Chapter 5 _______________________________________________ Wiring and Power Management
VAISALA_______________________________________________________________________ 43
Internal Wiring
The 8-pin M12 connector is wired for RS-232, SDI-12, and RS-485
modes by default. The 4-wire RS-422 requires a different internal
wiring (see also Table 1 on page 42). Refer to the figure below if you
need to change the wiring of the M12 connector.
0505-205
Figure 22 Internal Wiring
The RS-232 interface can be accessed through the M12 connector using
a standard PC serial port. Same applies to the SDI-12 interface, since the
Rx and Tx lines are separate at the M12 connector.
Bidirectional use of the RS-485 and RS-422 interface requires a proper
adapter module between the PC and the WMT52. For testing purposes,
the inverted output of either interface (screw terminal pin #3 TX-) is
directly readable with PC's Received Data line. In this case Signal
Ground for PC ComPort is taken from screw terminal pin #6 SGND (for
testing purposes pin #19 VIN- will also do).
For configuration work, the Service Port is most practical, since it has
constant and convenient line parameters: RS232/19200, 8, N, 1. See
Chapter 6, Connection Options, on page 51 and Figure 3 on page 18.
NOTE
The true SDI-12 line requires that the Rx and Tx wires are joined
together (outside the WMT52). See the interface diagrams in the next
section.
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