Figure 7-1. RS-485 internal circuit diagram
RG is for connecting the screen/ground of the data lines when in RS-485 mode; there is a 1 W
100 Ω resistor in series designed to limit any currents that may be induced due to a difference in
ground potentials between the sensor and the SDM-SIO2R.
8. Troubleshooting and
maintenance
8.1 Troubleshooting
If correctly connected, the SDM-SIO2R normally operates seamlessly. However, there are some
common issues people encounter during setup or sometimes after a period of operation.
During the setup phase, either no data or corrupt data may be received by the data logger. When
receiving data, the character “?” will be returned in place of the expected data whenever a parity,
SDM-SIO2R Serial Input/Output Module with Switched Sensor Power
37
