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Enabling better global research outcomes in soil, plant & environmental monitoring.

AC-421 SDI-12 to USB Converter

The AC-421 enables easy programming of any SDI-12 sensor by simply connecting the sensor to a computer’s USB port.
Configuration of the sensor can be done using any terminal program or Apogee Instruments DSI software.

One side of the AC-421 features a USB connection for plugging into a computer. The other side of the AC-421 has +12 V out, GND, and SDI-12 data channels for connection to any standard SDI-12 sensor.

  • Easily configure and take sample measurements from any SDI-12 sensor directly with a computer and GUI
  • No data logger needed
  • Growing library of sensors with commands explained
  • Sensor power provided via USB


  • SDI-12 sensor configuration or programming
  • SDI-12 sensor troubleshooting
  • Field use
  • Research applications
  • Classroom labs
Input Voltage Requirement: 5 V USB
Current Draw: 13 mA
Response Time: 0.6 s, time for detector signal to reach 95% following a step change; fastest data transmission rate for SDI-12 circuitry is 1s
Operating Environment: -45 to 80°C; 0 to 100% relative humidity (non-condensing)
Dimensions: 60.40 mm x 17.40 mm x 12.45 mm
Mass: 11 g