used so the theoretical
number of devices is 500mA / Power consumption per device.
• Host / Masters
Used for accessing field devices. A dedicated Master Class 1 host (such as PLC) is used for dedicated
cyclic communication. A master Class 2 Host is used for device management puposes such as changing
the “ device address” or parameter settings. For operation of the host, refer to the instruction manual for
each host. No details of the host are explained in the rest of this material.
• Cable:
Used for connecting devices. Refer to IEC 61158 for details of instrumentation cabling.
Profibus PA uses twisted pair wires up to 1900 metre. To meet the Electro Magnetic Interference
standards a shielded twisted pair is obligated.
For applications in intrinsically safe areas, the transmission method defined in IEC 61158-2 is used with
PROFIUS-PA The transmission rate in this case is 31.25 kbit/s. DP transmission via RS 485 to IEC 61158-2
is implemented with the network components (DP/PA coupler or DP/PA link)
Connect the devices as shown in Figure 4.7. Connect the terminators at both ends of the trunk, with a mini-
mum length of the spur laid for connection.
The polarity of signal and power must be maintained.
EXA
Power
supply
Terminator HOST Coupler/terminator
Figure 4.7 Cabling
NOTE
Before using a Profibus 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.