Vaisala WAC155 - Manual (Page 23)

Chapter 3 _______________________________________________________________ Installation
VAISALA _______________________________________________________________________ 21
Each device in the same bus has a unique configurable ID, containing
1..5 characters. Alphabetical characters a-z and A-Z (case-sensitive) are
accepted, as well as numbers 0-9.
Typically, only a 4-wire shielded cable is required for the line between
the WAC155 transmitter and the receiving end. Two of the four wires
provide the operating power for the system. A twisted pair can be used
for the power wires to reduce interference. The other two wires are for
the RS-485 serial bus connection from the WAC155 transmitter.
The maximum length of an unisolated RS-485 line is 1200m (4000ft).
The cable used should be at least a twisted pair AWG 24 cable. The
achievable line length is affected by electrical noise and the number of
transmitters on the bus.
0702-002 Figure 9 Typical System with 12 VDC Power Supply
Powering
The WAC155 transmitter accepts 9 ... 15.5 VDC as input power.
The power line is protected against incorrect polarity. Transient
protection is accomplished with VDRs, series inductors and resistors,
and transient zener diodes on both the power line and each I/O line.