MPS-2 & MPS-6
5
CONNECTING TO A LOGGER
same 12 V supply and communication port on the data logger. This
simplifies wiring because no multiplexer is necessary. The drawback
to using multiple sensors on one bus is that a problem with a single
sensor can bring down the entire array (through a short circuit, etc.).
To avoid this problem, we recommend the user make an independent
junction box with wire harnesses where all sensor wires are wired to
wire lugs so sensors can be disconnected if a problem arises. A sin-
gle three-wire bundle can be run from the junction box to the data
logger.
Address
The SDI-12 protocol requires that all sensors have a unique address.
MPS-2 and MPS-6 sensors come from the factory with an SDI-12 ad-
dress of 0. To add more than one SDI-12 sensor to a bus, the sensor
address must be changed. Address options include 0...9, A...Z, a...z.
The best and easiest way to change an address is to use Decagon’s
ProCheck (if the ProCheck does not have this option, please up-
grade your firmware to the latest version). SDI-12 addressing can
be accessed in the “CONFIG” menu by selecting “SDI-12 Address.”
Addresses may then be changed by simply pressing the up or down
arrows until you see the desired address and pushing “Enter.”
Power
Customers can power the sensor with any voltage from 3.6 to 15
VDC, but 12 V is the optimal voltage. When using the sensor as
part of an SDI-12 bus, we recommended you excite the sensors con-
tinuously to avoid issues with initial sensor startup interfering with
the SDI-12 communications.
Reading
SDI-12 communication allows communication of many parameters at
once. This allows you to see information such as the sensor model,
SDI-12 version, temp, etc. Reading the sensor in SDI-12 mode re-
quires function calls.
19
