SDI-12 integrates METER sensors with data loggers manufactured by other companies such as Campbell Scientific and allows monitoring of up to 62 SDI-12 enabled sensors on each port of a 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 is the correct hardware needed for the system to work properly, an adequate number of well-trained technicians is also required to monitor the system and ensure that it transmits data properly throughout a study. For more technical information on SDI-12, visit 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 there’s no time to check a system frequently, do not use SDI-12.
- The study could not tolerate a gap in data transmission. The nature of SDI-12 makes data outages inevitable. If a study can’t tolerate occasional loss of data, use a different system setup.
- The research team did not include skilled technical personnel. SDI-12 systems will experience failures. If there’s no available expertise to solve these issues in-house, SDI-12 will be frustrating.
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. METER and many other manufacturers have SDI-12-compatible sensors. At METER, each of our digital sensors, including the 5TM, 5TE, and TEROS 21 are SDI-12 compatible. For more information on our SDI-12 compatible sensors and their capabilities, visit the sensors page.
Keep in mind that SDI-12 requires a three-wire interface:
- Serial data line
- Ground line
- 12-volt line
To meet this need when ordering from METER, 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.
SDI-12 requires a logger that can have a two-way conversation with a sensor. METER does not manufacture SDI-12 compatible loggers but recommends using data loggers manufactured by Campbell Scientific. METER 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 readout and storage device, is meant to be an all-in-one SDI-12 sidekick. The ProCheck makes addressing sensors during setup and troubleshooting an SDI-12 system 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. The ProCheck isn’t absolutely required to address and troubleshoot, but it makes things much easier.
Watch a virtual seminar covering the advantages and disadvantages of SDI-12. View it before ordering anything to make absolutely sure that the research application is compatible with SDI-12. For questions after watching the seminar, contact METER support at firstname.lastname@example.org.