Vaisala LT31, Руководство пользователя, Страница: 78 / 294

User's Guide ______________________________________________________________________
78 __________________________________________________________________ M210667EN-C
Communication Options
LT31 provides RS-232, RS-485, and modem transmission interfaces for
data messages. A separate RS-232 interface is provided for maintenance
purposes. Consider your communication needs before the installation.
The method of communication depends on the distance between the host
computer system and LT31. The possibilities are described in Table 8
below.
Table 8 Communication Cable Lengths
Cable Length One LT31 Several LT31 on the line
< 50 m RS-232; RS-485 RS-485; modem (only 300 bps)
< 1200 m RS-485; modem RS-485; modem (only 300 bps)
> 1200 m Modem Modem (only 300 bps)
Serial Communications Settings
NOTE The default serial communications port settings of LT31 are the
following: 9600 bps, no parity, 8 data bits, and 1 stop bit.
Serial Transmission with RS-232
For the RS-232 communication method, connect the signal wires to the
screw terminal at the CPU board LTC212. See Figure 36 on page 79. The
flow control lines RTS and CTS are not required but they can be used.
The hardware flow control can be enabled in LT31. As a default, the RTS
and CTS lines are not used. For details, see Chapter 5, Operation, on
page 145.
NOTE The cable shield of the RS-232 cable must be properly grounded in the
cable gland of the interface enclosure, see Figure 35 on page 77.