Vaisala WAC155, User Manual

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The recommended maximum length of the RS-485 line is 1200 m (4000 ft). In practice, the
achievable line length is affected by the electrical noise and the number of transmitters in the
bus. Very long lines may also gather overvoltage transients and surge currents caused by
nearby lightning strikes.
WAC155 has on-board surge protection on the RS-485 line, accomplished with discharge tubes
and transient zener diodes.
Figure 8 Typical WAC155 System
3.5 Powering
The serial wind transmitter WAC155 transmitter accepts 9 ... 31.5 VDC input power. Typical
average power consumption is 120 mW (with WA15 series sensors and powersave mode
activated).
The power line is protected against incorrect polarity and overvoltage transients caused by
nearby lightning strikes. Transient protection is accomplished with discharge tubes, VDRs, and
transient zener diodes.
If you have the revision B of the board (PCB210450B), the
maximum operating voltage is 15.5 V instead of 31.5 V. The component board
differs in size and outlook. See
Service Connector and Jumper Settings
(page 13) .
CAUTION!
3.5.1 Optional Heating Power
WAC155 also provides the sensors with a throughput and control of heating power, which can
be connected if sensor heating is required. The heating power circuit is galvanically isolated
from the operating power circuit.
WAC155 User Guide M210822EN-E
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