ABB LevelMaster 7100, Руководство пользователя, Страница: 37 / 100

LevelMaster 7100 User manual 2105835 Rev AA | 27
Figure 23: General schematic of a multi-LevelMaster bus (general purpose location)
Limitations
The number of units that can be supported per bus, and the length of the bus, depends on the type of location and installation
scenario. Table 5 describes the maximum bus length and the maximum number of units for each scenario.
IMPORTANT NOTES: It is assumed that the wires for both communication and power will be run through the
conduits and that the wire length conforms to the specified limits. Wire length limits vary depending on the
installation scenario.
Connecting multiple LevelMasters requires wiring more than one wire at the same contact point in the power or
communication connectors. Review section 4.2,
Selecting wire type , to ensure that the correct wire type and gauge
has been selected.
Table 5: Wiring limits on the RS-485 bus
Installation scenario Description
Maximum bus length
(total wire length in feet)
Maximum number of LevelMasters
on the bus
General-purpose
(unclassified area) with host
controller
Direct connection to host
controller. No barrier required
4000 8
Hazardous location
(classified area) with host
controller
No direct connection to host
controller.
CSA-certified barrier required
between first LevelMaster on
the bus and host controller
500
Group D:4 sensors per barrier
Group C,D: 3 sensors per barrier
Wiring for communication
To wire the additional LevelMaster(s) for communication:
1. Remove the communication 4-position terminal connector from the port (J11) on the additional LevelMaster.
2. Loosen the screws on the communication connector.
3. Insert the wires in the correct position (see Figure 24, Figure 25, Figure 26, or Figure 27 for sample wiring):
a. If the additional LevelMaster is the last unit on the bus, insert the wires from the first LevelMaster in the outer (T+, T-)
pair (first and fourth pin on J11). Secure the inserted wires by tightening the screws on the connector.
b. If the additional LevelMaster is an intermediate unit on the bus:
i. Insert the wires from the first LevelMaster in the outer (T+, T-) pair, first and fourth pin on J11.
ii. Insert the wires to the next LevelMaster in the inner (T+, T-) pair, second and third pin on J11.
iii. Secure the inserted wires by tightening the screws on the connector.