Solinst AquaVent SDI-12, User Manual

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SDI-12 User Guide for AquaVent
Page 5
1 Introduction
SDI-12 (Serial Data Interface at 1200 Baud) is a communications protocol
designed to allow the interfacing of a number of low power analog sensors with
a common SDI-12 recorder or datalogger (master). The current AquaVent 5
and previous AquaVent loggers are able to act as an SDI-12 Sensor in an
SDI-12 network simply by using the AquaVent 5 SPX Wellhead or
AquaVent SPX Wellhead, and SDI-12 Connector Cable.
Note: As features differ slightly between models, it is recommended to use
the AquaVent 5 SPX Wellhead with an AquaVent 5 logger.
The SPX Wellhead (translator) converts SDI-12 commands to the Solinst
communications protocol for the AquaVent. The SPX Wellhead and SDI-12
Connector Cable provide a hardware and protocol conversion interface between
a Solinst AquaVent and an SDI-12 network.
1.1 SDI-12 Interface
Solinst 2-wire signals are converted to SDI-12 signals by the SPX Wellhead.
The SDI-12 Connector Cable, plugged into the side of this Wellhead, has
three wires which connect to an SDI-12 master. These wires are colour-coded
according to Table 1-1.
The bottom of the Wellhead connects to an AquaVent logger through a Vented
Cable. The AquaVent logger contains a small battery, used only for memory and
clock back-up. The Wellhead contains four user-replaceable 1.5 V AA lithium
batteries that power the AquaVent logger.
The SDI-12 interface circuitry requires the +12V connection to be powered by
customer equipment. The current draw from the 12 volt source normally peaks
at several 10’s of mA, but idles around 30 uA. Upon initial power-up, or after
disconnecting from Levelogger PC Software, the Wellhead draws about 3 mA
from the SDI-12 equipment, while waiting to connect to the SDI-12 network.
After the first SDI-12 command is received, the Wellhead idles around 30 uA.
NOTE
For more information about the
AquaVent loggers, Wellheads and
Vented Cables, see the Vented
Dataloggers User Guide.
Wire Colour SDI-12 Function Connection
Red 12 Volt Line +12V DC at SDI-12 Master
Black Ground Line Ground at SDI-12 Master
White Serial Data Line SDI-12 Data at SDI-12 Master
Table 1-1 SDI-12 Interface Cable Wire Definitions
The communication settings for the SPX Wellhead hardware comply with the
SDI-12 standard at 1200 baud, 1 start bit, 7 data bits, 1 parity bit (even parity),
and 1 stop bit.