SDM-SIO4A 4-Channel Serial I/O Interface

The SDM-SIO4A is a 4-channel serial I/O expansion module for Campbell Scientific dataloggers.

It is designed to add 4 x additional and individually configurable and addressable RS-232, RS-422, or RS-485 (half- or full-duplex) serial ports to an SDM-capable datalogger for the purposes of interfacing with intelligent sensors, actuators, or displays. Up to three SDM-SIO4A modules can be connected to a single datalogger SDM port. The SDM-SIO4A channels behave much like a native datalogger serial port and use the same familiar serial I/O commands. The SDM-SIO4A is transient and surge protected to IEC61000-4-5 level 4 on the serial port interfaces, avoiding the need for separate transient protection in most applications.

Note: The SDM-SIO4A is not a direct replacement for the SDM-SIO4 which is no longer available. The SDM-SIO4A consists of four SDM-SIO1A modules in a single package. Consequently, the SDM-SIO4A is a good replacement for up to four SDM-SIO1 modules or as an alternative to the SDM-SIO1A.



  • Add up to 12 serial sensors to a compatible datalogger
  • Fully compliant with the RS-232, RS-422, and RS-485 (half- and full-duplex) standards
  • Can buffer large amounts of data between processing
  • Supports terminal "talk-through" mode for testing and diagnostics


Key Specifications

  • Data rates: 300, 1200, 2400, 4800, 9600, 19200, 38400, 57600, and 115200 bits/s. Autobaud NOT supported.
  • Supported modes: RS-232 (full duplex and receive only); RS-485 (half and full duplex); RS-422 (half and full duplex); Hardware CTS/RTS flow control is supported in RS-232 mode. The handshaking lines can also be used as general purpose I/O lines.
  • Compatible dataloggers (using SDM): CR800-series, CR1000, CR3000, CR9000X (OS>6), CR6. The CR10X and other Edlog dataloggers are NOT compatible.


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