An introduction to SDI-12

What is SDI-12?

SDI-12 is a standardised interface for connecting digital sensors to a master device – typically an SDI-12 compatible data logger, wireless node or computer.

SDI-12 defines both the digital communications and sensor power standards. A key strength of SDI-12 is that it supports the connection of multiple networked sensors to a single input on a master device. SDI-12 is widely employed in environmental data acquisition applications.

How does SDI-12 Work?

SDI-12 Sensors are low power and feature integrated microprocessors that enable them to perform two way communication with an SDI-12 master device. The sensors output readings in a standard SDI-12 format to be sent to the master device. The inclusion of a microprocessor also gives SDI 12 sensors the ability to perform complex internal correction, compensation and averaging algorithms that enhance the quality of the data.

SDI-12 protocol is based on a master-slave configuration in which the master device sends a data request to each of the individually addressed sensors (slaves). This request signal from the master device briefly wakes all sensors and results in a measurement and data sending response from the targeted sensor. When not responding to a master request, all sensors remain in a dormant energy saving state.

SDI-12 interface (Bus)

The SDI-12 Bus features a bidirectional serial data line through which network communication data is passed (using simple ASCII characters). This is accompanied by a ground line – and a 12 volt line, through which sensor power is supplied.

The key benefits of SDI-12

– The ability to use many sensors with just a single master device, reducing project complexity and costs.

– Low power systems that run off battery and are powered via the interface Bus.

– Many parameters can be transmitted over simplified wiring.

– The ability to interchange sensors without reprogramming the partnering data logger.

– No loss of accuracy over large cable runs.

– Enhanced accuracy of data from microprocessor-enabled sensors that can perform complex internal algorithms.


Typical SDI-12 Network Configurations



Learn more about our growing range of SDI-12 enabled instruments

GP2 Advanced data Logger and Controller

PR2 Profile Probe (SDI-12 version)

WET150 SDI-12 Multi-Parameter Soil Sensor