Troubleshooting And Maintenance; Troubleshooting; Rs-485 Internal Circuit Diagram - Campbell SDM-SIO1A Instruction Manual

Serial input/output module

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SDM-SIO1A Serial Input/Output Module

Troubleshooting and Maintenance

8.1

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-SIO1A.

If correctly connected, the SDM-SIO1A 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

datalogger. When receiving data, the character "?" will be returned in place of

the expected data whenever a parity, framing, or overrun error is detected.

These errors are only flagged for RS-232/RS-485/RS-422 data coming into the

SDM-SIO1A.

These types of errors are usually caused by a connection issue or sometimes a

mismatch of the interface type, baud rate, or data format (parity, etc.).

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