Vaisala WXT520 - Manual (Page 159)

Appendix B __________________________________________________________ SDI-12 Protocol
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APPENDIX B
SDI-12 PROTOCOL
SDI-12 is a standard for interfacing data recorders with microprocessor-
based sensors. The name stands for serial/digital interface at 1200 baud.
More information of the complete SDI-12 standard text is available
from the SDI-12 web-site in the following address:
www.sdi-12.org .
SDI-12 Electrical Interface
The SDI-12 electrical interface uses the SDI-12 bus to transmit serial
data between SDI-12 data recorders and sensors. The SDI-12 bus is the
cable that connects multiple SDI-12 devices. This is a cable with three
conductors:
- a serial data line,
- a ground line, and
- a 12-volt line.
The SDI-12 bus can have at least 10 sensors connected to it. The bus
topology is a parallel connection, where each of the three wires of
different sensors are connected in parallel.