Introduction; Precautions; Sdm-Sio1A Serial Input/Output Module - Campbell SDM-SIO1A Instruction Manual

SDM-SIO1A Serial Input/Output Module

1.

Introduction

2.

Precautions

The SDM-SIO1A Serial Input/Output Module is designed to allow expansion
of the number of serial ports available on a datalogger for communicating with
intelligent sensors or driving external displays.
The SDM-SIO1A is a functional replacement for the SDM-SIO1 interface,
being slightly smaller and having different labeling for some terminals (see
Appendix B, Matching SDM-SIO1A Connections to an SDM-SIO1
more details of the differences).
FIGURE 1-1. SDM-SIO1A Serial Input/Output Module
WARNING: Ensure that the 12V power supply for the module is switched
•
off when connecting the power and ground wires to the SDM-SIO1A.
When making connections to a datalogger, always ensure power to the
datalogger is switched off and connect the ground (G) wire first.
WARNING: The RS-485 0V ground reference connection may be needed
•
to ensure all units are referenced to a common ground voltage. This is
more often needed with long cable runs. It is advisable to check the
difference in ground potential with some caution before connecting any
wires, to ensure the potential differences are reasonably small and
excessive current will not flow between the two ground wires. There is a
current limiting resistor fitted in the RG line in the SDM-SIO1A, but this
will not be adequate in the event of a serious ground fault, for example, the
ground references being 240 V apart due to faulty AC wiring. If a large
potential difference is found, please seek the advice of a qualified
electrician before continuing with the installation
, for
(p. B-1)
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