XLINK 500/100 Operations & Maintenance Manual page # 25
4.6.
Connecting RS-485 Sensors
The RS-485 bus may be used to collect data from sensors. Alternatively, it may be used to have a
Modbus master collect data from the station.
RS-485 sensors that use the SDI-12 protocol for its messaging are supported.
Collecting data using the Modbus protocol over RS-485 is supported
Multiple devices may be attached on the RS-485 bus; each of those devices must have a
different address.
It is OK to mix SDI-12 and Modbus sensors on the RS-485 bus.
Wiring RS-485 involves two lines: RS-485 A and RS-485 B.
Note: if there is an issue talking to a sensor over RS-485, try reversing the A and B wires. If a
Modbus sensor is not responding, make sure that the Modbus communications settings in XLink
match the sensor settings.
4.7.
Connecting Tipping Bucket Rain Gauge
A tipping bucket rain gauge is supported via the TB/DIN#2 connection. This connection provides
a pull-up resistor (100K) to 3.3V to provide power for the contact switch in the rain gauge. Each
time the bucket in the rain gauge “tips” the internal switch closes momentarily causing a pulse
on the TB/DIN#2 connection. This pulse is counted and used to provide accumulated
precipitation or precipitation rate data.
