Vaisala Hydromet Data Collection Platform - Manual (Page 111)

Chapter 3 _____________________________________________ Configuring Modules and Sensors
VAISALA______________________________________________________________________ 109
Physical Interface
The QML logger has five different types of optional serial interfaces
available for the sensor connections.
The serial communications options are listed in Table 9 on page 109 :
Table 9 Serial Communication Options
Interface Communication
Module Application
RS-232 Dual RS-232 module
DSU232
(two RS-232) Distance <20 m
Single sensor
Lowest electrical interference
tolerance
Full duplex communication
RS-485
(4-wire) Isolated RS-485
module DSI485 Distance up to 1500 m
Single sensor
Better interference tolerance
Full duplex communication
RS-485
(2-wire) Dual RS-485
modules DSI485,
DSI486
(two RS-485) Distance up to 1500 m
Several sensors
Better interference tolerance
Half duplex communication
Modem Fixed line modem
module DMX501 Long distances or extreme
interference conditions
SDI Dual RS-485 module
DSI486 SDI sensors
NOTE The recommended connection interface is 2-wire RS-485 with a dual
RS-485 module in the QML logger. This allows an interference-
tolerant connection with the possibility to connect several sensors to
the same serial line.
NOTE Wiring of the data and power lines depends on the application.