ADS-270 User Guide
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3.7 Wiring the SDI-12 Serial Bus
SDI-12 is an asynchronous, ASCII, serial communications protocol that was
developed for intelligent sensory instruments that typically monitor environmental
data. The communication is achieved by digital communications. The addressing
system allows data recorder to communicate with several microprocessor-based
sensors over a single line.
ADS-200 is compliant to the SDI-12 Standard Version 1.2 and supports extended
commands for sensor configuration, in terminal mode. ADS-200 can collect data from
several SDI-12 sensors for a total amount of 8 measurement channels.
SDI-12 connections:
J5-2:
SDI data line
J4-3:
GND
J4-1:
12V excitation output. The 5V excitation output (
J4-2)
can be used instead, for
sensors with a 5VDC supply option.
It is recommended to read the sensor manufacturers’ Sensor Manual and the SDI-12
Specification by the SDI-12 Support Group
[1]
before utilizing the corresponding
functions of the ADS-270 device.
3.8 Wiring the RS-485 Bus
ADU-500 supports the popular MODBUS protocol over a differential RS-485 bus. The
bus line is internally terminated with a 120
Ω resistor.
