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SDAO 2 Channel Analog Output Smart Card

This product has been discontinued. This web page is provided so current customers using the product can have a quick reference for specifications. Please contact Automation Electronics for current products that may meet your needs.

2 channel D/A smart card2 Channel Analog Output Smart Card

The Automation and Electronics, Inc. SDAO was designed to provide analog output expansion capability for Programmable Logic Controllers (PLCs). With a low power requirement and a wide operating temperature range, the SDAO is ideal for use in remote 120 VAC, 24 VDC, or solar powered distributed I/O systems. It can also be used as a stand-alone MODBUS analog output module.

The SDAO is a microprocessor based 2 channel 4-20 mA analog output board. The outputs can be used in remote or local power mode. In remote power mode, the 4-20 mA loop power is provided externally. In local power mode, the SDAO provides the 24 VDC loop power. On-board jumpers configure the output types. The on-board microprocessor controls the analog outputs on this board from communicated values from host systems or master controllers via a serial data highway.

The data highway is implemented using the built in RS-485 serial port. All of the Smart Card series can be daisy chained together using these serial ports. Each Smart Card responds to MODBUS polls or commands from a master. An on-board address selector switch allows each board to be easily configured for any MODBUS address. This RS-485 data highway can then be used to create a scalable, flexible input / output expansion array.


  • Analog output value backup (24 hour via on-board capacitor)
  • MODBUS RTU protocol
  • On-board address switch (0-255)
  • Four on-board option switches
  • Two RJ45 jacks for RS-485 serial data
  • Selectable RS-485 termination
  • Expansion connector for our P-type piggyback modules


Size: 4-1/2" x 6-3/8" PC board
Mounting: Snap track
Operating temperature: -40 to +158 deg. F (-40 to +70 deg. C)
Relative humidity: 5 to 90% non-condensing
Power requirements
Typical: Processor - Less than 50 mA @ 10 to 30 VDC
CPU / Memory
CPU: 68HC11
Memory: 128 kB flash, 32 kB EEPROM, 2 kB RAM
Output configuration
Standard: Two analog outputs; 0-20 mA or 4-20 mA 16 bit conversion; 0.15% maximum error; RLoad 100 Ohm min; ((VL-3)/.02) max
Loop power: 12 to 30 VDC
RS-485: 9,600 baud; two RJ45 connectors
Protocols: MODBUS RTU protocol