When It Works

SDI-12 lets you integrate Decagon sensors with data loggers manufactured by other companies such as Campbell Scientific, and allows you to monitor up to 62 SDI-12 enabled sensors on each port of your data logger. However, SDI-12 has significant drawbacks. Before committing to an SDI-12 system, fully explore all the pros and cons.

Monitoring 62 sensors on a single data logger port may sound like a dream come true, but for the poorly-informed, the dream can become a nightmare.  Not only do you need the correct hardware for the system to work properly, you also need an adequate number of well-trained technicians to monitor the system and ensure that it transmits data properly throughout your study. For more technical information on SDI-12, visit the homepage of the SDI-12 Support Group.

When SDI-12 Doesn’t Work

Sometimes, SDI-12 literally ruins a research study. The three most common reasons for failure are:

  • The researcher/research staff were unable to visit the site on at least a weekly basis. SDI-12 systems demand constant attention. If you don’t have time to check your system frequently, you should not use SDI-12.

  • The study could not tolerate a gap in data transmission. The nature of SDI-12 makes data outages inevitable. If you can’t tolerate occasional loss of data, you should use a different system setup.

  • The research team did not include skilled technical personnel. SDI-12 systems will experience failures.  If you do not have the expertise to solve these issues in-house, you will experience considerable frustration with your SDI-12 system.

If you know that your research is at risk for one or more of these failure scenarios, STOP. Do not use SDI-12. Check Decagon.com for data collection systems that may better fit your research.

Sensors

Traditional sensor-to-logger communication is  based on one-way communication with data flowing from the sensor to the logger.  In SDI-12, however, the logger queries a particular sensor address, much like calling someone by name before directing a question at them, and the correct sensor responds with data.  Decagon and many other manufacturers  have SDI-12 compatible sensors. At Decagon, each of our digital sensors, including the 5TM, 5TE, GS3, and MPS-2, are SDI-12 compatible. Several soon-to-be-released sensors will also have SDI-12 capability. For more information on our SDI-12 compatible sensors and their capabilities, visit the sensors page.

Keep in mind that SDI-12 requires a 3-wire interface:

  1. Serial data line

  2. Ground line

  3. 12-volt line

To meet this need when ordering from Decagon, ask for “pigtail end” cables on your sensors. If you already have “stereo end” cabled sensors a “pigtail” adapter can convert the sensors for SDI-12 use. You can also hook these adapters into an SDI-12 bus as “stereo ports” for your sensors. For more information on SDI-12 buses, see the Building a Bus page.

Loggers

In order to utilize SDI-12, you must have a logger that can have a two-way conversation with a sensor. Although Decagon itself does not manufacture SDI-12 compatible loggers, we recommend using data loggers manufactured by our sister company, Campbell Scientific. Decagon offers free example programs written specifically for Campbell Scientific loggers. These programs can be found on the example programs page.

The ProCheck: A Necessary Tool

The ProCheck, a sensor read-out and storage device, is meant to be your all-in-one SDI-12 sidekick.  The ProCheck makes addressing  sensors during setup and  troubleshooting your SDI-12 system when problems crop up a breeze. It turns a daunting task involving complicated and temperamental terminal programs into a simple matter of plugging in the sensor and pressing a button or two. You don’t absolutely need the ProCheck to address and troubleshoot, but then again, you don’t absolutely need to wear a seat belt in your car either.

Virtual Seminar

Chris Chambers, Decagon’s customer support scientist, gave a virtual seminar covering the advantages and disadvantages of SDI-12. It is a must watch for anyone planning to implement SDI-12. View it before ordering anything to make absolutely sure that your application is compatible with SDI-12. If you have more questions after watching the seminar, you can email Chris at support@decagon.com.