TDR SOIL MOISTURE MEASUREMENTS
6
3.5 GROUNDING
The TDR system should be installed with a
single ground point. A good earth ground
should be established close to the
datalogger/1502B.
A copper clad grounding rod comes with the
CM10 tripod or may be obtained along with
necessary clamps and wire from an electrical
supply house.
The ENC TDR has ground connections for the
datalogger, 1502B and 6590 Transient
Suppressor which are connected to a grounding
lug in the lower left corner of the enclosure. A
short run of heavy gage (10 AWG or lower) wire
should be connected from the lug to the earth
ground.
The ground lug on the multiplexer enclosures
should only be used if the multiplexer is close
enough to conveniently use the same ground
point as the datalogger.
3.6 BATTERY CONNECTIONS
Two terminal strip adapters for the battery posts
are provided with the ENC TDR (Figure 3-6).
These terminal strips will mount to the wing nut
battery posts on most deep cycle lead acid
batteries.
FIGURE 3-6. Terminal Strip Adapters for
Connections to Battery
4. PROGRAMMING INSTRUCTION 100
Instruction 100 is used to make TDR
measurements. A separate Instruction 100 is
entered for each multiplexer that has probes to
be measured or to measure separate groups of
probes on a single multiplexer.
Options in instruction allow:
finding a soil moisture probe automatically
or specifying the "distance" to the probe
calculating water content or storing raw
waveform data
the starting point and time resolution of the
raw waveform.
Instruction 100 may also be used to step
through the multiplexers while manually
controlling the 1502B to examine the
waveforms, and to check the signature of the
PROM in the SDM1502
INSTRUCTION 100 PARAMETERS
PAR.
DATA
NO.
TYPE
DESCRIPTION
01:
2
SDM1502 address
02:
2
Output option
0 Water content
1 Raw data
98 Manual step through
99 SDM1502 signature
03:
FP
Probe length, meters
04:
FP
Cable length, meters;
enter 0 for auto search
05:
4
Multiplexer channel/Reps
A B C D
A
Chan. of 1st Mux, 0 if none
B
Chan. of 2nd Mux, 0 if none
C
Chan. of 3rd Mux, 0 if none
D No. of Probes to scan
06:
4
Input location
07:
FP
Multiplier
08:
FP
Offset
Input Locations altered:
Water content - 1 per probe scanned
Raw data - 256 per probe scanned
Intermediate Locations required:
531 the first time Instruction 100 is used
16 intermediate locations for each
Instruction 100 thereafter.
Parameter 1, address: the address set into
the SDM1502 (Section 3.1).
Parameter 2 output option:
"Water Content", Code 0: the instruction
determines the end points of the probe using
the algorithm described by Baker and Allmaras,
