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LevelPRO -
Multiple Tank Level Processor
EX-1803
Communications Interface -
Network Systems
Network Communications (RS-485)
LevelPRO tank processors can provide direct ASCII
communications via a two wire multi-drop network
interface. Recommended communications cable is
Belden 9501 (24 AWG twisted pair stranded conductors,
copper drain wire, overall shielding).
Connections are provided on the plug in terminal for A,
B and SH (shield). Refer to the RS-485 diagram for
proper cabling connections. Up to 32 individual
LevelPRO devices can be installed on a multi-drop
network.
Preliminary Network Communications
Troubleshooting
These are only a few possible causes of communications
problems. Also, consult available reference materials for
the host or receiver (i.e., PLC or PC) that is being used to
communicate with the LevelPRO devices.
No Communications
Loss of communications to all devices in the network.
• Check connections at RS-485 terminals at each
device. If one processor has been disconnected from
the network, make certain that cabling has continuity.
• Check that power is being supplied to the LevelPRO
processors. There will be no communications if
individual devices suffer loss of power.
No Communications Response (Individual)
Failure of queried polling address device to respond with
communications
• Check that power is supplied to the LevelPRO
processor. Additionally, check internal power supply
fuse, replace if necessary.
• Check communications connections at RS-485
terminals. If cable conductors have been reversed,
unit will not be able to communicate. Make certain
that A, B, SHD (shield) continuity has been
maintained.
• Possible incorrect polling address. 3-digit ASCII
address value must correspond to polling address
programmed in datapack (SRAM) of LevelPRO.
A
B GND
A
B GND
A
B GND
LevelPRO
LevelPRO
Host
Detail
- RS-485 diagram
1 2 3 4 5 6 7 8 9
Shield (Drain Wire)
B (Black Wire)
A (Red Wire)
