6.2 Check the Wiring
If the user is unable to get a response from the Hydra Probe it is recommended to first physically
check wire connections from the probe to the logger. Check the cable for cuts and abrasions.
6.3 Logger Setup
If the connections are sound, the user will need to check the logger’s setup. Programming a data
logger is not a trivial task. The data logger needs to extract the data from data ports on the logger
with the desired timing interval. The logger is often times the power source for the probes. The
user may also want to cycle the power to the probe by disconnecting and reconnecting power.
Are the data ports enabled? Are the data ports scaled properly in the appropriate units? Are the
probes and logger adequately powered? Is the data properly reported and archived on the
logger’s firmware?
If the logger has GUI based operation software, there may be a help
function. If the logger only accepts terminal command scripts in a terminal window, refer to the
logger’s manual or manufacturer. Also, make sure the computer is properly connected to the
logger.
Is the computer on the proper COM port? What about the Baud rate? Does the logger
need a NUL modem or optical isolator in order to be connected to a computer?
Most of the
technical support questions Stevens receives are not due to malfunctioning probes but rather an
incorrect data logger setup.
DOTSet is a Windows program used to program a Stevens DOT Logger. Please refer to
Appendix C for more information about programming DOT Loggers.
6.4 Soil Hydrology
Sometimes the soil moisture data may look incorrect when in fact the Hydra Probes are
accurately measuring the actual soil moisture gradient. Soil Hydrology is complex and can be
modeled by Darcy’s Law and Richard’s Equation. These involved theories are beyond the scope
of this manual; however, knowledge of basic soil hydrology is worth discussing.
It’s important to note that the soil that resides between the tine assembly is where the
measurements are taken. If there is a void space in the soil between the tines, this will affect the
hydrology where the Hydra Probe is taking measurements. If the void space is saturated with
water, it will increase the soil moisture measurement. If the void space is not fully saturated, the
soil will appear dryer. Figure 6.1 shows the measurement volume where the Hydra Probe takes
measurements and a void space between the tine assembly. These void spaces can occur from a
poor installation, such as rocking the probe side to side or not fully inserting the probe into the
soil.
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