Communication; Sdi-12 Communication - Decagon Devices SRS Operator's Manual

Spectral reflectance sensor

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SRS Sensors

5 COMMUNICATION

Communication

The SRS communicates using SDI-12 protocol. This chapter dis-

cusses the speciﬁcs of SDI-1 Communication. For more information,

please visit www.decagon.com/support for an integrator's guide that

gives more detailed explanations and instructions.

5.1

The SRS communicates using the SDI-12 protocol, a three-wire in-

terface where all sensors are powered (white wire), grounded (bare

wire) and communicate (red wire) on shared wires (for more info,

go to www.sdi-12.org). There are some positive and negative ele-

ments of this protocol. On the positive side, multiple sensors can be

connected to the same 12 V supply and communication port on the

data logger. This simpliﬁes wiring because no multiplexer is neces-

sary. On the negative side, one sensor problem can bring down the

entire array (through a short circuit, etc.). To mitigate this problem,

we recommend the user make an independent junction box with wire

harnesses where all sensor wires are connected to binding posts so

you can disconnect sensors if a problem arises. A single three-wire

bundle can be run from the junction box to the data logger.

The SDI-12 protocol requires that each sensor have a unique ad-

dress. The SRS comes from the factory with an SDI-12 address of

0. To add more than one SDI-12 sensor to a system, the sensor ad-

dress must change. Address options include 0-9, A-Z, a-z. There are

two ways to set the SDI-12 sensor address. The best and easiest is

to use Decagon's ProCheck (if the option is not available on your

ProCheck, please upgrade to the latest version of ﬁrmware). Ac-

cess SDI-12 addressing in the "CONFIG" menu by selecting "SDI-12

Address" and pressing Enter. To change the SDI-12 address, press

the up and down arrows until you see the desired address and push

Enter. SDI-12 communication allows many parameters to be com-

municated at once, so you can also see things like the sensor model,

SDI-12 version, etc.

Campbell Scientiﬁc data loggers, like the CR10X, CR1000, CR3000,

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