Introduction - Campbell SDM-IO16 User Manual

SDM-IO16 16 Channel Input/Output
Expansion Module
The SDM-IO16 (see Figure 1) is a synchronously addressed peripheral. It has 16 ports that
can be configured for input or output which expand the number of control ports of the
datalogger. It is fully compatible with Campbell Scientific's CR6, CR800, CR850, CR1000,
CR1000X, CR3000, CR5000 and CR23X dataloggers.

1. Introduction

Figure 1. SDM-IO16 (with mounting brackets)
The SDM-IO16 expands the digital input and/or output capability of Campbell
Scientific dataloggers. It offers similar functionality to the control ports of the
majority of Campbell Scientific dataloggers.
When a port is configured as an input it can measure the logical state of the port,
count pulses, measure the frequency of and determine the duty cycle of signals
applied to the port. In pulse counting mode there is also an option to enable switch
debounce filtering so the unit can accurately count switch closure events. The
SDM-IO16 measures the frequency of signals by measuring the time between
pulses, thereby giving relatively high-resolution measurements even for low
frequency signals.
The module can also be programmed to generate an interrupt signal to the
datalogger when one or more input signals change state.
When configured as an output, each port can be set to 0 or 5 V by the datalogger.
In addition to being able to drive normal logic level inputs, when an output is set
HI a 'boost' circuit allows it to source a current of up to 100 mA, allowing direct
control of low voltage valves, relays etc.
The SDM-IO16 is a synchronously addressed datalogger peripheral. Datalogger
control ports 1, 2 and 3 are used to address the SDM-IO16 and exchange digital
data with it. This module utilizes advanced error checking techniques to ensure
correct transmission of data to and from the module. Up to sixteen SDM-IO16s
may be addressed, making it possible to control a maximum of 256 ports from the
first three datalogger control ports.
1