Campbell TDR100 Instruction Manual - page 24
TDR100
14
Campbell Scientific recommends using datalogger switched 12 volts to power
the TDR100. This will provide power savings and will automatically reset the
TDR100 and provide automatic recovery from system malfunctions. This
practice can reduce loss of measurement data when a problem exists. Typically
the switched 12 volts is turned on at the beginning of the datalogger program
table that contains the TDR measurement instructions, and it is turned off at the
end of the table. The SW12() CRBasic instruction can be used to switch 12
volt power on the CR6, CR800, CR850, CR1000, or CR3000 datalogger. See
CR1000 programming example in the program example section of this manual.
7.2.5.1 Grounding
The TDR system should be installed with a single ground point. A good earth
ground should be established close to the datalogger/TDR100.
A copper clad grounding rod comes with the model CM106B tripod. The
UTGND kit provides hardware needed for grounding rod use.
The dataloggers, TDR100, SDM8X50, and SDMX50SP multiplexer have
grounding lugs. These lugs should be tied together with short pieces of
grounding wire no smaller than 12 AWG. The ENCTDR100 has a grounding
lug in the lower left corner of the enclosure. A piece of 10 AWG is provided
for connection to the components in the enclosure. A short run of heavy gage
(10 AWG or heavier) wire should be connected from the enclosure lug to earth
ground.
The ground lug on peripheral SDM8X50 and SDMX50 multiplexer enclosures
should only be used if the multiplexer is close enough to conveniently use the
same ground point as the datalogger.
7.2.6 SDM Communication
7.2.6.1 SDM Addressing for TDR100 System
SDM (Synchronous Device for Measurement) communication protocol is used
with the TDR100, SDM8X50, SDMX50, and Campbell Scientific dataloggers
to control measurements and transfer data. On our CR6, CR800 series, and
CR1000 dataloggers, the ports labeled C1, C2, and C3 are dedicated to SDM
functions DATA, CLOCK, and ENABLE, respectively. On our CR3000, the
ports are labelled SDM-C1, SDM-C2, and SDM-C3. The use of synchronous
communications requires adherence to an addressing scheme for all
communicating devices.
SDM cables have five conductors. The red and black wires are typically used
for 12 Vdc and ground. The remaining three wires connect the control lines.
One is used to connect C1 or SDM-C1 of the datalogger to C1 of each of the
other components of the system, e.g., TDR100 and SDM8X50 or SDMX50
multiplexer. Another wire is used to connect C2 or SDM-C2 of the datalogger
to C2 of the other system components. The last wire is used to connect C3 or
SDM-C3 of the datalogger to C3 of the other system components. If PC-TDR
is being used to control multiplexers, the control lines connect C1, C2, and C3
of TDR100 and multiplexer(s).
The SDM address of the TDR100 is set using the thumbwheel switch on the
TDR100 front panel. The address selected on the TDR100 must match the
SDM Address used in the datalogger program.