Campbell Scientific SDM-IO16 16-Channel Input/Output Expansion Module - Manual (Page 7)

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 CR800, CR850, CR1000,
CR3000, CR5000, CR10X, and CR23X dataloggers.
FIGURE 1. SDM-IO16 (with mounting brackets)
1. Introduction
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
1